synthesis and characterization of fluorene based oligomers ... · synthesis and characterization of...
TRANSCRIPT
SYNTHESIS AND CHARACTERIZATION OF FLUORENE BASED OLIGOMERS AND POLYMERS
CAI LIPING
(MSc LANZHOU Univ.)
A THESIS SUBMITED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
DEPARTMENT OF CHEMISTRY NATIONAL UNIVERSITY OF SINGAPORE
2009
i
ACKNOWLEDGEMENTS
My most sincere gratitude goes out to my supervisor, Assoc. Prof. Lai Yee Hing, who
gave me the opportunity to purse a Ph. D. degree in the National University of Singapore
(NUS). Thanks him for his invaluable guidance, constant encouragement and great
support throughout my study. I gratefully appreciate the freedom he gave me to delve
into various aspects of this research.
The memories of my good times in the laboratory with Dr. Xu Jianwei, Dr. Wang Fuke,
Dr. Wang Weiling, Dr. Teo Tang Lin, Mr. Wang Jianhua, Mr. LuYong, Mr. Fang Zhen,
Mr. Chen Zhongyao and Mr. Wee Chorng Shin will remain with me forever.
I would like to thank the staffs at the chemical store and the Chemical and Molecular
Analysis Center of Chemistry Department for their technical assistance in various
analyses such as NMR, MS, EA. Special thanks also goes to the National University of
Singapore for awarding me a research scholarship.
Lastly, special mention must be made to my father, mother and wife. Thank them for
their deep loving encouragement and patience. Thank you.
Table of Contents
Acknowledgement i
Table of Contents ii
Summary vii
List of Tables ix
List of Figures x
Chapter 1 Introduction 1
1.1 Conjugated polymers 1
1.1.1 Structure of conjugated polymer 1
1.1.2 Bandgap of conjugated polymers 5
1.1.3 Fluorecence from conjugated polymers 7
1.1.4 Application of conjugated polymers 12
1.2 Polyfluorene as light emitting polymer 13
1.3 Organic light emitting diodes (OLED) 15
1.3.1 Hole transporting material, HTM 15
1.3.2 Electron transporting material (ETL) 21
1.3.2.1 Organometallic ETL compounds 21
1.3.2.2 Non-Organometallic ETL compounds 23
1.3.3 Bule light emitting materials 28
1.3.4 Green light emitting materials 34
1.3.5 Red light emitting materials 38
1.3.6 Hole Blocking materials 44
ii
1.4 Project objectives 46
Reference 51
Chapter 2 Synthesis and Characterization of Chromophore-Side
Chains PPV Derivatives 64
2.1 Introduction 64
2.1.1 Main synthesis routes of PPV compounds 64
2.1.1.1 Sulfonium precursor route 64
2.1.1.2 Side chain derivatization 65
2.1.1.3 Polycondensation methods 66
2.1.1.4 Ring-opening metathesis polymerization (ROMP) 67
2.1.2 Application of PPV and Derivatives 68
2.2 Molecular design 68
2.3. Synthesis route 69
2.4 Results and discussion 72
2.4.1 Polymer synthesis 72
2.4.2 Size exclusion chromatography (SEC) 73
2.4.3 Thermal Analysis (TGA and DSC) 74
2.4.4 Optical Properties (UV and PL) 75
2.4.5 Electrochemical Properties 77
2.4 Conclusion 78
Reference 80
iii
Chapter 3 Synthesis and characterization of tetrabenzo[5.5]fulvalene
based polymers 83
3.1 Introduction 83
3.2 Molecular design 84
3.3 Results and discussion 87
3.3.1 Size exclusion chromatography (SEC) 87
3.3.2 Thermal Analysis (TGA and DSC) 87
3.3.3 Optical Properties (UV and PL) 89
3.3.4 Electrochemical Properties 91
3.3.5 Comparison of our novel polymers with some analogues 92
3.4 Conclusion 93
Reference 94
Chapter 4 Synthesis and Characterization of Chromophore Substituted
[2.2]Paracyclophane Derivatives 96
4.1 Introduction 96
4.1.1 Cyclophane-containing Polymers 96
4.1.1.1 [2.2] Paracyclophane-containing polymers 97
4.1.1.2 Rigid-rod conjugated polymers containing
pendent aromatic rings 98
4.1.2 Cyclophane chiral ligands 100
4.1.3 Cyclophane nonlinear optical materials 101
4.1.3.1 Synthesis and characterization of chromophores
iv
substituted [2.2]paracyclophanes 102
4.1.3.2 Two photon absorption (TPA) performance
of paracyclophenes 103
4.1.3.3 Charge transport through paracyclophanes 104
4.2 Molecular Design 105
4.3 Synthesis and characterization 107
4.3.1 Synthesis of (4,7,12,15)-Terta(9,9-di-n-hexyl-fluoren-2-yl)
[2,2]paracyclophane (2F2F) 107
4.3.2 Synthesis of (4,7,12,15)-Terta(N-n-hexylcarbazole -3 -yl)
[2,2]paracyclophane (2C2C) and (4,7)-Bis(9,9-di-n-hexyl-
fluorene-2-yl)-(12,15)-bis(N-n- hexylcarbazole -3 -yl)
[2,2]paracyclophane (2F2C) 109
4.3.3 Synthesis of (4,7)-Bis(9,9-di-n-hexyl-fluoren-2-yl)-(12,15)-
bis(thiophene-2-yl) [2,2]paracyclophane (2F2T) and (4,7)-
Bis(N-n-hexylcarbazole-3-yl)-(12,15)-bis(thiophene-2-yl)
[2,2]paracyclophane (2C2T) 112
4.4 Results and Discussion 114
4.4.1 Synthesis methodology 114
4.4.2 NMR spectrum 117
4.4.3 MALDI-TOF mass spectrum 120
4.4.4 Optical Properties (UV and PL) 123
4.4.5 Electrochemical Properties 130
4.5 Conclusion 133
v
Reference 134
Chapter 5 Synthesis and Characterization of Hexafluorenyl Benzene 140
5.1 Introduction 140
5.2 Molecular design 141
5.3 Results and discussion 144
5.3.1 NMR spectroscopy 144
5.3.2 MALDI-TOF mass spectrum 146
5.3.3 Thermal Analysis (TGA and DSC) 147
5.3.4 Optical Properties (UV and PL) 149
5.3.5 Electrochemical Properties 150
5.4 Conclusion 151
Reference 153
Chapter 6 Experimental Section 154
6.1 Monomers and Polymers Synthesized in Chapter Two 154
6.2 Monomers and Polymers Synthesized in Chapter Three 162
6.3 Molecules Synthesized in Chapter Four 167
6.4 Molecules Synthesized in Chapter Five 178
Reference 183
Appendix I Characterization techniques I
vi
Summary
Organic conjugated polymers have been thoroughly investigated over the past twenty
years due to their promising electronic and optical applications. Current research interests
on conjugated polymers focus on tuning their spectral and electrical properties. During
these researches, polyfluorene emerged as a very attractive class of conjugated polymers,
especially for display applications, owing to their pure blue and efficient
electroluminescence coupled with a high charge-carrier mobility and good processability.
In our work, four series of fluorene based new polymers and oligomers will be reported.
In the work of PPV derivatives polymers synthesis (Chapter two), two novel
dichromophore side chains substituted PPV compounds were successfully synthesized.
Two key steps in the whole synthesis route were aromatic CH2Br groups’ protection and
deprotection reactions. The high yields of these two reactions were guarantee of the
success of whole route. Efficient green light emission, good solubility in common organic
solvents, good thermal stability and relative high glass transition temperatures had been
demonstrated in these two polymers. These properties made the two polymers good
candidates for efficient green light emitting devices
In order to investigate the effect of bistricyclic aromatic system on the polymer
backbone, two novel tetrabenzo[5.5]fulvalene units containing polymers were
successfully synthesized (Chapter three). Good solubility in common organic solvents,
good thermal stability and relative high glass transition temperatures had been
demonstrated in these two polymers. Although the quantum yield of the two polymers
were low due to the good packing of the tetrabenzo[5.5]fulvalene units. These
vii
compounds can still have the potential to be used as solar cell and organic field effect
transistor materials.
Compared with polymers, oligomers generally have more predictable and reproducible
properties that are amenable to have optimization through molecular engineering. In our
work of Chapter four, five tetra-substituted [2.2]paracyclophane oligomers were obtained
in high yields. Two key step reactions, which are HBr gas deprotecting reaction and UV
irradiation reaction, gave satisfactory yield of whole synthesis route. Efficient blue light
emission, good solubility in common organic solvents had been demonstrated in all of the
five compounds. The optical and electrochemical properties all exhibited dependence on
the changes of different substituted chromorphores on the [2.2]paracyclophane core.
Modification on the substitution groups with different electron-donating and electron-
withdrawing groups on the [2.2]paracyclophane core enabled the tuning of HOMO and
LUMO energy levels. This freely modification makes the synthesis route very useful to
obtain different [2.2] paracyclophanes derivatives which can be used in different
applications areas such as asymmetric reaction, OLED and NLO materials.
In our last chapter work, a convenient approach to synthesize high steric hindrance
hexafluorenyl benzene was successfully established (Chapter Five). Detailed reaction
conditions were discussed. This compound can be a theory model of conformational
mobile system.
In conclusion, by the different synthetic modification, fluorene based polymers and
oligomers can be more useful in different materials application.
viii
List of Tables
Tables Page
Table 1.1 Some Important Conjugated Polymers 2
Table 2.1 The SEC data of polymer P1 and P2 73
Table 2.2 The optical data and fluorescence quantum yields
(both in chloroform solutions) of polymer P1 and P2 76
Table 2.3 The electrochemical data of the polymers P1 and P2 78
Table 3.1 The SEC data of polymer P1 and P2 87
Table 3.2 The optical data and fluorescence quantum yields
(both in chloroform solutions) of polymer P1 and P2 90
Table 3.3 The electrochemical data of the polymers P1 and P2 91
Table 4.1 The optical data of [2.2]paracyclophanes and their precursors
[3.3]dithioparacyclophane in chloroform solution 129
Table 4.2 The electrochemical data of [2.2]paracyclophanes and their
[3,3]dithioparacyclophane precursors in chloroform solution 132
Table 5.1 The optical data and fluorescence quantum yields
(both in chloroform solutions) of compound 1c and 3c 150
Table 5.2 The electrochemical data of the polymers 3c 151
ix
List of Figures
Figures Page
Figure 1.1 Fig 1.1 A schematic representation of energy gap
in metal, insulator and semiconductor 6
Figure 1.2 Relationship between absorption, emission and
nonradiative vibration processes 8
Figure 1.3 The scheme for photoluminescence (PL) and
electroluminescence (EL) of conjugated polymers. 9
Figure 1.4 The Schematic diagram of the EL process 11
Figure 1.5 Synthesis of 9, 9-dialkyl-PF according to Yamamoto reaction 15
Figure 1.6 Synthesis of bicarbazole HTM materials 16
Figure 1.7 C-N bond coupling by Buchwald – Hartwig Reaction 17
Figure 1.8 Triphenylamine and thiophene units in HTM materials 18
Figure 1.9 3,6-disubstituted and N-substituted carbazole units in HTM materials 18
Figure 1.10 Star-shape thiophene and triphenylamine units in HTM materials 19
Figure 1.11 Diels-Alder reaction in the synthesis of HTM materials 20
Figure 1.12 Furan units in HTM materials 20
Figure 1.13 Some of the Organometallic ETL compounds 21
Figure 1.14 Oxadiazole and benzoimidazole units in ETL materials 22
Figure 1.15 Pyrimidine units in ELT materials 23
Figure 1.16 Triazene units in ETL materials 24
Figure 1.17 Silole units in ETL materials 25
Figure 1.18 Boride and per-fluorobenzene units in ETL materials 25
x
Figure 1.19 Thiophenesulfone, cyclooctatetraene and
diarylfluorene units in ETL material 26
Figure 1.20 Spirobifluorene units in blue light emission materials 28
Figure 1.21 Steric hindrance groups in blue light emission materials 29
Figure 1.22 Stilbene units in blue light emission materials 30
Figure 1.23 Tetra-phenyl substituted stilbene and coumarine structure units
in blue light emission materials 31
Figure 1.24 Oxadiazole units in blue light emission materials 31
Figure 1.25 Coumarin units in green light emission materials 32
Figure 1.26 Oxazolinone and pyrrole units in green light emission materials 33
Figure 1.27 Diphenylamine units in green light emission materials 34
Figure 1.28 Oxadiazole and nitrile units in green light emission materials 35
Figure 1.29 Bipolarity molecular design in green light emission materials 36
Figure 1.30 Isophorone and chromene units in red light emission materials 37
Figure 1.31 Polyacene units in red light emission materials 38
Figure 1.32 Neutral red core in red light emission materials 39
Figure 1.33 ETL and HTL structure units in red light emission materials 40
Figure 1.34 Maleimide and benzothiazazole units in red light emission materials 41
Figure 1.35 BCP and Oxadiazole units in hole blocking materials 43
Figure 1.36 Diazofluorenone, star-shape fluorene and aryl silane
units in hole blocking materials 44
Figure 1.37 Chapters work diagram 47
Figure 2.1 The sulfonium precursor route (SPR) 65
xi
Figure 2.2 The Gilch route 66
Figure 2.3 Ring-opening metathesis polymerization (ROMP) route 67
Figure 2.4 Protection and deprotection of -CH2Br group
on difluorenyl benzene ring 72
Figure 2.5 The thermalgravimetric analysis (TGA) of Polymer
P1 and P2 in a nitrogen atmosphere 74
Figure 2.6 The DSC traces of Polymer P1 and P2 75
Figure 2.7 The UV-vis absorption spectra and photoluminescence spectra
of Polymer P1 and P2 measured from their chloroform
solution at room temperature 76
Figure 2.8 Solvent effection on linear photoluminescence spectra of polymer P1 77
Figure 2.9 The cyclic voltammograms of P1 and P2 78
Figure 3.1 The thermalgravimetric analysis (TGA) of P1 & P2
in a nitrogen atmosphere 88
Figure 3.2 The DSC traces of P1 and P2 88
Figure 3.3 The UV-vis absorption spectra and photoluminescence spectrum
of Polymer P1 and P2 measured from their chloroform
solution at room temperature 90
Figure 3.4 The cyclic voltammograms of P1 and P2 91
Figure 4.1 Paracyclophane 96
Figure 4.2 Conjugated polymers including oligothiophene
xii
and [2.2]paracyclophane units 97
Figure 4.3 Main-chain-type [2.2]paracyclophane-containing
conjugated polymers 97
Figure 4.4 Dithia[3.3]paracyclophane-fluorene copolymers 99
Figure 4.5 The detection of Mn+ by dithia[3.3]paracyclophane-fluorene polymers 100
Figure 4.6 [2.2]Paracyclophane substitution patterns and ligands 100
Figure 4.7 Tetra- substituted Cyclophanes 102
Figure 4.8 Quadrupolar cyclophane systems 104
Figure 4.9 Cyclophane molecular structures used for charge transport 104
Figure 4.10 Normal ways to construct cyclophane derivatives structures 105
Figure 4.11 Retrosynthetic analysis of target tetrasubstituted [2.2]paracyclophane 106
Figure 4.12 Protection and deprotection of -CH2Br group on the benzene ring 115
Figure 4.13 Synthesis of [2.2]paracyclophanes from
[3.3]dithioparacyclophanes precursors 116
Figure 4.14 NMR spectrum of five target [2,2]paracyclophanes 119
Figure 4.15 The different protons on cyclophane core bridge -CH2 groups 120
Figure 4.16 MLDI-TOF mass spectrum of all final [2.2]paracyclophanes 123
Figure 4.17 The UV-vis absorption spectra and photoluminescence
spectra of DiS2F2F(11) and 2F2F(12) measured from
their chloroform solution at room temperature 124
Figure 4.18 The UV-vis absorption spectra and photoluminescence spectra
of DiS2C2C(20) and 2C2C(21) measured from their chloroform
solution at room temperature 125
xiii
Figure 4.19 The UV-vis absorption spectra and photoluminescence spectra
of DiS2F2C(22) and 2F2C(23) measured from their chloroform
solution at room temperature. 126
Figure 4.20 The UV-vis absorption spectra and photoluminescence spectra
of DiS2F2T(28) and 2F2T(29) measured from their chloroform
solution at room temperature 127
Figure 4.21 The UV-vis absorption spectra and photoluminescence spectra
of DiS2CT(30) and 2C2T(31) measured from their chloroform
solution at room temperature 128
Figure 4.22 The cyclic voltammograms of DiS2F2F(11) and 2F2F(12) 130
Figure 4.23 The cyclic voltammograms of DiS2C2C(20) and 2C2C(21) 130
Figure 4.24 The cyclic voltammograms of DiS2F2C(22) and 2F2C(23) 131
Figure 4.25 The cyclic voltammograms of DiS2F2T(28) and 2F2T(29) 131
Figure 4.26 The cyclic voltammograms of DiS2C2T(30) and 2C2T(31) 131
Figure 5.1 Structure of star-shaped oligomers with truxene and benzene core 140
Figure 5.2 Normal ways to synthesize di-R group substituted alkyne 143
Figure 5.3 Proposed mechanism of Cycloaromatization by using Co2(CO)8 144
Figure 5.4 1H and 13C spectra of target molecule 3c 145
Figure 5.5 MALDI-TOF mass spectrum of target molecule 3c 147
Figure 5.6 The thermalgravimetric analysis (TGA) of 3c 148
Figure 5.7 The DSC traces of 3c 149
xiv
Figure 5.8 The UV-vis absorption spectra and photoluminescence spectra
of 3c and 1c measured from their chloroform solution
at room temperature 149
Figure 5.9 The cyclic voltammograms of 3c 151
xv
1
Chapter One
Introduction
1.1 Conjugated polymers
In 1977 Shirakawa’s group found that the conductivity of polyacetylene can be
increased significantly by doping it with various electron acceptors or electron donors.1
This discovery inspired an intensive investigation of highly conjugated organic polymers.
Many chemists and physicists considered the possibility of using organic polymers as
conductors. In the past three decades, various conjugated polymers, which have different
electrical,2 magnetic3 and optical properties4 owing to the substantial π-electron
delocalization along their backbones have been synthesized. Today, conjugated polymers
have been an active multidisciplinary research field not only because of their theoretically
interesting properties but also because of their technologically promising future.
1.1.1 Structure of conjugated polymer
Conjugated polymers can be characterized by the alteration of double (or triple) and
single bonds along the skeleton chain, and are indicative of a σ-bonded C-C backbone
with π- electrons delocalization. Such delocalization is the origin of semiconducting or
conducting properties of conjugated polymers. The combination of the properties of the σ
and π electrons allows these polymers to survive in a wide range of oxidation and
reduction states. These properties made them to be good candidates of electrochemical
insertion electrodes, high-conductivity/low-density metals, materials for non-linear optics
and as semiconductors.5-8 The chemical structures of some important conjugated
polymers are listed in Table1.1. 9
Table 1.1 Some Important Conjugated Polymers
Polymers Chemical Name Formula Bandgap(eV)
PA trans-polyacetylene n
1.5
PPP poly(p-phenylene) n
3.3
PF polyfluorene
R'R n
3.2
PPV poly(p-phenylenevinylene)
n
2.5
RO-PPV Poly(2,5-dialkoxy-p-phenylenevinylene)
n
OR
RO
2.2
PPE poly(p-phenylene
ethynylene) n
2.8
PT polythiophene S
Sn
2.0
P3AT poly(3-alkylthiophene) S
S
R
Rn
2.0
PPy polypyrrole NH n
3.1
PANI polyaniline HN
n
3.2
2
Polyacetylene (PA) is a prototypical example of this type of materials. Due to the
simplicity of its structure, it has been used as a model material for both theoretical and
experimental studies.10 The spin or charge-carrying segments of PA were viewed as
perturbations or as excitations in very long or infinite PA (CH)n chains. Such an
excitation can be described as a solitary wave of a fixed shape that can move along PA
chains. Such spin- or charge-density waves are classified as quasi- or pseudo- particles
and are called solitons.11 The Polymer PA can exist in several isomeric forms and the
trans-isomer, usually referred to as “trans-polyacetylene”, is a thermodynamically stable
isomer at room temperature.12
Poly(p-phenylene) and its derivatives(PPPs) have found considerable interest over the
past years since it acts an excellent organic conductor upon doping whereas neutral PPP
is a good insulator. A second major interest arises from the fact that PPP can be used as
the active component in blue light-emitting diodes (LEDs).13 Oligo(p-phenylene) have
played a dominant role as model compounds for PPPs in the study of physical
mechanisms related to intra- and inter-chain charge transport or distribution and
stabilization of charges and spins on π-conjugated chains. These mechanisms are of
special interest with regard to the potential application of PPP in rechargeable batteries.14
Poly(p-phenylenevinylene) and its derivatives (PPVs) are among the most extensively
studied systems since the first reported light-emitting devices(LEDs)15 using PPV as the
emission layer. The tremendous advantages in chemistry and physics of PPVs over recent
years have stimulated further interest in related types of structure such as poly(p-
phenyleneethylene) (PPE) polymers, which exhibit large photoluminescence efficiencies
3
both in the solid state as a consequent of their high degree of rigidity, and their extremely
stiff, linear backbones.16
Polythiophene (PT), polypyrrole (PPy) and their derivatives are among the most
widely studied types of π-conjugated polymers. In these polymers, N and S atoms
provide p orbitals which can couple with conjugated segments for continuous orbital
overlap. The N and S atoms are also necessary for these polymers to become electrically
conducting.12,2 In comparison to PA, PT and PPy provide higher environmental stability
and structural versatility. Polyanilines (PANI) and its oligomers have also attracted a
great deal of research interest towards their application in the field of conducting
polymers.12
Although the semiconducting behavior of conjugated polymers is easily understood
from the bonding, a polymer must satisfy two conditions for it to work as a
semiconductor.17,18 One is that the σ bonds should be much stronger than the π bonds so
that they can hold the molecule intact even when there are excited states, such as
electrons and holes, in the π bonds. These semiconductor excitations weaken the π bonds
and the molecule would split apart were it not for the σ bonds. The other requirement is
that π-orbitals on neighboring polymer molecules should overlap with each other so that
electrons and holes can move in three dimensions between molecules. Fortunately many
polymers satisfy these three requirements. Most conjugated polymers have
semiconductor band gaps of 1.5-3.0 eV, which means that they are ideal for
optoelectronic devices which emit light.
4
1.1.2 Bandgap of conjugated polymers
According to the band theory,19 the electrical properties of inorganic semiconductors
are determined by their electronic structures as the electrons moving within discrete
energy states which are called bands. For the conjugated polymers, their electronic and
optical properties are mainly determined by its π-electron system. In the ground state, the
π-electrons have a series of energetic levels that together form the π-bonds. The highest
energy π-electron level is referred to as the highest occupied molecular orbital (HOMO).
In the excited state, the π-electrons form the π* band. The lowest energy π*-electron level
is referred to as the lowest unoccupied molecular orbital (LUMO). The HOMO and
LUMO are known as the frontier orbitals. The energy difference between the highest-
occupied π band and the lowest unoccupied π* band is the π-π* energy band gap.
Electrons must have a certain energy to occupy a given band and need extra energy to be
excited enough to move from the valence band to the conduction band. In addition, the
bands should be partially filled in order to be electrically conducting because all empty
and fully occupied bands can not carry electricity. Owing to the presence of partially
filled energy bands, metals have high conductivities (Figure 1.1).20
Increasingenergy
Metal Insulator Semiconductor
Wide band gapNarrow band gap
Energy levels in conduction band
Energy levels in valence band
5
Fig 1.1 A schematic representation of energy gap in metal, insulator and semiconductor
When measured experimentally, the HOMO and LUMO all have a continuous
distribution. The top edge of the HOMO distribution corresponds to the ionization
potential (IP) of the molecule, and the bottom edge of the LUMO distribution
corresponds to the electron affinity (EA). The values of IP and EA are important
parameters for an OLED material because they determine the rate of hole and electron
injection.
Measurement of the energy of the HOMO of small molecules is done with ultraviolet
photoelectron spectroscopy (UPS). For polymeric materials which can not be thermally
deposited, electrochemical measurement of molecular electronic levels is required.21 This
technique is the cyclic voltammetry (CV). CV gives the values of the oxidation and
reduction potentials for a material in solution relative to a reference redox couple.
However, these values may not be equivalent to the true IP or EA. In solution, the
electronic structure of a molecule may be altered by the polarity of its surrounding. The
conformational freedom of a molecule in solution makes the addition or removal of an
electron easier than that for the condensed material. Then the energy gap between the
oxidation and reduction potentials measured electrochemically is usually slightly larger
than the optical energy gap for a conjugated polymer. By now, CV is still the best way
used as a relative measurement of the electronic levels for conjugated polymers.
Conjugated polymers generally have band gaps with in the range of 1.0-4.0 eV.22,23
The band gap of a conjugated polymer increases when its π-electrons become more
highly confined. In polymers where the wavefunctions are highly delocalized, the band
gap is largely determined by the degree of bond alternation. The key of obtaining small
6
band gap conjugated polymers is to design the chemical structure in such a way to
minimize the bond alternation. An example of this is polyisothianaphene(PITN), which
has a band gap of only 1.1 eV because it has an aromatic ring appended to its backbone
thiophene unit to reduce the bond alternation.23,24
PPP and PITN represent the extreme cases: PPP has a large band gap because its
excited state wavefunctions are localized to one repeat unit; PITN has a small band gap
because of its highly delocalized π-electrons and its minimal bond alternation. By tuning
the bond alternation and the torsion angles between rings in the polymer backbone, the
band gap of conjugated polymers can be tuned in fine increments from 1.0 eV to 4.0 eV.
1.1.3 Fluorescence from Conjugated Polymers
Conjugated polymers possess conjugated backbones, which allow π-electrons to be
delocalized extensively along the chain. The conjugated backbones in these polymers can
also be regarded as an extreme example of a long-chain chromophore. Most conjugated
polymers appear colored and show interesting photophysical phenomena, such as
photoconductivity,25 nonlinear optical properties (NLO) 5 and photoluminescence (PL).26
Figure 1.2 shows the relationship between absorption, emission and nonradiative
vibration processes.27
When a conjugated polymer is irradiated by light, photoexcitation of an electron from
the highest occupied molecular orbital (HOMO) (or ground state S0) to the lowest
unoccupied molecular orbital (LUMO) generates an excited state (S1) in which the
electron will lose the absorbed energy in the following ways: (1) Radiationless transitions,
such as internal conversion or intersystem crossing; (2) Emission of radiation, such as
7
fluorescence; (3) Photochemical reactions, such as rearrangements and dissociations. In
the excited state, some energy in excess of the lowest vibration energy level is rapidly
dissipated and the lowest vibration level of the excited singlet state is attained. If all of
this excess energy is not further dissipated by collisions, the electron returns to the
ground state with the emission of energy. This phenomenon is called fluorescence.
Consequently, much of the light energy absorbed by conjugated polymers may be lost by
processes other than fluorescence. Indeed, it is rare for conjugated polymers to emit all of
its absorbed energy as light. As shown in Fig 1.2, in most cases, the energy of emitted
light (hυe) is lower than that of the originally absorbed light (hυa). This difference
between absorbed and emitted light is termed as the Stokes shift.
S0
S1
S2
T1
T2
a fluorescence
b phosphorescence
a b
Singlet state Triplet state
intersystem
crossing
Radiation transition
Nonradiation transition
Vibration state
Electron state
Fig 1.2 Relationship between absorption, emission and nonradiative vibration processes
8
LUMO
HOMO
Interchainphotoexcitation
singlet excitonradiative decay
hvPL hv'
hv'
Electroninjection Recombination
Holeinjection
(-) polaron Singlet excitonradiative decay
(+) polaron
Cathode
Anode
EL
e-
e-
Fig. 1.3 The scheme for photoluminescence (PL) and electroluminescence (EL) of conjugated polymers The property of photoluminescence (PL) makes conjugated polymers suitable for the
application as active elements in polymer light-emitting diodes (PLEDs). In order to
understand the principles behind light emission in PLEDs, it is important to begin with
the simpler process of PL28 and realize the similarity between PL and
electroluminescence (EL)29 emission spectrum. The process of PL and EL are compared
in Figure 1.3.28 In PL, light is converted into visible light using an organic compound as
the active material whereas in EL, the organic compound converts an electric current into
visible light.30 Photoexcitation of an electron from the highest occupied molecular orbital
9
(HOMO) to the lowest unoccupied molecular orbital (LUMO) generates a single exciton
(a neutral excitation) which can decay radiatively with emission of light at a longer
wavelength (the Stocks shift) than that absorbed. Charged species (bipolarons) and triplet
excitons (detected by photo-induced absorption) provide the main channels for non-
radiative decay processes which can compete with and reduce efficiencies for radiative
decay of the singlet exciton.(Figure 1.4)31-33
Photoluminescence efficiency is an important property of photonic device. In polymers,
it is limited by two factors, one is the excimer formation and the other is existence of
quenching center.34 Excimer formation occurs when the backbones of neighboring chains
are very closely packed, which will result in a spectral red shift, spectral broadening and
inefficiency.35-37 The nature of quenching sites in polymers is not yet fully understood.
One type of quenching is the nonradiative recombination through carbonyl defects.38 A
small concentration of carbonyl defects can greatly reduce the efficiency of a polymer
because excitations migrate to find the defects, which have an energy level within the
band gap of polymer. Since the carbonyl defects form when conjugated polymers are
excited in the presence of oxygen, photonic devices are usually made in an inert
atmosphere and sealed in hermetic package.
10
Organicelectroluminescent
material
Polaronformation
Polaronformation
Electron/holerecombination
Exciton
25% S 75% T
Anode Cathode
Holeinjection
Electroninjection
Yield < 0.25 ( photoluminescence yield)
Fig 1.4 The Schematic diagram of the EL process33
The substituents on a conjugated polymer may have great effects on the fluorescence
property. Substituents which enhance the π-electron mobility will normally increase
fluorescence. A combination of electron-donating substituents with electron-withdrawing
substituents is also used to enhance fluorescence. PL can often be greatly enhanced by
increasing the intrinsic stiffness of a polymer backbone or by introducing large bulky side
groups to weaken intermolecular interaction.39 The close relationship between PL and EL
implies that increasing the ФFL will result in equal improvements in EL efficiency.
11
1.1.4 Application of Conjugated Polymers
Generally, the properties of the conjugated polymers can be mainly divided into two
parts. The one is focused on their reversible redox properties (i.e. electroactivity), while
the other is focused on their electrically conductive properties (i.e. conductivity). In the
first case, each application exploits the fact that the electrical and optical properties of
conjugated polymers depend on their level of oxidation or reduction in a controllable
manner. As a result, the conjugated polymers with this characteristic can be used as
electronic devices40, rechargeable batteries41, and drug release system. The combination
of electroactivity and reasonable stability in aqueous solution makes feasible the use of
selected conjugated polymers in the application of biomedical interest.42,43 Since the
conductivity of some conjugated polymers such as polyacetylene rise quite dramatically
with exposure to small amounts of “dopants”, they offer high sensitivity for detection of
these dopants.
In the area of sensors, considerable attention has also been directed towards
amperometric sensors, primarily for detection of glucose.44-46 It was also found that their
application as chemosensors,47 biosensors48 based on a variety of schemes including
conductormetric sensors49, potentiometric sensors, colorimetric sensors and fluorescent
sensors. In addition, conjugated polymers were also potential candidates as electrically
conducting textiles by incorporation of conductive fillers50 and candidates as artificial
muscles based on transition change caused dimensional changes.51 The use of conjugated
polymers in industrial separation is gaining increased popularity due to the cost and
energy conservation advantage. Electronically conducting polymers such as
polymethylpyrrole and polyaniline are promising materials for industrial gas separation.
12
On the other hand, the application simply takes advantages of electrical conductivity of
doped conjugated polymers, which makes them attractive alternatives for certain
materials currently used in microelectronics. The conductivity of these materials can be
tuned by chemical manipulation of the polymer backbone, by the nature of the dopant, by
the degree of doping, and by blending with other polymers. In addition, they offer
advantages such as light-weight, operability and flexibility which entitle them potential
application ranging from the device level to the final electronic products. It is reported
that polyaniline52, polyacetylene53 and polypyrrole54 can be widely used as conducting
resists in the lithographic applications, polyaniline as the materials for shielding
electromagnetic radiation and reducing or eliminating electromagnetic interference.55-57
One of the most advanced application of conducting polymers is their use as active
materials in photoelectronic devices, such as light-emitting diodes58, light-emitting
electrochemical cells,59,60 photodiodes61-63, field effect transitors,64-70, polymer rigid
triodes71, optocouplers72 and laser diodes73 etc. Some of these polymer-based devices
have reached performance levels comparable to or even better than those of their
inorganic counterparts. In addition, conjugated polymers can also be used for applications
such as electrostatic shielding, non-linear optics74,75, electrochromic windows76 and
photodetectors.77,78
1.2 Polyfluorene as Light Emitting Polymer
Alkylsubstituted polyfluorenes have emerged as a very attractive class of conjugated
polymers, especially for display applications, owing to their pure blue and efficient
electroluminescence with a high charge-carrier mobility and good processability. The
13
availability of specific and highly regioselective coupling reactions provides a rich
variety of tailored polyfluorene-type polymers and copolymers.
First attempts to synthesize soluble, processable poly(2,7-fluorene)s (PFs) via an
attachment of soluble substituents in 9-position of the fluorene core were published in
1989 by Yoshino and co-workers. They coupled 9, 9-dihexylfluorene79 oxidatively with
FeCl3 and obtained low molecular weight poly(9,9-dihexylfluorene) (PF6, Mn up to 5000,
Pn= 9-13). This oxidative coupling is not strictly regioselective, as structural defects are
created besides “regular” 2, 7-linkages.
The enormous progress in the availability of efficient and strictly regioselective
transition metal-catalyzed aryl-aryl-couplings has paved the way for the synthesis of high
molecular weight, structurally well-defined PF derivatives. Especially reductive aryl-aryl-
couplings of dihaloaryls according to Yamamoto reaction, aryl-aryl cross-couplings of
aryldiboronic acids (esters) and dihaloaryls according to Suzuki reaction or distannylaryls
and dihaloaryls according to Stille reaction have been successfully applied.
The first transition-metal catalyzed coupling of 2,7-dibromo-9,9-dialkylfluorenes
with NiII salt/zinc was described by Pei and Yang (Uniax Corp.) in 1996.80 Later on, a
research group at DOW Chemical Corp. 81 as well as Leclerc and co-workers82 published
the synthesis of 9,9-dialkyl-PFs following the Suzuki-type cross-coupling of 9,9-
dialkylfluorene-2,7-bisboronic acid or ester and 2,7-dibromo-9,9-dialkylfluorene
monomers.
Since the Suzuki-type coupling provides PFs with a maximum Mn of several 10000,
the Yamamoto-type coupling can lead to very high molecular PFs with a Mn of up to 200
000 (Pn: up to 500).83 The main prerequisite for reaching such high molecular weights is,
14
however, the use of carefully purified monomers and the application of optimized
reaction conditions. On the lab scale (up to 10 g batches), the application of Ni(COD)2 as
reductive transition metal-based coupling agent is very favorable (Figure 1.5 ).
Br Br
R R R R n
Ni(COD)2.
Fig 1.5 Synthesis of 9, 9-dialkyl-PF according to Yamamoto reaction
1.3 Organic Light Emitting Diodes (OLED)
OLED is a multiple layers thin film device. In an outside electric field, the emission
layer can form excited state and release energy by giving out light. This process is
electroluminescence (EL). The complicated device structure and different layers
materials requirements need the contribution of careful molecular design and synthesis
work.84 The properties of different devices layers and their synthesis works are presented
as follows. These summary are very useful not only in OLED but also in application of
other conjugated polymers.
1.3.1 Hole transporting material, HTM
In an OLED device, the hole transporting material is in the middle of anode and
emitting layer. It will help the hole transportation and injection into the emitting layer.
HOMO energy level of hole transporting materials should be near the potential of the
anode and be higher than the emitting layer. Most of the normal HTM materials are
triarylamine. According to the central core part of triarylamine, there are biphenyl,
15
starburst and spiro kinds of HTM. Copper catalyzed Ullmann coupling reaction is often
used in the synthesis of bicarbazole HTM materials(Figure 1.6).85-87
HN
N
I I
1,10-phenanthrolineCuCl, KOH, toluene,
85%
N
TPD
1
NH
HN
I
K2CO3, Cu2SO4
Decane
N
N
2
Fig 1.6 Synthesis of bicarbazole HTM materials
Palladium catalyzed Buchwald – Hartwig Reaction was widely used in the synthesis of
triarylamine to form C-N bond (Figure 1.7). 88-94
The key of the spiro HTM materials synthesis is the construction of the central core
which was synthesized from the bromides of the spiro compounds.95,96
N NNH
BrBr
Pd(OAc)2, P(t-Bu)3NaO-t-Bu, o-Xylene
92%
3
16
BrBr
Br Br
HN
NPh2Ph2N
Ph2N NPh2Pd(OAc)2, P(o-CH3Ph)3
NaO-t-Bu, toluene
4
BrBr
O
HN
Pd(OAc)2, P(t-Bu)3
NaO-t-Bu, Xylene
NPh2Ph2N
O
5
t-But-Bu1.
2. MeSO3H, AcOH
NPh2Ph2NLi
6
Fig 1.7 C-N bond coupling by Buchwald – Hartwig Reaction
The starburst HTL materials have high potential in the future application.97,98 With an
electron rich structure, thiophene compounds can also be used as HTL materials(Figure
1.8).
99
17
N NN
I
I
I
HN
N
N
Cu, KOH
7
S
S
Ph
Br
Ph
Br
HN
Ar
Pd(OAc)2, P(t-Bu)3NaO-t-Bu, toluene
S
S
Ph
N
Ph
NAr
Ar
8
Fig 1.8 Triphenylamine and thiophene units in HTM materials
The bromination reaction is easy to be processed on the 3, 6 position of carbazole.
From this carbazole dibromide, HTL materials with emitting properties can be obtained
by transition metal catalyzed C-N bond coupling reaction (Figure 1.9).100,101
N
Br Br
N
N
NNH
R
R R
Pd(dba)2, P(t-Bu)3NaO-t-Bu, toluene
9
18
NH
BrBr
CH3
H3C
N
CH3
H3C
N
Pd(OAc)2, P(t-Bu)3NaO-t-Bu, Xylene
10
Fig 1.9 3,6-disubstituted and N-substituted carbazole units in HTM materials
Some HTL materials have higher triplet state energy level, which can be used as the
phosphorescence emitting layer.102
Another synthetic method choose using metal substituents compounds to react with the
halogen core compounds.(For example, use Stille reaction to complete the synthesis of
starburst compounds).103
The homologue compounds with a thiophene core can be obtained by Kumada
coupling reaction.104,105 Triarylamines can also be obtained by aromatic electrophilic
substitution reaction (Figure 1.10).106
BrBr
BrBr
Br
Br
SBu3Sn N
Ph
Ph
S
NPh
Ph
S
N
PhPh
S N
Ph
PhS
N Ph
Ph
S
N
PhPh
SN
Ph
Ph
Pd(PPh3)2Cl2
11
19
N N NMgBr
SBr Brn S
n
n=1-4
12
BrBr
O
N
N
BrBr
NMeSO3H, 1700C
13
Fig 1.10 Star-shape thiophene and triphenylamine units in HTM materials
A high thermal stability HTL compounds can be obtained by Diels-Alder reaction
(Figure 1.11).107 Heterocycle compounds with high electron density have hole
transporting properties. The homologue compounds of thiophene and furan are often used
as HTL materials (Figure 1.12).108,109
O O O
O ON
N
N
H2N
Benzophenone1,2,4-trichlorobenzene
14
Fig 1.11 Diels-Alder reaction in the synthesis of HTM materials
20
SS
1. BuLi
2.
3. TFA
CHOOHCOO
15
Fig 1.12 Furan units in HTM materials
1.3.2 Electron transporting material (ETL)
Electron transporting materials (ETL) have higher electron affinity (low LUMO
energy level). ELT makes it easy for the electrons to be injected from cathode and match
the LUMO level of emitting layer, thus increases the efficiency of electron injection. In
addition, ETL needs higher ionization energy (low HOMO energy level) to limit holes in
the surface of emitting layer and ETL layer. For these properties, electron-withdrawing
groups or metal ion will be introduced into the synthesized ETL compounds. Normally
there are two kinds of ETL materials.
1.3.2.1 Organometallic ETL compounds
Some of the Organometallic ETL compounds are shown in Figure 1.13.
21
N
N
NO
O
O
Al
N
O N
OBe
O
NZn
N
O NO
NO
Al OH
N NNNZn
O
O
O
NN
O
N N
O
OZn
O
O
OO
O
O
Al
16 17 18 19
20 21 22
Fig 1.13 Some of the Organometallic ETL compounds
1, 3, 4-Oxadiazole is often used as the coordinating group. It can be synthesized from
hydrazine by cyclic condensation reaction.110-114 The coordinating group of
benzoimidazole is synthesized by dehydration-condensation reaction in high temperature
(Figure 1.14).115
O
N NHO
O
NH
HN
O OH
SOCl2
.
23
O
Cl
RN
N
NHN
O
N NR+
Pyridine
24
22
O OH
OCH3NH
NH2
N N
OH
1,2-dichlorobenzene
170-2200C+
25
Fig. 1.14 Oxadiazole and benzoimidazole units in ETL materials
1.3.2.2 Non-Organometallic ETL Compounds
Organic ETL compounds have high electron affinity aromatic heterocycles. For
example, in compound TAZ, 1, 2, 4- triazole can be synthesized from aniline and
hydrazine by a dehydration-condensation reaction in the presence of PCl3.116
The pyrimidine cycle has very good electron affinity. The conjugated compounds with
pyrimidine cycle can be used as ETL materials. They can be synthesized by Suzuki
coupling reaction with the constructed pyrimidine cycles117 or by using ring closing
reaction to form the pyrimidine cycles (Fig 1.15 ).118
O
NH
HN
O
NH2
N
N NPCl3
26
N
NIBr
R(HO)2B N
NBr R
Pd(PPh3)4, Na2CO3
Toluene, reflux
OC8H17
C8H17O
B(OH)2(HO)2B
Pd(PPh3)4, P(t-Bu)3,Na2CO3
Toluene, reflux
23
OC8H17
C8H17O
N
NR
N
NR
.
27
N
NN
NMe2N
Me2N
N
N
NH2
NH2
Pyridine
.
28
Fig 1.15 Pyrimidine units in ELT materials
The organic compounds with triazene cores also have good electron transporting
ability. These triazine compounds can be synthesized by imine and benzamidine ring-
closing reactions,119 lithium reagent and 2, 4, 6-trichlorotriazene substitution reactions
and CF3SO3H catalyzed trimerization reactions. 120 121
FN
NH2
NHN
N
NF
2
29
24
BrN
N NN
Cl
ClCl N N
N
NN
N
Et
Et
1. n-BuLi, THF, -400C
2.
Et
Et
Et
Et
Et Et
.
30
CNBr N N
N
N
N
N
N N
N
NN
N
N N
N
BrBr
Br
CF3SO3HNH
NN
CuSO4, K2CO3
31
Fig 1.16 Triazene units in ETL materials
Some special structure compounds (such as silole cycle compounds) have very good
properties as ETL materials. Silole cycle compounds have special orbital symmetry. The
σ*(Si)-π(C) action can lower LUMO energy level and is propitious for electron
injection.
Silole cycle compounds were synthesized by a reduction cyclization reaction of
dialkynylsilane derivatives first and then extended the molecular length by Pd catalyzed
coupling reaction. Intramolecular C-Si bond forming reaction was also used in silole
cycle compounds reduction cyclization reaction (Figure 1.17).
122,123
124
125
25
Triaryl boride compounds can also be used as ETL materials. Direct organometallic
substitution, such as addition reaction of aryllithium reagent and diaryl halogenoborate
was chosen for the synthesis.126,127
Fluorine atom has high electronegativity and can be used as substitution group of
aromatic conjugated compounds. These compounds can be synthesized by Ullmann
coupling reaction. They are effective ETL materials (Figure 1.18).128
Si
Me MeS
Me Me
ZnClClZn
N N
SMe Me
N N
NN
Br1. LiNaph(4 equiv.),
THF
2. [ZnCl2(t-men)](4 equiv.) Pd(PPh3)2Cl2
32
SiMe2(OEt) SiMe2(OEt)
(EtO)Me2Si (EtO)Me2Si
SiSi
Si Si
Me Me
Me Me
Me Me
Me Me
1. LiNaph(8 equiv), THF
2. I2 (8 equiv)
33
Fig 1.17 Silole units in ETL materials
S SSLiLi
B
S SSBB
F
34
26
F F
F F
F4
Br Br
F F
F F
F
F F
F F4
F F
F F
F Cu
.
35
Fig 1.18 Boride and per-fluorobenzene units in ETL materials
Oxidizing the sulphur atom in thiophene can change the electron rich properties of
thiophene to electron deficient. The conjugated compounds, which were constructed
from oxidizing part of thiophene by coupling reaction, can also be used as ETL
materials.129,130
The normal conjugated hydrocarbons have no electron transporting ability. But
cyclooctatetraene can be used as ETL material. It was synthesized by Ru catalyzed
cyclotetramerization reaction.131
9,9- Diaryl trifluorene compounds (TDAF) have been proved to have high efficiency
in electron transporting.132 Suzuki-coupling reaction was used in the synthesis route.
These pure hydrocarbons can be used as ETL materials in the OLED devices (Figure
1.19).133
S
C6H13 C6H13
O O
Bu3Sn
S
C6H13 C6H13
Br
O O
Br
Pd(AsPh3)4Toluene
.
36
27
(Ph3P)3Ru(CO)H2
Toluenen, Styrene
a
37
Ar Ar Ar ArAr Ar
BBO
OO
OAr Ar
Ar Ar
Br X
Pd(PPh3)4, P(t-Bu)3
Na2CO3, Toluene, reflux
38
Fig 1.19 Thiophenesulfone, cyclooctatetraene and diarylfluorene units in ETL materials
1.3.3 Blue light emitting materials
Blue light has shorter wavelength and higher energy and can be changed to green and
red light by energy transfer. High efficient blue light emitting materials play a very
important role in full color OLED display panel. Pure aromatic hydrocarbons such as
BTP have very good blue light emitting properties.134 BTP can be synthesized by Pd
catalyzed ring-opening dimerization reaction(Figure 1.20).135
The blue light emitting compounds with spirobifluorene backbones have higher
fluorescence quantum yield because of their rigid and co-planar structure. The synthesis
route started from constructing of spirobifluorene core. After halogenation reaction of the
spirobifluorene cores, the conjugated length of the molecules can be extended by
transition metal catalyzed coupling reaction.136 Suzuki coupling reactions were often used
in these reactions (Figure 1.20).137-139
28
O
HSiCl3
Pd(dba)2, Zn, Toluene .
39
.
40
.BBO
O O
O
Br
+
Pd(PPh3)4, P(t-Bu)3
Na2CO3, Toluene, reflux
.
41
O
O
OBB
O Pd(PPh3)4, P(t-Bu)3
Na2CO3, Toluene, reflux+
N
NBr t-Bu
N
N
N
Nt-But-Bu
42
29
Toluene, aliquat 336
Pd(PPh3)4, K2CO3
BO
O
+B
O
OBr .
43
Fig. 1.20 Spirobifluorene units in blue light emission materials
The great steric hindrance of spirobifluorene avoids intermolecular stacking. It can be
used as terminal group. Spirobifluorene140 and other special steric hindrance groups141,142
were introduced into the 9, 10-position of anthracene. The obtained blue light emitting
material has very good device properties (Figure 1.21).
+Br
(HO)2B B(OH)2
Pd(PPh3)4.
K2CO3, THF/H2O
44
30
O
O
Br Li OH
HO
Br
Br
NH
NN
Et2O,-780C
KI/NaHPO2
HOAc, reflux
Pd2(dba)3, P(t-Bu)3, NaO(t-Bu)
Br
Br
45
Fig. 1.21 Steric hindrance groups in blue light emission materials
The stilbene kind compounds such as DPVBi(46)143 have good blue light emitting
device efficiency. Their silicon substitution compounds also emit blue light. The key
synthesis reaction was hydrosilylation which formed C-Si bond.144,145
Compound XTPS (47) was found to have good blue light emission properties. Its
terminal groups were constructed by Diels-Alder reaction. Its C=C bonds were
constructed by Horner-Wadsworth-Emmons reaction (Figure 1.22).146
31
SiMe2HHMe2Si
OC4H9
C4H9O
H
RhCl(PPh3)3
SiSi
OC4H9
C4H9O
Me
Me
Me
Me
46
47
Fig. 1.22 Stilbene units in blue light emission materials
Some heterocycle conjugated compounds have good blue light emitting quantum
yields and can be used as the emitting layer in OLED device. Compound MeCl(49) wit
e C-N bonds then
llowed the BBr3 deprotection and cyclic condensation (Figure 1.23).
h
a coumarin backbone, was synthesized by Ullmann reaction to form th
fo
Ph3Si(PhTPAOXD)(compound 50) has a electron deficient 1, 3, 4-oxadiazole ring and
electron rich triarylamine groups.147 This makes it possible for the charge transfer in the
molecule. This dipolar molecule design keeps a balance in the electrons and holes
combination. The key step of the synthesis is the cyclization reaction of oxadiazole
(Figure 1.24)
32
O
Ph Ph
PhPh
CO2HPh Ph
PhPh
CO2H
Ph Ph
PhPh
1. LAH
2. CCl4, PPh3
3
P(OEt)2
O
N
CHO
PhBr
1. NaH
2.
3. P(OEt)
NPh Ph
Ph
Ph
48
MeO
NH2
Me
IN
OMe
N O O
Cu, K2CO3, 18-crown-6,1,2-dichlorobenzene
1. BBr3
2. Acetoacetic acid70% Sulphuric acid
49
Fig 1.23 Tetra-phenyl substituted stilbene and coumarin structure units in blue light emission materials
CH3Br COOHPh3Si
N
NHN N
NN
1. n-BuLi
3. KMnO4
1. SOCl2
2. Ph3SiCl
O
N NPh3Si
2.
.
50
Fig 1.24 Oxadiazole units in blue light emission materials
33
1
route.
.3.4 Green light emitting materials
Coumarin serial compounds have high green light emitting quantum yields. Many
derivatives were synthesized to improve the emitting efficiency. Compound 51 have
very good green light emitting efficiency because of the introduction of rigid julolidine
structure and four methyl groups’ steric hindrance.148 The construction of core cycle
structure in coumarin serial compounds was very important in the whole synthesis
149 150 In the synthesis of compound 52, coumarin ring was constructed first and
ine to obtain the heterocycle part (Figure 1.25). then reacted with 1, 2-phenyldiam
N OH
O
HN
SEtOO
N O
N
Spiperidine
O .
51
N N O ON O O
O
OEtH N2
H2N
HN
N
OHO
OEt
EtO OEtO
52
Fig 1.25 Coumarin units in green light emission materials
Many structures of organic chromophores can be learnt from nature simulation. For
example, the oxazolone part derived from green fluorescent protein aequorea was very
efficient in green light emission. 151
34
The compounds with pyrrole ring core structure can work as OLED green light
dopants.152 They can be synthesized by introducing pyrrole-thiophene rings first, then
introducing aldehyde and electron-withdrawing groups in the C=C bond coupling
reactions. N, N’-diethylquinacridone is also a good green dye in OLED devices (Figure
1.26).153,154
NO
O
NH
OOH
O
O
HNaOAc, acetic anhydride
.
53
NSS
OMe
NSS
OMe
CHO
NSS
OMe
S
Me
O
O
MeS
MeS S
O
MeO
1. n-BuLi, -780C
2. DMFn-BuLi, TMSCl,
0THF, -78 C
54
HO2C
PhHN
NHPh
N
NO
H O
H
N
NO
Et O
Et
CO2H
H3PO4
H2O
EtBr
55
Fig 1.26 Oxazolinone and pyrrole units in green light emission materials
35
Combining the high fluorescence quantum yield of anthracene and hole transporting
properties of triarylamine compounds, α-NPA is a good candidate of green light emission
materials.155 It can be synthesized by Pd catalyzed C-N bond coupling reaction. The same
synthetic methods can also be used in the synthesis of hole transporting new green light
emitting materials with dibenzochrysene part (Figure 1.27).96,156
Br Br N N
NH
Pd(OAc)2, P(t-Bu)3NaO(t-Bu), o-Xylene
.
56
O
NPh2Ph2N
O
Ph2N NPh2
Ph2N
NPh2
NPh2Ph2N
Ph2N NPh2
P(OEt)3 H
57
Fig 1.27 Diphenylamine units in green light emission materials
To keep a balance in electron-hole recombination, some special structure parts were
introduced into the chromophores. In a dipolar molecule with a carbazole core, its
emission efficiency was highly improved when oxadiazole cycle was introduced(Figure
1.28).157,158
36
NEt
Br
NEt
PhHN NHPh
PhN NHPhPd(dba)2, P(t-Bu)3NaO-(t-Bu), Toluene
O
N NBr
C4H9 C4H9
NEt
PhN PhNO
N N
C4H9 C4H9
Pd(dba)2, P(t-Bu)3NaO-(t-Bu), Toluene
58
NEt
Br
NEt
CNBrCN
NEt
NEt
CNN
CuCN
THF
NBS
DMF
NHP
Pd(dba)2, P(t-Bu)3NaO-(t-Bu), Toluene
h
.
59
Fig 1.28 Oxadiazole and nitrile units in green light emission materials
The synthesis method of dipolar molecule design can also be used in the other colors
light emitting materials. For the synthesis of compound 61,159 the key step is Cu
catalyzed Ullmann reaction. Thiophene ring was introduced by Suzuki reaction. Lithium
reagent was used to do the deprotonation. In the final, borane reagent was used to
t molecule (Figure 1.29). complete the addition reaction to obtain the targe
37
Me Me
I
MeMe
NH2 N
MeMe
Cu, K2CO3,18-Crown-6trimethyl benzene
1. NBS
2. Pd(PPh3)4,THF, K2CO3
S B(OH)2
.
B
F
Me
MeN
MeMe
SB
Me
MeN
MeMe
1. n-BuLi
2.
S
60
Fig 1.29 Bipolarity molecular design in green light emission materials
1.3.5 Red light emitting materials
In red light emitting materials design, the emitting light wavelength can be extended to
red light area by using intramolecular energy transfer. These Donor-Accepter (D-A) kind
molecules have very strong molecular dipole. The strong interaction of these pure
molecules as emitting layer materials often resulted in fluorescence quenching. Thus
these D-A kind molecules were often used as dopants in OLED devices. In these
materials, DCM(61)160,161 and DCJTB(63)162,163 can be obtained by condensation reaction
of amino benzaldehyde derivatives electron-donors and electron accepter parts. Changing
the electron accepters to be isophorone would avoid by-products forming and a series of
red light emitting materials with good properties can be synthesized (Figure 1.30).164-166
38
N
O
CNNC
61
.
N
CNNC
62
.
.
O
CNNCN
OH
HNN
O
NC CN
..
, CH3CN
63
.O
NC CN
N
NC CN
NC CN
Ac O2
NO
H
HN , CH3CN
64
OH
O
OH
O O
O
O
EtOAc
EtON
HOAc
HCl
NC
a
CN
Ac O2
O
NC CN
NO
HNO
NCCN
.
piperidine, CH3CN
65
Fig 1.30 Isophorone and chromene units in red light emission materials
39
In pure hydrocarbons, Polyacenes can be used as red light emitting dye dopant because
of their good molecular conjugation.167 In these compounds, 6, 13-diphenylpentacene
(DPP)(66) can be synthesized by addition reaction of Grignard reagents and quinone
compounds.168 Rubrene(67) can be synthesized by cyclization reaction of propargyl
chloride and quinoline (Figure 1.31).169,170 High fluorescence red light materials can also
be obtained by reaction of neutral red and naphthalic anhydride (Figure 1.32).171
O
O MgBr HO
OH
PhPh
KI
HOAC
66
Cl
Ph Ph
Quinoline
67
O
O
NEt
EtLi
NEtEt
NEt Et
NEtEt
NEt Et
HO
HO
SnCl2
68
40
Fig 1.31 Polyacene units in red light emission materials
N
N CH3
NH2NH3C
CH3
N
N CH3
NH3C
CH3
O OO
N
O
OQuinoline
.
69
Fig 1.32 Neutral red core in red light emission materials
In red light materials design, introducing the structure parts with electron-transporting
or hole transporting properties can balance the electrons and holes recombination
efficiency.
These materials pure thin films can be used directly as emitting layers in devices.172
Benzo- α – aceanthrylene derivatives, with properties of polycyclic aromatics and
triarylamine groups hole-transporting, can be used as pure emitting layer. The key
synthesis step was addition and dehydration reaction of anthroquinone. The final product
can be obtained by Pd catalyzed C-N bond coupling reaction and cyclization reaction in
the meantime.173
Arylamino fumaronitrile, with two CN groups in the C=C double bond and triaryl
amino group as electron-donor, is a good red light material. It can be obtained by
dimerization of phenylacetonitrile and Pd catalyzed reaction to introduce aromatic amine
groups (Figure 1.33).174
41
IMeO
HN
N
OMe OMe
N
CHO
Cu, K2CO3
1. POCl3, DMF
2. NaOH
MeOCNNC NC
NaOMeCN
OMe
70
Br
O
O
Cl
Br
Br
HO
OH
Cl Cl
Br
NH NN
Br Li KI
NaH2PO2HOAc
.
71
Pd(OAC) , P(t-Bu)2 3
Cs2CO3, Toluene
72
Fig 1.33 ETL and HTL structure units in red light emission materials
A series of single layer red light emitting materials were obtained by using maleimide
as electron-accepter structure parts and introducing aromatic amino groups as electron-
donors (Figure 1.34).175-178
42
Br
CN
HNO O
Br Br
NO O
Br Br
CH3
NH
1. I2, THF,NaOMe/MeOH
2. 3% HCl, THF
KO(t-Bu), CH3I,DMF
NCH3
O O
Pd(OAC)2, P(t-Bu)3NaO(t-Bu), Xylene
N N
73
NO O
Br Br
CH3N
CH3
NO OCH3
CH3
N N
1. MeMgCl
2.
.
74
.
NS
N
BrBrBu3Sn
NS
N
Br
N
S NBu3Sn
Pd(PPh3)2Cl2, DMF Pd(PPh3)2Cl2, DMF
N
S
NS
N
N
75
A new D-A kind materia
Fig 1.34 Maleimide and benzothiadiazole units in red light emission materials
l can also be used as pure single emitting layer. It combined
the high electron affinity of benzothiadiazole and electron rich property of thiophene and
43
triarylamine. The Pd catalyzed Stille reaction was the key step in synthesis (Figure
1.34).179
1.3.6 Hole Blocking materials
A charge carrier blocking layer was introduced in the device design for an effective
controlling of excitons combination area. Now hole blocking materials is common used
as blocking layer. To keep the holes effectively before the electron-transfer layer, hole
blocking materials should have lower HOMO energy level. High electron affinity groups
such as aromatic heterocycles or fluorinated organic conjugated compounds were often
used in hole blocking materials design. A good hole blocking material can have good
electron-transfer and electron-injection properties simultaneously. BCP180 is a common
hole blocking material. It was synthesized by addition reaction of quinoline and phenyl
propenyl ketone and H3ASO4 catalyzed cyclization dehydration reaction.181
1,3,4-oxadiazole is a high electron deficient heterocycle. It was introduced into
conjugated system to be electron-transfer material. An effective hole blocking material
can be obtained by connecting 1, 3, 4-oxadiazole with another electron-deficient structure
part such as pyridine (Figure 1.35).182
NNH2 O
N N
76
1. 85% H3PO4, 1200C
2. H3AsO4
.
44
N
O
OH
O
HO N
O
NHNH2
O
H2NHN
O1. MeOH/H2SO4 t-Bu
Cl
N
O
NHNH
O
HNHNO O
t-Bu t-Bu
N
O
N N
O
N Nt-Bu t-Bu
PDPyDP
POCl3
2. EtOH/N2H4 H2O Pyridine
77
Fig 1.35 BCP and Oxadiazole units in hole blocking materials
Dipyridine derivatives with coplanarity have good electron-transfer and hole blocking
properties.183 It can be synthesized by strong Friedel-Craft reaction of 4, 5-diazafluoren-
9-one and anisole derivatives.184,185
Conjugated compounds with shorter alkyl chains can also be used as good hole
blocking materials. For example, TFPB, its star-shaped structure can effectively limit the
whole molecule conjugation extension and lower the HOMO energy. Suzuki reaction was
the key step in the TFPB synthesis.186
Another synthesis design used σ bonds as blocking parts of molecular conjugation
extension. Si atom was used as the blocking part in DPSVB molecule to confine the
molecular conjugation length in the central conjugated cell.187 It can be synthesized by
Nickel catalyzed coupling reaction of thioacetal and silicon containing Grignard reaction
(Figure 1.36).188
45
N N N N
OMeO
N N
MeO OMe
KMnO4
KOH H2SO4, 650C.
78
I
II
B(OH)2
Pd(PPh3)4,THF, K2CO3
79
Me
S
SS
S
Si
Si
MeNiCl2(PP
Ph2MeCH2MgCl
h3)2
80
materials
1.4 Project objectives
Conjugated organic compounds play a primary role in the development of a new
generation of opt
Fig. 1.36 Diazofluorenone, star-shape fluorene and aryl silane units in hole blocking
ical and electronic materials. Our research focus on the synthesis of
ovel fluorene based polymers and oligomers. Novel structure units and novel synthesis
methodology play important roles in our research work.
n
46
Figure 1.37 Chapters work diagram
Figure 1.38 is the diagram of our four chapters work. In this diagram, Diaryl
ne is our key precursor. From this compound, we can easy to obtain
PPV compounds (Chapter 2). The novel fulvalenes polymers
dibromomethyl benze
the diaryl substituted
(Chapter 3) were introduced to explore the bistricyclic aromatic units’ effect in polymer
properties. The tetra-aryl substituted cyclophane compounds (Chapter 4) can also be
obtained by using our key precursor. Hexaarylbenzene compounds were synthesized to
47
study their properties and relations with the structure. The more details of the work will
be explained in following paragraphs.
Polymer light-emitting devices (PLEDs) are the most intensely investigated area for
the application of PPV derivatives. PPV provides excellent hole-transporting layers189 in
PLEDs in addition to be the active emissive layer. With precisely chemical modifications
and device engineering, PPVs give colors which cover the entire visible spectrum of
colors with good efficiencies under a bias of only a few volts. In addition, the excellent
film-forming properties of PPVs suggest that a large area display can be fabricated from
these polymer materials.
PPV compounds have a good planarity due to their conjugated alkene skeleton. This
planarity is important for charge separating and transfer. But aggregation was also caused
by the good planarity. This aggregation will deduce the quantum yield and solubility of
polymers. In our work, we hope to introduce huge steric hindrance chromophores as side
chains into the PPV polymers. These side chains will combine their own properties
together with the PPV main chain and adjust the properties (such as HOMO, LUMO
ic hindrance caused by these side chains can be a
through the interring double bond and capable of generating two separate aromatic
energy level) of polymers. The ster
favorite factor to decrease the aggregation and increase the photoluminescence efficiency
of polymers. In the work of PPV derivatives polymers synthesis, two chromophore side
chains PPV compounds were designed. By our knowledge, this is the first time to
synthesize these di-chromophore side chains PPV compounds. We hope to explore these
novel derivatives properties and applications.
Fulvalenes are molecules with two unsaturated ring systems showing cross conjugation
48
moieties. By our knowledge, no report has been made on tetrabenzofulvalene’s usage in
materials. In order to investigate the effect of bistricyclic aromatic units on the polymer
f [2, 2] parcyclophane190 was used in almost all of the works to
macromolecules that consist of linear
backbone, two novel tetrabenzofulvalene units containing polymers were designed. We
hope to explore how the Tetrabenzo[5.5]fulvalene make an effect on whole polymer
properties and find the potential application of these polymers.
Cyclophane, in which two benzene rings are close to each other and cofacial, is
attractive in its structure, reactivity and physical properties. Cyclophanes have optically,
electrically, and topologically intriguing features.
Direct bromination o
obtain the desired cyclophane bromides from which functional groups can be attached on.
The yield of this method is very low and has almost no possibility to have different
substituents on one cyclophane core. In our work, novel tetra-substituted
[2.2]paracyclophanes with different chromophores were designed. We hope to construct
cyclophane core by using coupling reaction. By this method, we can attach the wanted
functional groups on the two aromatic benzene rings first. Then we use two same or
different substituted benzene rings to form the cyclophane core. This gives us wider
choice to introduce different functional groups on the cyclophane cores. This freely
modification makes the synthesis route very useful to obtain different [2.2]
paracyclophanes derivatives which can be used in different applications areas such as
asymmetric reaction, OLED and NLO materials.
Star-shaped oligomers are branched
molecular arms joined together by a central core191. Star-shaped oligomers are unique in
the sense that they combine the properties of the arms with that of the central core (which
49
can have one to three dimensional characters) and this will bring new interesting
optoelectronic and morphological properties to the system. Recently, hexaarylbenzene
have attracted immerse interest in the materials community; aryl “arms” such as
azulene192, pyrene193 and ferrocene194 have been attached and these systems shows more
superior properties than their trisubstituted star-shaped analogue. In our work, we try to
ficiency and their ease of
synthesize high steric hindrance hexafluorenylated benzene. We thus decide to tap on
the potential of such “double” star-shaped system, using “fluorenyl” units as the arms as
fluorenes are known for their high photoluminescence ef
chemical transformation. We hope to test the structure and properties of resultant system.
In addition, the nature of the side chains at the 9th position of fluorene will be investigated
to see if its length affects the formation of hexafluorenyl benzene.
50
Reference
1. Shirakaw, H.; Louis, E. J.; Macdiarmid, A. G.; Chiang, C. K.; Heeger, A. J. J.
Chem. Soc., Chem. Commun. 1977, 578.
2. Skotheim, T. A. Handbook of Conducting polymers, Marcel dekker, New York,
1986.
3. Miller, J. S.; Epstein, A. J. Angew. Chem. Int. Ed. 1994, 33, 385.
4. Pattil, A. O.; Heeger, A. J.; Wudl, F. Chem. Rev. 1988, 88, 183.
5. Feast, W. J.; Tsibouklis, J.; Pouwer, K. L.; Groenendaal, L.; Meijer, E. W.
Polymer 1996, 37, 5017.
6. Salafsky, J. S.; Laberhuizen, W. H.; Schropp, R. E. I. Chem. Phys. Lett. 1998, 290,
297.
. Bradley, D. D. C. Chem. Ber. 1991, 21, 719.
. Bradley, D. D. C.; Brown, A. R.; Burn, P. L.; Burroughes, J. H.; Friend, R. H.;
Greeham, N. C.; Gymer, R. W.; Holmes, A. B.; Kraft, A. M.; Marks, R. N.
Photochemistry and Polymeric Systems, Royal Society of Chemistry, "Conjugated
Polymer Electro-optic devices", 1993, 120.
. Greeham, N. C.; Friend, R. H. Solid State Phys. 1995, 49.
0. Roth, S.; Bleier, H. Adv. Phys. 1987, 36, 285.
1. Heeger, A. J.; Kivelson, S.; Schrieüer, J. R.; Su, W. P. Rev. Mod. Phys. 1988, 60,
781.
2. Chein, J. C. W. Polyacetylene: Chemistry, Physics and materials Science,
Academic, New York, 1984.
7
8
9
1
1
1
51
13. Kraft, A.; Grimsdale, A. B. Angew. Chem. Int. Ed. 1998, 37, 403.
14. Novak, P.; Müllen, K.; Santhanam, K. S. V.; Hass, O. Chem. Rev. 1997, 97, 207.
Nature 1990, 347, 539.
17. May, Physics world 1995, 52.
, 35.
21. Physics of Organic Light-emitting Diodes Ph. D.
22. , Y.; Pei, Q.; Heeger, A. J. J. Appl. Phys. 1996, 79, 934.
. Chem. 1984, 49, 3382.
25.
26. 183.
Analysis, 4th edition,
d, R. H.; Greeham, N. C.; Gymer, R. W.; Hallicay, D. A.; Jackson, R. W.;
15. Burroughes, J. H.; Bradley, D. D. C.; Brown, A. R.; Marks, R. N.; Mackay, K.;
Friend, R. H.; Burn, P. L.; Holmes, A. B.
16. Bunz, U. H. F. Chem. Rev. 2000, 100, 1605.
P.
18. Friend, R. H.; Burroughes, J. H.; Shimoda, T. Physics world 1999
19. Harrison, W. A. Solid State Theory, Dover, New York, 1979.
20. Kanatzldis, M. G. C&E News 1990, 36.
Shaheen, S. E. Devices
dissertation, University of Arizona, 1999.
Yang
23. Wudl, F.; Kobayashi, M.; Heeger, A. J. J. Org
24. Colaneri, N.; kobayashi, M.; Heeger, A. J.; Wudl, F. Synth. Met. 1986, 14, 45.
Halls, J. J. M.; Walsh, C. A.; Greeham, N. C.; Marseglia, E. A.; Friend, R. H.;
Moratti, S. C.; Holmes, A. B. Nature 1995, 376, 498.
Yu, G.; Heeger, A. J. Synth. Met. 1997, 85, 1
27. Skoog, D. A.; Leary, J. J. Principles of Instrumental
Saunders Colleage Publishing, 1992
28. Holmes, A. B.; Bradley, D. D. C.; Brown, A. R.; Burn, P. L.; Burroughes, J. H.;
Frien
kraft, A.; Martens, J. H. F.; Pichler, K.; Samuel, I. D. W. Synth. Met. 1993, 55,
4031.
52
29. Brown, A. R.; Greeham, N. C.; Burroughes, J. H.; Bradley, D. D. C.; Friend, R.
31. Holmes, A. B.;
0.
liday, D. A.; Bradley, D. D. C.; Friend, R. H.;
oetti, H.; Robin, P.
cademic Published, 1996, 313.
. H. Chem. Phys. Lett. 1995, 241, 89.
73.
C.;
38. alvin, M. E.; Miller, T. M.
41.
42. , L. D.; Porter, S. J. Synth. Met. 1989, 28, C761.
H.; Burn, P. L.; kraft, A.; Holmes, A. B. Chem. Phys. Lett. 1999, 46, 200.
30. Salbeck, J. Ber. Bunsenges. Phys. Chem. 1996, 100, 1667.
Colaneri, N. F.; Bradley, D. D. C.; Friend, R. H.; Burn, P. L.;
Spangler, C. W. Phys. Rev. B, 1990, 42, 1167
32. Woo, H. S.; Graham, S. C.; Hal
Burn, P. L.; Holmes, A. B. Phys. Rev. B, 1992, 46, 7379.
33. Dubois, J. C.; Lebarny, P.; Bouche, C. M.; Berdague, P.; Fac
Photoactive Organic Materials, Kluwer A
34. Greeham, N. C.; Samuel, I. D. W.; Hayes, G. R.; Philips, R. T.; Kessener, Y. A. R.
R.; Moratti, S. C.; Holmes, A. B.; Friend, R
35. Jenekhe, S. A.; Osaheni, J. A. Science 1994, 265, 765.
36. Samuel, I. D. W.; Rumbles, G.; Collison, C. J. Phys. Rev. B 1995, 52, 5
37. Samuel, I. D. W.; Rumbles, G.; Collison, C. J.; Friend, R. H.; Moratti, S.
Holmes, A. B. Synth. Met. 1997, 84, 497.
Yan, M.; Rothberg, L. J.; Papadimitrakopoulos, F.; G
Phys. Rev. Lett. 1994, 73, 744.
39. Wudl, F.; Allemand, P. M.; Srdanov, G.; Ni, Z.; Mcbranch, D. ACS Symp. Serv.
1991, 455, 683.
40. Potember, R. S.; Hoffmann, R. C.; Hu, H., S.; Cocchiaro, J. E.; Viands, C. V.;
Murphy, R. A.; Poehler, T. O. Polymer 1987, 28, 574.
Bond, S. F.; Howie, A.; Friend, R., H. Sur. Sci 1995, 333, 196.
Couves
53
43. Zinger, B.; Miller, L. L. J. Am. Chem. Soc. 1984, 106, 6861.
Umana, M.; Weller, J. Anal. Chem. 1986, 58, 2979. 44.
37, 224.
47.
49. 1985, 89, 1441.
52. .
Chem.
54. hem. Commun. 1983, 13, 809.
56. 7.
58. ao, Y.; Treacy, G. M.; Klavetter, F.; Colaneri, N.; Heeger, A. J.
59. nce 1995, 269, 1086.
. Soc. 1996, 118,
45. Barlett, P. N.; Whitaker, R. G. J. Electroanal. Chem. 1987,
46. Caglar, P.; Wnek, G. E. J. Macromol. Sci. Pure. Appl. Chem. 1995, A32, 349.
Jung, K. S.; Wilson, G. S. Anal. Chem. 1996, 68, 591.
48. Swager, T. M. Acc. Chem. Res. 1998, 31, 201.
Paul, E. W.; Ricco, A. J.; Wrighton, M. S. J. Phys. Chem.
50. Okoniewski, M. Modifizerung der Synthesefasern zur Erzielung von leitfahigen;
Melliand textiber: Anderen Eigenschaften, 1990; Vol. 71, 94.
51. Kuhn, W.; Hargitay, B.; Katchalsky, A.; Eisenberg, H. Nature 1950, 165, 514.
Angelopoulos, M.; Shaw, J. M.; Kaplan, R. D.; Perreault, S. J. Vac. Sci. Technol
B. 1989, 7, 1519.
53. Clarke, T. C.; Krounbi, M. T.; Lee, V. Y.; Street, G. B. J. Chem. Soc.,
Commun. 1981, 8, 384.
Pitchumani, S.; Willig, F. J. Chem. Soc., C
55. Colaneri, N. F.; Shacklette, L. W. IEEE trans. Instrum. Meas. 1992, IM-41, 291.
T., T. Synth. Met. 1991, 41, 177
57. Joo, J.; Epstein, A. J. Appl. Phys. Lett. 1994, 65, 2278.
Gustafsson, G.; C
Nature 1992, 357, 1789.
Pei, Q.; Yu, G.; Zhang, C.; Yang, Y.; Heeger, A. J. Scie
60. Pei, Q.; Yang, Y.; Yu, G.; Zhang, C.; Heeger, A. J. J. Am. Chem
3922.
54
61. Yu, G.; Heeger, A. J. J. Appl. Phys. 1995, 78, 4510.
62. Hals, J. J. M.; Walsh, C. A.; Marseglia, E. A.; Friend, R., H.; Moratti, S. C.;
,
ture 1998, 335, 137.
4.
67. Katz, H. E. Science
69. Mater. 1998, 10, 365.
.
artz, B. J.; Heeger, A. J. Acc. Chem. Res. 1997,
1997, 85, 1295.
Holmes, A. B. Nature 1995, 396, 498.
63. Yu, G.; Cao, Y.; Hummelen, J. C.; Wudl, F.; Heeger, A. J. Science 1995, 270
1789.
64. Burroghes, J. H.; Jones, C. A.; Friend, R., H. Na
65. Garnier, F.; Hajlaoui, R.; Yasser, A.; Srivastava, P. Science 1994, 265, 168
66. Brown, A. R.; Pomp, A.; Hart, C. M.; de Leeuw, D. M. Science 1995, 270, 972.
Torsi, L.; Dodabalapur, A.; Rothberg, L. J.; Fung, A. W. P.;
1996, 272, 1462.
68. Sirringhaus, H.; Tessler, N.; Friend, R., H. Science 1998, 280, 1741.
Horowitz, G. Adv.
70. Drury, C. J.; Mutsaers, C. M. J.; Hart, C. M.; Matters, M.; de Leeuw, D. M. Appl.
Phys. Lett. 1998, 73, 108
71. Yang, Y.; Heeger, A. J. Nature 1994, 372, 344.
72. Yu, G.; Pakbaz, K.; Heeger, A. J. J. Electron. Mater. 1994, 23, 925.
73. Hide, F.; Diaz-Garcia, M. A.; Schw
30, 430.
74. Halvorson, C.; Hays, A.; Kraabel, B.; Wu, R.; Wudl, F.; Heeger, A. J. Science
1992, 265, 1215.
75. Halger, T. W.; Heeger, A. J. Phys. Rev. B 1994, 49, 7313.
76. Reynolds, J. R.; Kumar, A.; Reddinger, J. L.; Sankaran, B.; Sapp, S. A.; Sotzing,
G. A. Synth. Met.
55
77. Yu, G.; Wang, J.; Mcelvain, J.; Heeger, A. J. Adv. Mater. 1998, 10, 1431.
12,
83. eisel, A.; Miteva, T.; Neher, D.; Forster, M.; Oda, M.; Lieser,
omol. Symp.
ical Industry Press Beijing, 2005; p. 313.
hardt, B. A. J. Org. Chem. 2000,
87. .; Xie, S.; Popovic, Z. D. Synth. Met. 2000, 111, 421.
89. pars, A.; Buchwald, S. L. Org. Lett. 2002, 4, 581.
92. ganomet. Chem. 1999, 576, 125.
78. Yu, G.; Cao, J.; Hummelen, J. C.; Wudl, F.; Heeger, A. J. Science 1995, 270,
1789.
79. Fukuda, M.; Sawada, K.; Yoshino, K. J. Polym. Sci. A: Polym. Chem. 1993, 31,
2465.
80. Pei, Q. B.; Yang, Y. J. Am. Chem. Soc. 1996, 118, 7416.
81. Bernius, M. T.; Inbasekaran, M.; OBrien, J.; Wu, W. S. Adv. Mater. 2000,
1737.
82. Ranger, M.; Leclerc, M. Macromolecules 1997, 30, 7686.
Nothofer, H. G.; M
G.; Sainova, D.; Yasuda, A.; Lupo, D.; Knoll, W.; Scherf, U. Macr
2000, 154, 139.
84. Wong, K., T.; Leung, M., K.; Luh, T. Y. In Progress of Advanced Organic
Synthesis Chemistry; Chem
85. Belfield, K. D.; Schafer, K. J.; Mourad, W.; Rein
65, 4475.
86. Goodbrand, H. B.; Hu, N. X. J. Org. Chem. 1999, 64, 670.
Hu, N. X
88. Antilla, J. C.; Klapars, A.; Buchwald, S. L. J. Am. Chem. Soc. 2002, 124, 11684.
Kwong, F. Y.; kla
90. Hartwig, J. F. Acc. Chem. Res. 1998, 31, 852.
91. Hartwig, J. F. Synlett 1997, 329.
Yang, B. H.; Buchwald, S. L. J. Or
56
93. Buchwald, S. L. Acc. Chem. Res. 1998, 31, 805.
94. Yamamoto, T.; Nishiyama, M.; Koie, Y. Tetrahedron Lett. 1998, 39, 2367.
Salbec95. k, J.; Weissortel, F.; Yu, N.; Bauer, J. B. Synth. Met. 1997, 91, 209.
Lett. 2000, 29, 192.
99. K. T.; Hung, T. S.; Kao, S. C.; Chou, C. H.; Su, Y. O. Chem. Commun.
101.
104. mae, I.; Noma, N.; Shirota, Y. Adv. Mater. 1997, 9, 239.
. 1999, 9, 2177.
; Müllen, K. Adv.
e, C. S.; Lee,
. L.; Zhang, L. Z.; Luh, T. Y. Appl. Phys. Lett.
96. Kimura, M.; Inoue, S. I.; Shimada, K.; Tokito, S.; Noda, K.; Taga, Y.; Sawaki, Y.
Chem.
97. Shirota, Y. J. Chem. Mater. 2000, 10, 1.
98. Shirota, Y.; Kobata, T.; Noma, N. Chem. Lett. 1989, 7, 1145.
Wong,
2001, 1682.
100. Thomas, K. R. J.; Lin, J. T.; Tao, Y. T.; Ko, C. W. Adv. Mater. 2000, 12, 1949.
Thomas, K. R. J.; Lin, J. T.; Tao, Y. T.; ko, C. W. J. Am. Chem. Soc. 2001, 123,
9404.
102. Tokito, S.; Iijima, T.; Suzuri, Y.; Kita, H.; Tsuzuki, T.; Sato, F. Appl. Phys. Lett.
2003, 83, 569.
103. Wu, I. Y.; Lin, J. T.; Tao, Y. T.; Balasubramaniam, E. Adv. Mater. 2000, 12, 668.
Noda, T.; I
105. Noda, T.; Ogawa, H.; Noma, N.; Shirota, Y. J. Mater. Chem
106. Ego, C.; Grimsdale, A. C.; Uckert, F.; Yu, G.; Srdanov, G.
Mater. 2002, 14, 809.
107. Mi, B. X.; Wang, P. F.; Liu, M. W.; Kwong, H. L.; Wong, N. B.; Le
C. T. Chem. Mater. 2003, 15, 3148.
108. Wu, C. C.; Hung, W. Y.; Liu, T
2003, 93, 5465.
57
109. Zhang, L. Z.; Chen, C. W.; Lee, C. F.; Wu, C. C.; Luh, T. Y. Chem. Commun.
111. r. Chem. 2003, 13, 479.
eon, D. H.; Cho, S. D.; Lee, S. G.; Yoon,
114. .; Wong, K. T.; Chou, P. T.; Cheng, Y. M. Chem. Commun. 2002,
116. S.; Chen, S. A. Adv. Mater. 2004, 16, 744.
rg. Lett. 2002, 4, 513.
ter. 1998, 10,
, 118, 11974.
2002, 2336.
110. Dorosenko, A. O.; Posokhov, E. A.; Verezubova, A. A.; Ptyagina, L. M. J. Phys.
Org. Chem. 2000, 13, 253.
Cha, S. W.; Jin, J. I. J. Mate
112. Park, Y. D.; Kim, J. J.; Chung, H. A.; Kw
Y. J. Synthesis 2003, 4, 546.
113. Huisgen, R.; Sauer, J.; Sturm, H. J. Angew. Chem. 1958, 70, 272.
Chien, Y. Y
2874.
115. Tanaka, H.; Tokito, S.; Taga, Y.; Okada, A. J. Mater. Chem. 1998, 8, 1999.
Yu, L.
117. Wong, K. T.; Hung, T. S.; Lin, Y.; Wu, C. C.; Lee, G. H.; Peng, S. M.; Chou, C.
H.; Su, Y. O. O
118. Gammper, P.; Mair, H. J.; Polborn, K. Synthesis 1997, 696.
119. Fink, R.; Heischkel, Y.; Thelakkat, M.; Schmidt, H. W. Chem. Ma
3620.
120. Wortmann, R.; Glania, C.; kraemer, P.; Matschiner, R.; Wolff, J. J. Chem. Euro. J.
1997, 3, 1765.
121. Peng, J.; Tao, Y.; Freiberg, S.; Yang, X. P.; D'Iorio, M.; Wang, S. J. Mater. Chem.
2002, 12, 206.
122. Tamao, K.; Uchida, M.; Izumizawa, T.; Furukawa, K.; Yamaguchi, S. J. Am.
Chem. Soc. 1996
58
123. Murata, H.; Kafafi, Z. H. Appl. Phys. Lett. 2002, 80, 189.
Yamaguchi, 124. S.; Endo, T.; Uchida, M.; Izumizawa, T.; Furukawa, K.; Tamao, K.
125. ao, K. J. Am. Chem. Soc. 2003, 125, 13662.
714.
a, H.; Mori, T.;
129. ella, G.; Favaretto, L.; Sotgiu, G.; Zambianchi, M.; Bongini, A.; Arbizzani,
2000,
3, 5479.
mpson, M. E. J. Am.
132. . C.; Liu, T. L.; Hung, W. Y.; Lin, Y. T.; Wong, K. T.; Chen, R. T.; Chen,
133. hien, Y. Y.; Chen, R. T.; Wang, C. F.; Lin, Y. T.; Chiang, H. H.;
2, 124, 11576.
135. , C. H. Org. Lett. 2001, 3, 811.
Chem. Euro. J. 2000, 6, 1683.
Yamaguchi, S.; Xu, C.; Tam
126. Noda, T.; Shirota, Y. J. Am. Chem. Soc. 1998, 120, 9
127. Branger, C.; Lequan, M.; Lequan, R. M.; Barzoukas, M.; Fort, A. J. Mater. Chem.
1996, 6, 555.
128. Heidenhain, S. B.; Sakamoto, Y.; Suzuki, T.; Miura, A.; Fujikaw
Tokito, S.; Taga, Y. J. Am. Chem. Soc. 2000, 122, 10240.
Barbar
C.; Mastragostino, M.; Anni, M.; Gigli, G.; Cingolani, R. J. Am. Chem. Soc.
122, 11971.
130. Barbarella, G.; Favaretto, L.; Sotgiu, G.; Zambianchi, M.; Antolini, L.; Pudova,
O.; Bongini, A. J. Org. Chem. 1998, 6
131. Lu, P.; Hong, H.; Cai, G.; Djurovich, P.; Weber, W. P.; Tho
Chem. Soc. 2000, 122, 7480.
Wu, C
Y. M.; Chien, Y. Y. J. Am. Chem. Soc. 2003, 125, 3710.
Wong, K. T.; C
Hsieh, P. Y.; Wu, C. C.; Chou, C. H.; Su, Y. O.; Lee, G. H.; Peng, S. M. J. Am.
Chem. Soc. 200
134. Shih, H. T.; Lin, C. H.; Shih, H. H.; Cheng, C. H. Adv. Mater. 2002, 14, 1409.
Shih, H. T.; Shih, H. H.; Cheng
59
136. Wu, R.; Schumm, J. S.; Pearson, D. L.; Tour, J. M. J. Org. Chem. 1996, 61, 6909.
138. H. H. Appl. Phys. Lett. 2002, 81, 577.
1690.
142. ang, T. H.; Lin, J. T.; Tao, Y. T.; Chuen, C. H. Chem. Mater. 2002,
143. Kusumoto, T. Proceed
144.
145. Chien, K. M.; Wong, K. T. J. Am. Chem. Soc. 1997, 119, 11321.
147. r. 2001, 13, 1637.
149. , J.; Klubek, K. P. US Patent No. 6020078 2000.
, 15, 2305.
152. naka, S.; Fukuda, T.; Akazome, M.; Ogura, K.
0.
137. Spehr, T.; Pudzich, R.; Fuhrmann, T.; Salbeck, J. Org. Elec. 2003, 4, 61.
Wu, C. C.; Lin, Y. T.; Chiang,
139. Shen, W. J.; Dodda, R.; Wu, C. C. Chem. Mater. 2004, 16, 930.
140. Kim, Y. H.; Shin, D. C.; Kim, S. H. Adv. Mater. 2001, 13,
141. Shi, J.; Tang, C. W. Appl. Phys. Lett. 2002, 80, 3201.
Danel, K.; Hu
14, 3860.
Tokailin, H.; Matsuura, M.; Higashi, H.; Hosokawa, C.;
SPIE. 1993, 1990, 38.
Gao, Z.; Lee, C. S.; Bello, I. Appl. Phys. Lett. 1999, 74, 865.
Chen, R. M.;
146. Chen, C. T.; Chiang, C. L.; Lin, Y. C. Org. Lett. 2003, 5, 1261.
Chan, L. H.; Yeh, H. C.; Chen, C. T. Adv. Mate
148. Chen, C. H.; Tang, C. W. Appl. Phys. Lett. 2001, 79, 3711.
Chen, C. H.; Tang, C. W.; Shi
150. Swason, S. A.; Wallraff, G. M.; Chen, J. P.; Zhang, W.; Bozano, L. D.; Carter, K.
R.; Salem, J. R.; Villa, R.; Scott, J. C. Chem. Mater. 2003
151. You, Y.; He, Y.; Burrows, P. E.; Forrest, S. R.; Petasis, N. A.; Thompson, M. E.
Adv. Mater. 2002, 16, 1678.
Yanai, H.; Yoshizawa, D.; Ta
Chem. Lett. 2000, 29, 238.
153. Stengel-Rutkowski, B.; Boehmer, M. Euro. Coat. J. 2002, 11, 4
60
154. Liu, P.; Chang, C. P.; Tian, H. Proceed SPIE. 2002, 4464, 299.
155. Yu, M. X.; Duan, J. P.; Lin, C. H.; Cheng, C. H.; Tao, Y. T. Chem. Mater. 2002,
ada, K.; Sawaki,
. H. Chem. Mater. 2002, 14,
158. mas, K. P.; Lin, J. T.; Tao, Y. T.; Chuen, C. H. Adv. Funct. Mater.
159. M.; Noda, K.; Okumoto, K.; Ohara, T. J. Am. Chem. Soc.
65, 3610.
. T. J. Phys. D:
o.
164. ; Lee, C. S.;
165. be, H.; Zhang, G. J.; Wade, T.; Jiang, M. H. Appl.
166. in, X. Q. Chem. Mater. 2001, 13, 1565.
, 2378.
14, 3958.
156. Tokito, S.; Noda, K.; Fujikawa, H.; Taga, Y.; Kimura, M.; Shim
Y. Appl. Phys. Lett. 2000, 77, 160.
157. Justin Thomas, K. P.; Lin, J. T.; Tao, Y. T.; Chuen, C
3852.
Justin Tho
2004, 14, 387.
Shirota, Y.; Kinoshita,
2000, 112, 11021.
160. Lemke, R. Synthesis 1974, 359.
161. Tang, C. W.; Van-Slyke, S. A.; Chen, C. H. J. Appl. Phys. 1989,
162. Chen, B.; Lin, X.; Cheng, L.; Lee, C. S.; Gambling, W. A.; Lee, S
Apply. Phys. 2001, 34, 30.
163. Lee, S. T.; Hung, L. S.; Lee, C. S.; Lin, X. Q.; Zhang, X. H. US Patent N
2003099861.
Li, J.; Liu, D.; Hong, Z.; Tong, S.; Wang, P.; Ma, C.; Lengyel, O.
Kwong, H. L.; Lee, S. Chem. Mater. 2003, 15, 1486.
Tao, X. T.; Miyata, S.; Sasa
Phys. Lett. 2001, 78, 279.
Zhang, X. H.; Chen, B. J.; L
167. Picciolo, L. C.; Murata, H.; Kafafi, Z. H. Appl. Phys. Lett. 2001, 78
61
168. Allen, C. F. H.; Bell, A. J. Am. Chem. Soc. 1942, 64, 1253.
169. Bowen, E. J.; Steadman, F. J. Chem. Soc. 1934, 1098.
Odom, S. A170. .; Parkin, S. R.; Anthonyl, J. E. Org. Lett. 2003, 5, 4245.
173. , T. H.; Lin, J. T.; Tao, Y. T.; Chuen, C. H. Chem. Mater. 2003, 15, 4585.
175. , H. C.; Chan, L. H.; Chen, C. T. Adv. Mater. 2002, 14, 1072.
nneroski, L. Synthesis 1995, 1511.
8, 44,
179. J. T.; Velusamy, M.; Tao, Y. T.; Chuen, C. H. Adv.
180. ; Lamansky, S.; Burrows, P. E.; Thompson, M. E.; Forrest, S. R.
181. 9.
E.; Howark, J. A. K. Chem. Mater. 2001, 13, 1167.
.; Okada, H.;
171. Wang, P.; Xie, Z.; Tong, S.; Wong, O.; Lee, C. S.; Wong, N.; Hung, L.; Lee, S.
Chem. Mater. 2003, 15, 1913.
172. Kim, D. U.; Paik, S. H.; Kim, S. H.; Tsutsui, T. Synth. Met. 2001, 123, 43.
Huang
174. Yeh, H. C.; Yeh, S. J.; Chen, C. T. Chem. Commun. 2003, 2632.
Wu, W. C.; Yeh
176. Chiu, C. W.; Chow, T. J.; Chuen, C. H.; Lin, H. M.; Tao, Y. T.; . Chem. Mater.
2003, 15, 4527.
177. Faul, M. M.; Sullivan, K. A.; Wi
178. Brenner, M.; Rexhausen, H.; Steffan, B.; Steglish, W. Tetrahedron 198
2887.
Justin Thomas, K. P.; Lin,
Funct. Mater. 2004, 14, 83.
Baldo, M., A.
Appl. Phys. Lett. 1999, 75, 4.
Case, F. H.; Brennan, J. A. J. Org. Chem. 1954, 19, 91
182. Wang, C.; Jung, G. Y.; Hua, Y.; Pearson, C.; Bryce, M. R.; Petty, M. C.;
Batsanov, A. S.; Goeta, A.
183. Ono, K.; Yanase, T.; Ohkita, M.; Saito, K.; Matsushita, Y.; Naka, S
Onnagawa, H. Chem. Lett. 2004, 33, 276.
62
184. Yamada, M.; Sun, Y.; Suda, Y.; Nakaya, T. Chem. Lett. 1998.
Am. Chem. Soc. 1984, 106,
187. . T. Appl. Phys. Lett. 2001, 79, 3023.
.
1, 2793.
H.; Ohta, K.;
193. , D.; Lambert, C. Organic Letters 2006, 8, 5037-5040.
185. Henderson, L. J.; Fronczek, J., F. R.; Cherry, W. R. J.
5876.
186. Okumoto, K.; Shirota, Y. Chem. Mater. 2003, 15, 699.
Wu, C. C.; Chen, C. W.; Lin, Y
188. Luh, T. Y.; Basu, S.; Chen, R. M. Curr. Sci 2000, 78, 1352.
189. Brown, A. R.; Bradley, D. D. C.; Burroughes, J. H.; Friend, R. H.; Greeham, N
C.; Burn, P. L.; Holmes, A. B.; Kraft, A. Appl. Phys. Lett. 1992, 6
190. Bazan, G. C. J. Org. Chem. 2007, 72, 8615.
191. Hadjichristidis, N.; Pitsikalis, M.; Pispas, S.; Iatrou, H. Chem. Rev. 2001, 101,
3747.
192. Ito, S.; Ando, M.; Nomura, A.; Morita, N.; Kabuto, C.; Mukai,
Kawakami, J.; Yoshizawa, A.; Tajiri, A. J. Org. Chem. 2005, 70, 3939-3949.
Rausch
194. Chebny, V. J.; Dhar, D.; Lindeman, S. V.; Rathore, R. Organic Letters 2006, 8,
5041-5044.
63
Chapter Two
Synthesis and Characterization of Chromophore Side Chains
during investigations
cheape er. Its
m (2.4 eV) are in the yellow-green
synthesis of PPV directly from a monomer produces an insoluble material, which cannot
yields By
to four categories:
metath zation.
.1.1 Main synthesis routes of PPV compounds
.1.1.1 Sulfonium precursor route
The precursor approach relies on the pre of a soluble precursor polymer that
can be cast into thin films and then be transformed into the final conjugated polymer
films through solid state thermo- or photo-conversion. The sulfonium precursor
route(SPR) to PPV was introduced by Wessling and Zimmerman (Figure 2.1).3,4 It was
PPV Derivatives
2.1 Introduction
Electroluminescence in conjugated polymers was first discovered
into the electrical properties of poly(1,4-phenylene vinylene) (PPV),1 the simplest and
st poly(arylene vinylene). PPV is a bright yellow, fluorescent polym
emission maxima at 551 nm (2.25 eV) and 520 n
region of the visible spectrum. The polymer is insoluble, intractable, and infusible. Any
be easily processed. Solution processing by spincoating is particularly desirable as it
high quality transparent thin films for the production of polymer EL devices.2
now, the various synthetic routes to PPVs can be roughly divided in
precursor approach, side chain derivatization, polycondensation and ring-opening
esis polymeri
2
2
paration
64
then subsequently modified and op ps.5-7 As shown in Figure 2.1, it
involved the polym
presence of a base in water or methanol to give the corresponding sulfonium precursor
polymer. The principle has been of PPV-related copolymers.
timized by other grou
erization of p-xylene bis(tetrahydrothiophene chloride) in the
applied to a whole range
CH2ClClH2CS
SCl
Clterahydrothiophene
MeOH, 650C
1. NaOH, MeOH/H O2
2. neutralization(HCl)
3. dialysis(water)
1 2
S
SCl
OMe
n
Cl
n
n
MeOH, 500C
2200C, HCl(g)/Ar, 22h
180-3000C, vaccum, 12h3
4 5
Fig. 2.1 The sulfonium precursor route(SPR)
2.1.1.2 Side chain derivatization
The side chain approach involves the polymerization of a highly substituted monomer
to a soluble conjugated polymer that can be cast into thin films directly without
conversion. The polymerization of bis(halo methyl)benzene in the presence of a large
excess of potassium tert-butoxide to PPVs is referred to as Gilch route (Figure 2.2).8 It
65
proceeds through base-promoted 1,6-elimination of 1,4-bis(halomethyl)benzene
derivatives.9-12 This shortens the preparation of the conjugated polymer by two steps and
can increase the yields. The Gilch procedure is very simple and can normally result in
polymers with high molecular weights, narrow polydispersity indices and high structural
regularity. The Gilch route has been widely used for the preparation of soluble PPV
derivatives in order to avoid the conversion step and the many problems associated with
SPR.
CH2XXH2C
R
excess baseCH CH
R nX=Cl or Br
6 7
Fig. 2.2 The Gilch route
2.1.1.3 Polycondensation methods
Polycondensation methods can be differentiated into two types13: where the carbon
skeleton of PPV is generated in an olefinic reaction with formation of olefinic bond o
d aryl-olifine-
The most common
olycondensation method for the preparation of PPV is the Wittig method. This method
weight infusible yellowish fluorescence powder. An
r
where the PPV backbone is synthesized via a transition metal-catalyze
coupling with formation of the aryl-vinyl single bond.
p
tends to produce a low molecular
advantage of the Wittig step is that the structures of the resulting polymers are well-
defined and it allows a careful control of the molecular weight. Other widely used
polycondensation methods include the Heck reaction and McMurray reaction.
66
2.1.1.4 Ring-opening metathesis polymerization (ROMP)
Ring-opening metathesis polymerization (ROMP) offers the opportunity for precise
control of polydispersity and microstructure. The siloxy-substituted cyclophane 814 or
bicyclic monomer 1115 are typical substrates for ROMP. Precursor polymers 10 and 12
are converted to PPV 5 by thermal elimination (Figure 2.3).
OSiMe2tBu
tBuMe2SiO
n
HO
n
OCO2MeOCO2Me
MeO2CO OCO2Me n
n
[Mo(=NAr)(=CHMe2Ph)-{OCMe(CF3)2}2] Bu4NF
[Mo(=NAr)(=CHMe2Ph)-{OCMe(CF3)2}2]
1050C
HCl(g), 1900C
C
8 9
2800510
11 12
Fig. 2.3 Ring-opening metathesis polymerization (ROMP) route
67
2.1.2 Application of PPV and Derivatives
Much of early works on the application of PPV focused on the wide range of
conductivity that could be achieved. Although PPV can form highly conductive materials
as coatings for EMI/RFI shielding or antistatic application upon doping, the long-term
stability of these materials may be a problem. The application potential is in
photodiodes16, photovoltaic cell17,18, optocouplers19 and electrophotography20.
Polymer light-emitting devices (PLEDs) are the most intensely investigated area for
the application of PPV derivatives. PPV provides excellent hole-transporting layers21 in
PLEDs in addition to be the active emissive layer. With precisely chemical modifications
and device engineering, PPVs give colors which cover the entire visible spectrum of
colors with good efficiencies under a bias of only a few volts. In addition, the excellent
film-forming properties of PPVs suggest that a large area display can be fabricated from
these polymer materials. In summary, PPVs have great potential as commercial display
technologies of the future.22
2.2 Molecular design
There are mainly three categories of PPV derivatives. They are alkoxy-substituted23,
phenyl-substituted24,25 and naphthalene-containing PPV derivatives26. PPV compounds
have a good planarity due to their conjugated alkene skeleton. This planarity is important
for charge separating and transfer. But aggregation was also caused by the good planarity.
This aggregation will deduce the quantum yield and solubility of polymers. In our work,
we hope to introduce huge steric hindrance chromophores as side chains into the PPV
polymers. These side chains will combine their own properties together with the PPV
68
main chain and adjust the properties of polymers. The steric hindrance caused by these
side chains can be a favorite factor to decrease the aggregation and increase the
photoluminescence efficiency of polymers. By our knowledge, in all reported PPV
polymers, there is no dichromophore substituted PPV compounds. This may be due to the
synthesis problem. In this chapter, we try to synthesize dichromophore substituted PPV
polymers and test their basic optical-electric properties.
2.3 Synthesis route
Br
Br
Br
Br
Br
Br
Br
OMe
Br MeO
i ii
1 2 3
.
BrC6H13 C6H13
(HO)2BC6H13 C6H13
iii iv
4 5 6
Br
BC6H13 C6H13
v
7
O
O.
69
+Br
Br
OMe
MeO
2
OMe
MeOC6H13
C6H13
C H6 13
C6H13
vi
7 8
BO
O
3
C6H13 C6H13
Br
BrC6H13
C6H13
C6H13
C6H13
9
vii viii
n
10
.
Polymer P1 Scheme 2.1 The synthetic routes for the Polymer P1 Reagents and conditions: (i) NBS, benzoyl peroxide, CCl4, irradiation, reflux, 4h; (ii) Na, MeOH, 12h; (iii) n-C6H13Br, 50% NaOH, Bu4NBr, 80 oC, 24h; (iv) THF, BuLi, -78 oC, 2h, then trimethylborate to r.t. 24h; (v) 1,3-propanediol, toluene, reflux, 12h; (vi) Pd (PPh3)4 (5% mole), toluene/2M Na2CO3 , 100 oC, 48h; (vii) HBr gas/CHCl3, 24h; (viii) KO(t-Bu)/THF, 24h.
70
NH
NH
i ii
11 12 13
Br
N
Br
C6H13
.
iii
NC6H13
14
BO
O
.
+Br
Br
OMe
MeO
OMe
MeO
iv
1514
NC6H13
N C6H13
3
NC6H13
BO
O
2
v
Br
Br
NC6H13
N C6H13
N
vi
16 17
N
n
.
Polymer P2
71
Scheme2.2 The synthetic routes for the Polymer P2 Reagents and conditions: (i) NBS, DMF, reflux, 12h; (ii) n-C6H13Br, KOH, MeOH,50 oC, 24h; (iii) THF, BuLi, -78oC, 2h, then 2-isopropoxy-4,4,5,5-tetramethyl 1,3,2- dioxaboralane to r.t. 24h; (iv) Pd(PPh3)4 (5% mole), toluene/2M Na2CO3 , 100 oC, 48h; (v) HBr gas, CHCl3, 24h; (vi) KO(t-Bu)/THF, 24h. .4 Results and discussion.
2.4.1 Polymer synthesis
Compared with previous literature27,28,23,29,30, Our synthesis route has two distinct
advantage. First, the normal ways attached the two or one side chain groups on the xylene
ring first and then do the bromination of two methyl groups on the xylene later.
2
Br
Br
Br
Br
Br
Br
Br
Br
OMe
MeO
R
R
OMe
MeO
R
R
Br
Br
R
R
R
R
Br
Br
R=
i. NBS/C
Cl4
ii. Na/MeOH iii. Suzuki iv. HBr
v. Suzuki coupling
vi. NBS/CCl4
coupling
C6H13 C6H13
9
Figure 2.4 Protection and deprotection of -CH2Br group on difluorenyl benzene ring
For example, in the synthesis of Polymer P1, starting from 2,5-difluorenenyl-p-
xylenen, it is hard to obtain the pure compound 9 because of the alkyl chain in the
72
fluorene group will compete the bromination process with two methyl groups of
protect the CH2Br group first and then
o chromophores were attached. It avoids bromination on the two chromophore rings’
alkyl chains. This method highly improved the yield of bromination products. Second,
our deprotecting reaction of the CH Br group in CHCl3 with HBr gas is almost
quantitative reaction and there is no need to purify the product if the precursor is pure.
This is a big progress compared the general procedure by using 48% HBr water solution
(30-40%). By this way, two different chromophores can also be attached on one xylene
ring. It makes it possible to adjust the properties of PPV in a big range by using Gilch
polymerization.
It should be mentioned that the base and reactants concentration is important in Gilch
polymerization reaction. The potassium t-butoxide is 1M in this route. The reactants
concentration should be around 0.05 M. Too dilute solution gave a very low yield of the
final product. Too concentrated solution gave a gel product.
2.4.2 Size exclusion chromatography (SEC)
er P1 and P2
)
xylene.(Figure 2.4)
Our way has a bromination reaction on the two methyl group of compound 2,5-
dibromo-p-xylene. Methoxy group was chosen to
tw
2
Table 2.1 The SEC data of polym
Polymer Mn Mw Mw/Mn(PDI
P1 42300 70300 1.66
P2 57200 67400 1.18
73
Polymer P1 is green color. Polymer P2 is yellow green color. They can dissolve in
common organic solvents such as chloroform, THF, toluene. The molecular weights of
it shows weight loss at about 426 oC. At above 500 oC, there is about
the polymer P1 and P2 were determined by means of size exclusion chromatography
(SEC) using CHCl3 as an eluent and polystyrene as the standard. Their respective number
average molecular weights (Mn), weight average molecular weights (Mw) and
polydispersity indices (PDI) are outlined in Table 2.1.
2.4.3 Thermal Analysis (TGA and DSC)
The thermal stability of the polymer P1 and P2 were evaluated by thermogravimetric
analysis (TGA). P1 shows weight loss at about 370 oC in nitrogen (Figure 2.5). At above
512 oC, there is about 50% of residue, which was produced by charring during heating.
For Polymer P2,
56% of residue. We can see polymer P2 is much stable than P1.
100
110
100 200 300 500 600 700
70
80
90
400 80040
50
P1 P2
Wei
gh
t
60
(%
)
Te (0C)mperature
ig. 2.5 The thermogravimetric analysis (TGA) of Polymer P1 and P2 in a nitrogen atmosphere F
74
The first possible volatile fragment is the alky chain attached on the carbon atom of the
fluorene (P1) and nitrogen atom of carbazole (P2). After losing the alkyl chain, the
nitrogen radical is more stable than carbon radical. That is the reason why P2 is more
stable than P1.
50 100 150 200 250
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
P1
Hea
tw
(W
/g)
0
Flo
Temperature (C)
P2
Fig. 2.6 The DSC traces of Polymer P1 and P2
Thermally induced phase transition behavior of P1 and P2 was also investigated with
differential scanning calorimetry (DSC) in a nitrogen atmosphere. The DSC curves are
shown in Figure 2.6. From these curves, we can see P1 and P2 have no obvious Tg. The
relatively high glass transition temperatures are essential for many applications, such as
emissive materials in light –emitting diodes.
2.4.4 Optical Properties (UV and PL)
The spectroscopic properties of the target polymers were measured in chloroform
roperties are summarized in Table 2.2. solution. The optical p
75
P1 exhibited the absorption maximum at 321 nm, with a small shoulder at 286 nm and
a sub-peak at 421 nm. Its PL spectrum peaked at 481 nm with a sub-peak at 381nm. P2
exhibited the absorption maximum at 301 nm with an emission at 497 nm (Figure 2.7). In
general, the presence of well-defined vibronic structures in the emission spectra indicates
at the polymer has a rigid and well-defined backbone structure.31,32 th
300 400 500 600 7000.0
0.2
0.4
0.6
0.8
1.0
1.2
0
200
400
600
800
1000
1200
Ab
so
rpti
on
(N
orm
aliz
ed
)
Wavelength (nm)
P1 Uv P1 PL P2 Uv P2 PL
PL
Inten
sity
(a.u.)
Fig. 2.7 The UV-vis absorption spectra and photoluminescence spectra of Polymer P1
Table 2.2 The optical data and fluorescence quantum yields (both in chloroform
and P2 measured from their chloroform solution at room temperature
solutions) of polymer P1 and P2
Solution λmax(nm)a Eg(eV)b PL Efficiency (%)
compound Abs. Em
P1 321(286, 421) 481(381) 3.18 76.0
P2 301 497 3.66 54.0
a. The data in the parentheses are the wavelength of shoulders and sub-peaks;
UV absorption. b. Eg stands for the band gap energy estimated from the onset wavelength of the optical
76
350 400 450 500 550 6000
50
100
150
200
250
300 CHCl
3
THF 90% THF, 10% MeOH 80% THF, 20% MeOH 20% THF, 80% MeOH 3% THF, 97% MeOH
ten
sit
(a.u
.)
PL
Iny
Wavelength (nm)
Fig. 2.8 Solvent effection on linear photoluminescence spectra of polymer P1
As shown in Figure 2.8, polymer P1 has two emission peaks. One is for the emission
of PPV backbone (around 480nm);23 the other is for the emission of PPV side
chromophore chains (around 380nm).33-35 With the different ratio of good solvent (THF
and chloroform) and poor solvent (MeOH), the area of two PL emission peaks have
obvious change. This property is very useful in biosensor detection.36,
and P2 was investigated by the Cyclic
Voltammetry (CV). The CV was performed in a solution of Bu4
temperature under the protection of argon. A
platinum electrode was used as the working electrode. A Pt wire was used as the counter
electrode and an Ag/AgNO3 electrode was used as the reference electrode. The
corresponding data are summarized in Table 2.3 and Figure 2.9.
37
2.4.5 Electrochemical Properties
The electrochemical behavior of polymer P1
NClO4 (0.10M) in
chloroform at a scan of 50 mV/s at room
77
Table 2.3 The electrochemical data of the polymers P1 and P2
a. LUMO energy level was calculated by Eg and HOMO energy level
0 1 2-1
0
2
1
4
5
3
I (m
A)
(
-2 -1 0 1 2-6
-2
2
no
r
E (V vs SCE)
P1
m.)
4
6
-4
0
8
10
I (m
A)
(
Fig. 2.9 The cyclic voltammograms of P1 and P2
no
r
E (V vs SCE)
P2
P2 has
aromatic CH2Br groups’
d deprotection reactions. The high yields of these two reactions were
uarantee of the success of whole route.
p-doping (V) Energy levels(eV) compound
Eonset Epa Epc HOMO LUMO Eg
P1 1.20 1.66 1.38 -5.60 -2.42a 3.18
P2 1.25 1.79 1.41 -5.65 -1.99 3.66
m.)
P1 and P2 have almost the same HOMO energy level (-5.60 and -5.65eV), but
a 0.4 eV higher LUMO energy level (-1.99 vs -2.42 eV). P2 is better to be used as hole
transporting materials and P1 is better to be used as emission layer materials.
2.5 Conclusion
Two novel dichromophore side chains substituted PPV compounds were successfully
synthesized. Two key steps in the whole synthesis route were
protection an
g
78
Efficient green light emission, good solubility in common organic solvents, good
thermal stability and relative high glass transition temperatures had been demonstrated in
nds. These properties made the two polymers good candidatures for efficient
green light em vices. In the mean , by o sis is poss to
attach different chromophore functio oups a chains V com s.
This will highly ase the l energy
two compou
itting de time ur synthe route, it ible
s and nal gr s side- on PP pound
incre orbita level tuning range of PPV compounds.
79
Reference
G. Chem. Abstr. 1968, 69, 87735q.
. Gilch, H. G.; Wheelwright, W. L. J. Polym. Sci., Part A: Polym. Chem. 1966, 4,
1337.
. Doi, S.; Kuwabara, M.; Noguchi, T.; Ohnishi, T. Synth. Met. 1993, 57, 4174.
0. Heeger, A. J.; Braun, D. Chem. Abstr. 1993, 118, 157401j.
1. Sarnecki, G. J.; Burn, P. L.; Kraft, A.; Friend, R. H.; Holmes, A. B. Synth. Met.
1993, 55, 914.
2. Swatos, W. J.; Gordon, B. Polym. Prepr. 1990, 31, 505.
3. Scherf, U. Top. Curr. Chem. 1999, 201, 163.
4. Miao, Y. J.; Bazan, G. C. J. Am. Chem. Soc. 1994, 116, 9379.
5. Conticello, V. P.; Gin, D. L.; Grubbs, G. H. J. Am. Chem. Soc. 1992, 114, 9708.
6. Yu, G.; Pakbaz, K.; Heeger, A. J. Appl. Phys. Lett. 1994, 64, 3422.
1. Burroughes, J. H.; Bradley, D. D. C.; Brown, A. R.; Marks, R. N.; MacKay, K.;
Friend, R. H.; Burn, P. L.; Holmes, A. B. Nature 1990, 347, 539.
2. Kraft, A.; Grimsdale, A. C.; Holmes, A. B. Angew. Chem. Int. Ed. 1998, 37, 403.
3. Wessling, R. A.; Zimmerman, R.
4. Wessling, R. A. J. Polym. Sci. Polym. Symp. 1985, 72, 55.
5. Lenz, R. W.; Han, C.-C.; Stenger-Smith, J.; Karasz, F. E. J. Polym. Sci. Polym.
Chem. 1988, 26, 3241.
6. Burn, P. L.; Bradley, D. D. C.; Friend, R. H.; Halliday, D. A.; Holmes, A. B.;
Jackson, R. W.; Kraft, A. J. Chem. Soc. Perkin Trans. 1 1992, 3225.
7. Garay, R. O.; Baier, U.; Bubeck, C.; Müllen, K. Adv. Mater. 1993, 5, 561.
8
9
1
1
1
1
1
1
1
80
17. Antoniadis, H.; Hsieh, B. R.; Abkowitz, M. A.; Jenekhe, S. A.; Stolka, M. Synth.
Met. 1994, 62, 265.
8. Karg, S.; Reiss, W.; Meier, M.; Schwoerer, M. Synth. Met. 1993, 55, 4186.
9. Yu, G.; Zhang, C.; Pakbaz, K.; Heeger, A. J. Synth. Met. 1995, 71, 2241.
0. Drefahl, G.; Hörhold, H.-H.; Opfermanm, J. GDR Patent 75233, 1970.
1. Brown, A. R.; Bradley, D. D. C.; Burroughes, J. H.; Friend, R. H.; Greeham, N.
C.; Burn, P. L.; Holmes, A. B.; pl. Phys. Lett. 1992, 61, 2793.
22. Light-Emitting Polymers: The Technology and Opportunities; Technical Insights
23.
Appl. Phys. 1993, 32,
27. H. S.; Huang, W.; Xu, Y. S.; Cao, Y. Macromolecules
28. r, I. D.; Cao,
H. Adv. Mater. 1998, 10, 1340.
32,
1
1
2
2
Kraft, A. Ap
Inc., 1996.
Braun, D.; Heeger, A. J. Appl. Phys. Lett. 1991, 58, 1982.
24. Peng, Z. H.; Pan, Y. C.; Xu, B. B.; Zhang, J. H. Macromol. Symp. 2000, 154, 245.
25. Peng, Z. H.; Zhang, J. H.; Xu, B. B. Macromolecules 1999, 32, 5162.
26. Onada, M.; Uchida, M.; Ohmori, Y.; Yoshino, K. Jpn. J.
3895.
Chen, Z. K.; Nancy, L.
2003, 36, 1009.
Becker, H.; Spreitzer, H.; Kreuder, W.; Kiuge, E.; Schenk, H.; Parke
Y. Adv. Mater. 2000, 12, 42.
29. Spreitzer, H.; Becker, H.; Kluge, E.; Kreuder, W.; Schenk, H.; Demandt, R.;
Schoo,
30. Becker, H.; Spreitzer, H.; Ibrom, K.; Kreuder, W. Macromolecules 1999,
4925.
81
31. Miyaura, N.; Yamada, K.; Suginome, H.; Suzuki, A. J. Am. Chem. Soc. 1985, 107,
972.
32. Suzuki, A. Pure Appl. Chem. 1985, 57, 1749.
33. Pei, Q. B.; Yang, Y. J. Am. Chem. Soc. 1996, 118, 7416.
2000, 12,
37. Kohler, B.; Korystov, D.; Mikhailovsky, A.; Bazan, G. C. J.
34. Bernius, M. T.; Inbasekaran, M.; OBrien, J.; Wu, W. S. Adv. Mater.
1737.
35. Ranger, M.; Leclerc, M. Macromolecules 1997, 30, 7686.
36. Liu, B.; Bazan, G. C. J. Am. Chem. Soc. 2004, 126, 1942.
Woo, H. Y.; Liu, B.;
Am. Chem. Soc. 2005, 127, 14721.
82
Chapter Three
ymers
3.1 Introduction
Conjugated organic compounds play a primary role in the development of a new
generation of optical and electronic materials. Small molecules, oligomers, and polymers
with carbon, heteroatomic, or organometallic frameworks have been widely explored as
media for electroluminescence, data storage, and nonlinear optics.1,2 The most intensely
studied conjugated molecules with carbon-rich frameworks focus on extended linearly-
conjugated π-systems.
During the 20th century, the interest of organic chemists was captured by the definition
of aromaticity based on theoretical principles and on the power of those principles to
guide the synthesis of novel nonbenzenoid aromatic compounds.
Fulvalenes are molecules with two unsaturated ring systems showing cross conjugation
through the interring double bond and capable of generating two separate aromatic
moieties.4-10 Tetrabenzo[5.5]fulvalene, a basic bistricyclic aromatic system, was widely
used to study its aromaticity by energetic, structural (geometric), and magnetic
escriptors of aromaticity.11-15 By our knowledge, no report has been made on
trabenzo[5.5]fulvalene’s usage in materials. Our target is to synthesize
trabenzo[5.5]fulvalene based polymer. We hope to explore how the
trabenzo[5.5]fulvalene make an effect on polymer properties and find the potential
pplication for polymers .
Synthesis and characterization of tetrabenzo[5.5]fulvalene
based pol
3
d
te
te
te
a
83
O
BrH
iii
iii iv
Scheme 3.1 General synthesis routes of tetrabenzo[5.5]fulvalene. i) CrO3/CH3COOH; ii) TiCl4/Zn, THF; iii) NBS/benzene; iv) KOH/DMSO. There are two general ways to obtain the tetrabenzo[5.5]fulvalene (Scheme3.1). But by
these two ways only the symmetric structure can be obtained. For the nonsymmetric
structure tetrabenzo[5.5]fulvalene, we can only choose the route in Scheme 3.2.11
3.2 Molecular design
Br Br Br Br
O
i.
1 2
Br Br
O
Br Br+
ii
.
3 2 4
Scheme 3.2 Synthesis routes for monomer 4. Reagents and conditions: (i)CrO3/ CH3COOH; (ii) a) 1 equiv. BuLi, Si(Me)3 Cl/ THF; b) 1 equiv. BuLi.
84
Br BrBrBr B(OH)2(HO)2B
iii
1 6
iv
5
vBO
O BO
O
7
.
NH N
H
Br Br
N
Br Brvi vii
.
8 9 10
N
viii BO
OBO
O
11
Scheme 3.3 Synthesis routes for monomer 7 and 11. Reagents and conditions: (iii) n-C6H13Br, 50% NaOH, Bu4NBr, 80 C, 24h; (iv) THF, BuLi, -78 C, 2h, then trimethylborate to r.t.; (v) 1,3-propanediol, toluene, reflux, 12h; (vi) NBS, DMF, reflux, 12h; (vii) n-C6H13Br, KOH, MeOH, 50 C, 24h; viii) THF, BuLi, -78oC, 2h, then 2-isopropoxy-4,4,5,5-tetramethyl 1,3,2- dioxaboralane to r.t.
.
o o
o
85
Br Br
+ ix
n
BO
OBO
O
7 4 12
Polymer P1
N
B O
OBOO
11
Br Br
N
n
+ix
4 13
Polymer P2
Scheme 3.4 Synthesis routes for polymer P1 and P2. Reagents and conditions: (ix) Pd(PPh3)4 (5% mole), toluene/2M Na2CO3 , 100 oC, 48h; In Scheme 3.2, 9-trimethylsilylfluorene was first formed by using trimethylsilyl
chloride and fluorene in the condition of 1 equivalent of n-Butyllithium. Then another 1
equivalent of n-Butyllithium was used to remove the remaining proton atom from 9
position of fluorene. This negative ion reacted with 2, 7- dibromofluorenone to obtain the
final product 9-(9H-Fluoren-9-ylidene)-2, 7-dichloro-9H-fluorene.
86
3.3 Results and discussion.
3.3.1 Size exclusion chromatography (SEC)
Table 3.1 The SEC data of polymer P1 and P2
Polymer Mn Mw Mw/Mn
P1 7200 11300 1.58
P2 5500 7000 1.28
Polymer P1 and polymer P2 are brown yellow color. They can dissolve in common
organic solvents, such as chloroform, THF, toluene. The molecular weights of the
polymer P1 and P2 were determined by means of size exclusion chromatography (SEC)
using CHCl3 as an eluent and polystyrene as the standard. Their respective number
average molecular weights (Mn), weight average molecular weights (Mw) and
polydispersity indices (PDI) are outlined in Table 3.1. The molecular weight of P1 and
P2 are not high because the planar structure of tetrabenzo[5.5]fulvalene units make the
whole molecule to be good packing and reduce the solubility in the reaction solvent.
3.3.2 Thermal Analysis (TGA and DSC)
The thermal stability of the polymers in nitrogen was evaluated by thermogravimetric
analysis (TGA). P1 shows weight loss at about 327 oC in nitrogen. Above 570 oC, there is
about 60% of residue, which was produced by charring during heating. P2 shows weight
loss at about 335 oC in nitrogen (Figure 3.1). Above 470 oC, there is about 67% of residue.
All these indicate a good thermal stability.
87
88
Fig. 3.1 The thermogravimetric analysis (TGA) of P1 & P2 in a nitrogen atmosphere
Thermally induced phase transition behavior of P1 and P2 was also investigated with
differential scanning calorimetry (DSC) in a nitrogen atmosphere (Figure 3.2).
0 100 200 300 400 500 600 700 80050
60
70
80
90
100
Wei
gh
t(%
)
Temperature (0C)
P1 P2
50 100 150 200-1.8
-1.6
-1.2
-1.4
-0.8
-1.0
t F
lo(W
/g)
Hea
w
Temperature (0C)
P1 P2
Fig. 3.2 The DSC traces of P1 and P2
The DSC curves are shown in Figure 3.2. From these curves, we can see P1 has a Tg at
6 oC. This shows the introducing of carbazole units into the
gmental movement of the polymer chain.
y chain attached on
the carbon atom of the fluore 1) and nitrogen ato carbazole (P2
the alkyl chain, the nitrogen radical is more stable than carbon radical. That is the reason
why P2 more stable than he relatively high transition temp es are
ential for many applications, such as emissive materials in light –emitting diodes.16
rigid
nd well-defined backbone structure.
115 oC and P2 has a Tg at 17
polymer mains has a profound effect on the se
In the heating process, the first possible volatile fragment is the alk
ne (P m of ). After losing
is P1. T glass eratur
ess
3.3.3 Optical Properties (UV and PL)
The spectroscopic properties of the target polymers were measured in chloroform
solution. The optical properties are summarized in Figure 3.3 and Table 3.2.
P1 exhibited the absorption maximum at 369 nm, with a sub-peak at 466 nm. Its PL
spectrum peaked at 411 nm. P2 exhibited the absorption maximum at 312 nm, with a
sub-peak at 467 nm. Its PL spectrum peaked at 487 nm. In general, the presence of well-
defined vibronic structures in the emission spectra indicates that the polymer has a
a
89
ig. 3.3 The UV-vis absorption spectra and photoluminescence spectrum of Polymer P1 and P2 measured from their chloroform solution at room temperature
Table 3.2 The optical data and fluorescence quantum yields (both in chloroform solutions) of polymer P1 and P2
Solution λmax(nm)a Eg(eV)b PL Efficiency (%)
300 400 500 600 7000.0
0.2
0.4
0.6
0.8
1.0
1.2
0
200
400
600
800
1000
1200
Ab
sorp
tio
n (
No
rma
lized
)
Wavelength (nm)
P1 UV P2 UV P1 PL P2 PL
PL
Inten
sity
(a.u.)
F
compound Abs. Em
P1 369 (466) 411 3.00 20%
P2 312 (467) 487 3.26 12%
a. The data in the parentheses are the wavelength of shoulders and sub-peaks; b. Eg stands for the band gap energy estimated from the onset wavelength of the optical UV absorption. Polymer P1 and P2 have relatively lower photoluminescence efficiency (20% and
18%). Their tetrabenzo[5.5]fulvalene units in polymer caused a good packing which can
quench the emission.
90
3.3.4 Electrochemical Properties
The electrochemical behavior of polymer P1 and P2 were investigated by the Cyclic
Voltammetry (CV). The CV was performed in a solution of Bu4NClO4 (0.10M) in
chloroform at a scan of 50 mV/s at room temperature under the protection of argon. A
platinum electrode was used as the working electrode. A Pt wire was used as the counter
electrode and an Ag/AgNO3 electrode was used as the reference electrode. The
corresponding data are summarized in Figure 3.3 and Table 3.3.
-1 0 1 2-1
0
1
2
3
4
5
6
I (m
A)
(n
0
2
o
E (V vs SCE)
P1
rm.)
0 1 2-2
4
6
I (m
A)
(no
rm.)
E (V vs SCE)
P2
ers P1 and P2
p-doping (V) Energy levels(eV)
Fig3.4 The cyclic voltammograms of P1 and P2
Table 3.3 The electrochemical data of the polym
compound
Eonset Epa Epc HOMO LUMOa Eg
P1 1.10 1.67 1.45 -5.50 -3.16 2.34
P2 0.91 2.00 1.44 -5.31 -3.02 2.29
a. LUMO energy level was calculated by Eg and HOMO energy level
91
3.3.5 Comparison of our novel polymers with some analogues
Table 3.4 comparison of polymer P1, P2 with analogues
Polymers Absorption
(λm)
Emission
(λm)
Band gap(eV)
/PL efficiency (%)
C6H13 nC6H13
Fl-Fl-C617
379 415 2.86/82.22
C6H13 nC6H13NC8H17 17Fl-C6-CB-C8
348 398 3.06/26.3
C6H13 nC6H13
18Fl-C6-SpirobiFl
.6 425(EL) N.A. N.A./34
C6H13C6H13
n P1
369 411 3.00/20
N
n
C6H13
P2
312 487 3.26/12
The UV absorption, PL emission, band gap and PL efficiency of our novel polymer P1,
ads to the essential lowering of the energy of the fluorescent term
P2 and some analogues are shown in Table 3.4. It is interesting that polymer P2 has the
biggest Stokes shift. This shows that Polymer P2 undergoes noticeable flattening in their
excited state, which le
92
and, in turn, enlargement of the Stokes shift of the fluorescence.19 Polymer P1 has almost
ers were successfully
synthesized. The key step in the whole synthesis route was the synthesis reaction of
dibromo-tetrabenzo[5.5]fulvalene.
Good solubility in common organic solvents, good thermal stability and relative high
glass transition temperatures had been demonstrated in these two compounds. Although
the quantum yield of the two polymers were low due to the good packing of the
tetrabenzo[5.5]fulvalene units. This kind of compounds can still have the potential to be
used in solar cell and organic field effect transistor. In the meantime, this is the first time
to introduce tetrabenzo[5.5]fulvalene units into polymer compounds. We hope to explore
more properties of this kind of polymers in the future research work.
the same absorption, emission and band gap with polyfluorene (F1-F1-C6). But its PL
efficiency is much lower than polyfluorene(F1-F1-C6). This quantum yield quenching
was caused by the good packing of tetrabenzo[5.5]fulvalene units.
3.4 Conclusion
Two novel tetrabenzo[5.5]fulvalene units containing polym
93
Reference
1. Meier, H. Angew. Chem., Int. Ed. 2005, 44, 2482.
2. Martin, R., E.; Diederich, F. Angew. Chem. Int. Ed. 1999, 38, 1350.
3. Gholami, M.; Tykwinski, R. R. Chem. ReV. 2006, 106, 4997.
Kleinpeter, E.; Holzberger, A.; Wacker, P. J. Org. Chem. 2008, 73, 56.
5. Mills, N. S.; Malandra, J. L.; Hensen, A.; Lowery, J. A. Polycyclic Aromatic
, 239.
6. Bagrat A, S.; Anja, F.; Erich, K. J. Phys. Chem. A 2008, 112, 10859.
7. Shainyan, B. A.; Fettke, A.; Kleinpeter, E. 2008,
8. Piekarski, A. M.; Mills, N. S.; Yousef, A. J. Am. Chem. Soc.
9. Dahl, B. J.; Mills, N. S. Org. Lett. 2008, 10, 5605.
10. Pogodin, S.; Agranat, I. J. Org. Chem. 2007, 096.
11. Mills, N. S.; Burns, E. E.; Hodges, J.; Gibbs, J.; Esparza, E.; Malandra, J. L.;
Koch, J. J. Org. Chem. 1998, 63, 3017.
12. ls, N . J. Am. Chem. Soc. 2008, 130, 10179.
13. Mills, N. S.; Benish, M. Journal of Organic Chemistry 2006, 71, 2207.
14. Levy, A.; Rakowitz, A.; Mills, N. S. J. Org. Chem. 2003, 68, 3990.
15. Mills, N. S. J. Am. Chem. Soc. 1999, 121, 11690.
16. Tokito, S.; Tanaka, H.; Noda, K.; Okada, A.; Taga, Y. Appl. Phys. Lett. 1997, 70,
1929.
17. Liu, B.; Yu, W. L.; Lai, Y. H.; Huang, W. Chem. Mater. 2001, 13, 1984.
4.
Compounds 1998, 12
J. Am. Chem. Soc. 112, 10895.
2008, 130, 14883.
72, 10
Dahl, B. J.; Mil . S
94
18. Yang, C. M.; Liao, H. H.; Horng, S. F.; Meng, H. F.; Tseng, S. R.; Hsu, C. S.
Synth. Met. 2008, 158, 25.
19. Doroshenko., A. O.; Kirichenko., A. V.; Mitina, V. G.; Ponomaryov, O. A.
Journal of Photochemistry and Photobiology A: Chemistry 1996, 94, 15.
95
Chapter Four
Synthesis and Characterization of Chromophore Substituted
[2.2]Paracyclophane Derivatives
.1 Introduction
Cyclophane, a name first proposed by D. J. Cram,1 was originally defined as a
olecule that possesses layered aromatic moieties or a molecule that has bridges across
e plane of an aromatic moiety. Cyclophane, in which two benzene rings are close to
ach other and cofacial, is attractive in its structure, reactivity and physical properties.2,3
Although drawn flat for clarity, ring strain distorts substantially the aromatic rings. The
distance between bridgehead carbons on opposing rings is ~ 2.78 Å, while the distance
arbon bonds is ~ 3.09 Å.3 In
ent ne-containing
yme materials.
4
m
th
e
between rings measured from the nonbridging carbon-c
rec years, the cyclophane compounds research focused on cyclopha
pol rs, cyclophane chiral ligands and cyclophane nonlinear optical
Side view Top View(pCp)
Fig. 4.1 Paracyclophane
4.1.1 Cyclophane-containing Polymers
Cyclophanes have optically, electrically, and topologically intriguing features.3-5 The
addition of cyclophane compounds in polymer main chains as well as polymer side
chains as pendent groups can lead to potential applications of the resulting polymers.6
96
4.1.1.1 [2, 2] Paracyclophane-containing conjugated polymers
mers with extended conjugation contain Poly ing [2.2]paracyclophane were reported in
othienyl-substituted
groups.7-10
the 2000s. The electrochemical polymerization of olig
paracyclophanes was performed independently by two research
SS
SS
SS
SS
Electrolicpolymerizatiom
n
units
[2.2]paracyclophane unit were prepared by Prof. Y. Chujo’s group11-20 through
21,22 23-25
and Su o afford
ell-defined and well characterized [2.2]paracyclophane-containing conjugated polymers
ue to copolymerization with aromatic compounds possessing long alkyl chains.
Fig. 4.2 Conjugated polymers including oligothiophene and [2.2]paracyclophane
As shown in Figure 4.3, conjugated polymers containing a repeating
palladium-catalyzed cross-coupling reactions, i.e., Sonogashira , Mizoroki–Heck
zuki–Miyaura26,27 coupling reactions. These reactions enabled them t
w
d
OC12H25
C12H25O
nOC12H25
C12H25O
Fe
CC12H25
C12H25
n
Fig. 4.3 Main-chain-type [2.2]paracyclophane-containing conjugated polymers.
97
4.1.1.2 Rigid-rod conjugated polymers containing pendent aromatic rings
A linear conjugated polymer possessing aromatic rings as a pendent group was
esigned and synthesized by our group(type B).28-31 For example, a series of
ithia[3.3]paracyclophane-fluorene copolymers were synthesized by employing the
uzuki–Miyaura coupling reaction. The external aromatic group affects the electronic
nd optical properties of the polymer backbone through the transannular π–π interaction.
he PL efficiency of some polymers was enhanced or significantly decreased by the
endent aromatic rings. Intramolecular electron transfer from the polymer main chain to
e external aromatic rings occurred via the through-space interaction.
d
d
S
a
T
p
th
- system
- system
ty
pe A
.
S
- systemS
S
S
S
S - system
type B
.
98
SC6H13
C6H13
SRR n
SC6H13
C6H13
S n
R=H,
=75%
R=OMe,
R=CN, =0%PL
PL
PL
=36%
PL =50%
PL =5%
PL =78%
In Figure 4.5, the polymer contains bipyridinophane as the pendent unit in the
phenylene-fluorenylene polymer backbone31. It exhibited red-shifts of the absorption and
emission spectra in comparison with phenylene-fluorenylene without the bipyridinophane
nit, and they occurred due to the intramolecular edge-tilted T intramolecular aromatic
Fig. 4.4 Dithia[3.3]paracyclophane-fluorene copolymers
u
C–H/π interaction. The ion-sensing properties were studied. The fluorescence of the
polymer was efficiently quenched due to the presence of transition-metal cations such as
Cu2+, Co2+, Ni2+, Zn2+, Mn2+, and Ag+.
99
hv X
S
C6H13C6H13
SN
N
HH
n
S
C6H13C6H13
SN
N
HH
n
Mn+
Mn+
Mn+= Cu2+, Co2+, Ni2+Zn2+, Mn2+, Ag+
.1.2 Cyclophane chiral ligands
Chiral [2.2]paracyclophane derivatives have found considerable use in stereoselective
and their
Fig. 4.5 The detection of Mn+ by dithia[3.3]paracyclophane-fluorene polymers
4
synthesis. They undergo racemisation only at relatively high temperatures,
cyclophane backbone is chemically stable towards light, oxidation, acids and bases.32-35
The majority of [2.2]paracyclophane ligands or reagents are based on one of five
different substitution patterns(Figure 4.6).36
R1
mono ortho
R1
R2R2R1
pseudo-ortho pseudo-geminal bridge substituted
R1
R2 R1
R2
Fig. 4.6 [2.2]Paracyclophane substitution patterns and ligands.
Unlike other common planar chiral scaffolds, such as metallocenes or metal–arene
complexes that require two (or more) substituents on one ring to become chiral,
[2.2]paracyclophane only requires one substituent to break the symmetry of the molecule.
100
Prior to the advent of PHANEPHOS 4,12-bis(diphenylphosphino)
[2.2]paracyclophane , a pseudo-ortho disubstituted derivative, as chiral ligand in 1997,37-
39 few results on the use of [2.2]paracyclophane in stereoselective synthesis were reported.
The results obtained with PHANEPHOS and related compounds suggest that cyclophanes
bearing donor atoms on both rings may be viewed as a highly selective class of ligand
omparable with some of the best ligand classes available for asymmetric catalysis such
s the binaphthyl backbone of BINAP and the 1, 2-disubstituted ferrocene backbone of
SIPHOS. It is thus of considerable interest to develop new synthetic approaches to
chiral cyclophanes bearing both identical and non-identical substituents on their two rings.
It is the great success of PHANEPHOS in enantioselective hydrogenations that has
fuelled research into the utility of [2.2]paracyclophane as a scaffold for the preparation of
chiral ligands.
Planar chiral monosubstituted [2.2]paracyclophane derivatives have been employed in
asymmetric diisopropylzinc additions to aldehydes, asymmetric cyclopropanation
reactions and asymmetric epoxidation reactions.40-44 These pioneering studies as shown
in Figure 4.16 have produced moderate to excellent enantioselectivities and yields.45 But
most of the monosubstituted [2.2]paracyclophane derivatives majority show moderate to
low enantioselectivities, presumably due to excessive conformational freedom.46
4.1.3 Cyclophane nonlinear optical materials.
In recent years, almost all of the research work on cyclophane containing nonlinear
optical materials was done by Professor Bazan’s group,47 they set out to synthesize
precisely determined molecular structures that bring together two chromophores into
,
c
a
JO
101
close proximity and would make it possible to probe the effect of orientation, contact site,
and the length of electronic delocalization on the optical properties. The goal was to
better understand the problems of “through-space” delocalization. Their strategy was to
take advantage of the paracyclophane framework48-50 as the site of interchromophore
contact51,52 since it enforces cofacial overlap of two aromatic rings, minimizes
tramolecular motion, and has proven useful for the study of π-π electron delocalization
and ring strain in several organic compounds.
Calculations predicted that more facile charge transport could be achieved by a
monolayer of strongly interacting conjugated molecules due to the formation of a pseudo
two-dimensional band structure in the molecular layer.53 Building an interdigitated
molecular bilayer using [2.2]paracyclophane allows one to obtain the necessary strong
electronic coupling while at the same time enforcing a cofacial relationship between the
ctive units.
[2.2]paracyclophanes
in
a
4.1.3.1 Synthesis and characterization of chromophores substituted
CMe3Me3C
CMe3Me3C
Me3C
Me3C CMe3
CMe3
Fig. 4.7 Tetra- substituted Cyclophanes.
102
Two molecules in Figure 4.7 display electronic delocalization throughout their
structures makes them interesting within the context of three-dimensional conjugation.
Such molecular systems are described by symmetry elements not contained within the
structures of linear or two-dimensional analogues. The [2.2]paracyclophane framework
unit that is
me
n’s studies, a successful approach had been put forth that involved a
provides a suitable backbone in the form of a polarizable transmitting
amenable for subsequent functionalization. For this effort, they collaborated with the
research groups of Professors Joe Zyss and Shaul Mukamel to provide a combined
synthesis, spectroscopy, and theory effort to understand the potential and limitations of
higher sym try nonlinear optical chromophores.54
For constructing a rationale for the structure/optical properties relationships in the class
of compounds in these molecules, the collective electronic oscillator (CEO) approach was
used. CEO approach55-57 demonstrated previous success at describing the optical response
of chromophore aggregates. This technique computes molecular vertical excitation
4.1.3.2 Two photon absorption (TPA) performance of paracyclophanes
Organic molecules that exhibit large two-photon absorption (TPA) cross sections (δ)
are relevant to emerging technologies such as three-dimensional optical data storage,58,59
photodynamic therapy,60,61 two-photon optical power limiting,62-66 and two photon three-
dimensional microfabrication.67-74 Coordinated synthetic, spectroscopic, and theoretical
studies have yielded insight into how to better design molecules with large δ values. In
Professor Baza
framework for mobile π-electrons with electron donor/acceptor groups on the terminal
sites with or without donor/acceptor groups in the middle of the conjugated framework.75
The collective electronic oscillator (CEO) method indicates extensive delocalization
103
throughout the entire molecule. Such quadrupolar systems provide the potential for
symmetric charge displacement upon excitation and enhanced TPA. (Figure 4.8)
NHex2Hex2N
NHex2Hex2N
Hex2N NHex2
NHex2Hex2N
Figure 4.8 Quadrupolar cyclophane systems
4.1.3.3 Charge transport through paracyclophanes
The research work on charge transport of covalently linked chromophores across a
single molecule or a single molecular layer was reported.76 Experiments have
demonstrated that molecules addressed in parallel act as independent conductance
channels,77-79 namely, an ensemble of mole
cules behaves the sum of the individual
molecular conductances.
SAc
AcS
SAc
AcS
are embedded within the complex mixture of
Fig. 4.9 Cyclophane molecular structures used for charge transport
In conclusion, the work on [2.2]paracyclophane structures provides a useful tool to
probe optical and electronic properties that
sites characteristic of organic materials.
104
4.2 Molecular Design
Direct bromination of [2, 2] parcyclophane47 was used in almost all of the works to
obtain the desired cyclophane bromides from which functional groups can be attached on.
There are three shortages of this method. First, Because the eight carbons on the two
aromatic benzene rings of the[2, 2] paracyclophane had same reactivity, bromination
products of [2, 2] paracyclophane were very complicated, which caused burdensome
works on separation and very low52 (normally < 20%) yields of desired bromides. Second,
only the same functional groups can be attached on the cyclophanes because of the same
activity of bromine atoms on the cyclophanes rings. This heavily limited the properties
tunability of cyclophanes derivatives. Third, the yields of extension reactions of
cyclophanes were not high due to the forming of different substitution byproducts which
also caused the separation problem.
80
52
PPh
PPh
2
2
SS
n
C8H17
C8H17
R
R
R
R
R
R
R
R
Br
Br
Br
Br
Br
Br
Br
Br
Fig. 4.10 Normal ways to construct cyclophane derivatives structures
105
We hope to construct cyclophane core by using coupling reaction. By this method, we
can attach the wanted functional groups on the two aromatic benzene rings first. Then we
can use two same or different substituted benzene rings to form the cyclophane core. This
gives us wider choice to introduce different functional groups on the cyclophane cores.
For example, some electro-withdrawing groups on one ring and some electron-donating
group on another ring, these two rings coupling will form a donator-π delocalization-
acceptor molecule and makes cyclophane cores more easily to reach our target molecule.
The highly increased tunability will strongly stimulates the application of cyclophane
derivatives. In our whole synthesis route, we estimate that the key step is the coupling
reaction and hope the other steps reactions yields should be satisfactory. The
retrosynthetic analysis is shown in Figure 4.11
R1
R1
R2
R2
R1
R1
OMe
MeO
R2
R2
Br
Br
OMe
MeO
Br
Br
Br
Br
Br
Br
Br
Br
R2
R2
SH
HS
Br
R1
R1
Br
OMe
R2
R2
MeO
Fig. 4.11 Retrosynthetic analysis of target tetrasubstituted [2.2]paracyclophane
106
4.3 Synthesis and characterization
4.3.1 Synthesis of (4,7,12,15)-Tetra(9,9-di-n-hexyl-fluoren-2-yl) [2,2]paracyclophane
(2F2F)
Br
Br
Br
Br
Br
Br
MeO
Br
Br
i ii.
OMe
1 2 3
BrC6H13 C6H13
(HO)2BC6H13 C6H13
iii iv
4 5 6
Br
v OB
C H6 13 C H6 13
7
O.
+Br
Br
OMe
MeO MeO
2
OMe
C H6 13
C6H13
C6H13
C6H13
vi
7 8
BC6H13 C6H13
O
O
3
107
Br
BrC6H13
C6H13
C6H13
C6H13
SH
HSC6H13
C6H13
C6H13
C6H13
9 10
vii viii
C6H13
C6H13
C6H13
S
C6H139 + 10
SC6H13
C6H13
C6H13
11 (DiS2F2F)
ix
C6H13
C6H13
C6H13
C6H13
C6H13
C6H13
C H6 13
C H6 13C6H13
x
(2F2F)12
108
Scheme 4.1 Synthetic reagents and conditions: (i) NBS, benzoyl peroxide, CCl4, irradiation, reflux, 4h; (ii) Na, MeOH, 12h; (iii) n-C6H13Br, 50% NaOH, Bu4NBr, 80 oC, 24h; (iv) THF, BuLi, -78 oC, 2h, then trimethylborate to r.t.; (v) 1,3-propanediol, toluene, reflux, 12h; (vi) Pd(PPh3)4 (5% mole), toluene/2M Na2CO3 , 100 oC, 48h; (vii) HBr /CHCl3, 24h; (viii) Thiourea, MeOH , reflux, 2h, then NaOH reflux, 2h; (ix) KOH, Ethanol/Hexane, N2, 24h; (x) P(OMe)3, Uv irradiation, 24h.
4.3.2 Synthesis of (4,7,12,15)-Tetra(N-n-hexylcarbazole -3 -yl) [2,2]paracyclophane
(2C2C) and (4,7)-Bis(9,9-di-n-hexyl-fluorene-2-yl)-(12,15)-bis(N-n-
hexylcarbazole -3 -yl) [2,2]paracyclophane (2F2C)
NH
NH
i iiBr Br
NC6H13
13 14 15
BO
Oiii
NC6H13
16
109
+Br
Br
OMe
MeO
OMe
MeO
iv
1716
NC6H13
N C6H13
7
NC6H13
BO
O
+Br
Br
OMe
MeO
OMe
MeO
iv
1716
NC6H13
N C6H13
3
NC6H13
BO
O
2
v
Br
Br
NC6H13
N C6H13
SH
HS
NC6H13
N C6H13vi
18 19
110
S
S
18 + 19
20 (DiS2C2C)
viiN C6H13
NC6H13
NC6H13
NC6H13
21 (2C2C)
N C6H13
NC6H13
NC6H13
NC6H13
viii
Br
Br
NC6H13
N C H
HSC6H13
6 13C6H13
18
+SH
C H6 13
C H
vii
6 13
10
111
S
S
22 (DiS2F2C)
NC6H13
NC6H13
C6H13
C6H13
C6H13
C6H13
viii
23 (2F2C)
NC6H13
NC6H13
C6H13
C6H13
C6H13
C6H13
Scheme 4.2 Synthetic reagents and conditions: (i) NBS, DMF, reflux, 12h; (ii) n- C6H13Br, KOH, MeOH, 50 oC, 24h; (iii) THF, BuLi, -78 oC, 2h, then 2- isopropoxy-4,4,5,5-tetramethyl 1,3,2- dioxaboralane to r.t.; (iv) Pd(PPh3)4
(5% mole), toluene/2M Na2CO3 ,100 oC, 48h; (v) HBr gas, CHCl3, 24h; (vi) Thiourea, MeOH, reflux, 2h, and then NaOH reflux, 2h; (vii) KOH, Ethanol/Hexane, N2, 24h; (viii) P(OMe)3, UV irradiation, 24h.
4.3.3 Synthesis of (4,7)-Bis(9,9-di-n-hexyl-fluoren-2-yl)-(12,15)-bis(thiophene-2-yl)
[2,2]paracyclophane (2F2T) and (4,7)-Bis(N-n-hexylcarbazole-3-yl)-(12,15)-
bis(thiophene-2-yl) [2,2]paracyclophane (2C2T)
S S B(OH)2i
2524
112
Br
Br
OMe
MeO
7
+
OMe
MeOS
S
Br
S
S
Br
ii iii
26 27
S B(OH)2
25
SH
HSC6H13
C6H13
C6H13C6H13
10
+
Br
S
S
Br
iv
27
.
28 (DiS2F2T)
C6H13
C6H13
C6H13
C6H13
S
S v
29 (2F2T)
C6H13
C6H13
C6H13
C6H13
S
S
S
S .
113
SH
HS
NC6H13
N C6H13
19
+
Br
S
S
Br
27
iv.
30 (DiS2C2T)
S
S
NC6H13
NC6H13
S
S
S
S
NC6H13
NC6H13
31 (2C2T)
v .
Scheme 4.3 Synthetic reagents and conditions: (i) THF, BuLi, -78 oC, 2h, then trimethylborate to r.t.; (ii) (PPh3)4Pd (5% mole), toluene/2M Na2CO3 , 100 oC, 48h; (iii) HBr gas, CHCl3, 24h; (iv) KOH, Ethanol/Hexane, N2, 24h; (v) KOH, Ethanol/Hexane, N2, 24h; (v) P(OMe)3, Uv irradiation, 24h. 4.4 Results and Discussion
4.4.1 Synthesis methodology
Suzuki coupling reaction was chosen to attach the functional R groups on the benzene
rings. There were two key steps in the whole synthesis route.
First, methoxy groups were chosen to protect –CH2Br group in the Suzuki coupling
reaction. By this method, we can freely att h different functional groups on the 2, 5-ac
114
position of the benzene with no forming of complicated methyl group bromination
byproducts. (Figure 4.12)
Br
Br
Br
Br
Br
Br
OMe
Br
Br
MeO
OMe
R1
R1
MeO
Br
R1ii. Na/MeOH iii. Suzuki iv. HBr
R1
Br
R1
R1
R1
R1
Br
Br
i.
l4
v. Suzuki coupling
vi. NBS/CCl4
NBS/CC coupling
Route 1
Complicated bromination byproductscaused by the alkyl groups on R1
Route 2
Fig. 4.12 Protection and deprotection of -CH2Br group on the benzene ring
As shown in Figure 4.26, Route 2 can not be processed because of the complicated
bromination byproducts caused by the alkyl groups on R1. In Route 1, sodium methoxide
was chosen to protect –CH2Br group and HBr gas was chosen as the deprotecting reagent.
Although there were two more steps than Route 2, the yield of Route 1 was still
satisfactory because step ii and step iv were almost quantitative reactions and no silica gel
column purification were needed if the precursors in these two reactions were pure. It
should be noted that using HBr gas in chloroform system as deprotecting reagent was
much better than traditional HBr water solution. The latter had only about 30% yield and
any byproducts. The separation also caused much efforts because the –CH2Br group
as active in silica gel column. In summary, although two more steps were used to
protect and deprotect the benzyl bromide group, the whole yield of route 1 was still
determined by the Suzuki coupling reaction of step iii.
m
w
115
Second, after the high dilution coupling reaction, How to remove two sulphur atoms
from [3.3] dithiaparacyclophane to form [2.2] paracyclophane was a big challenge in this
synthesis route. By our knowledge, there were four normal ways to obtain the final
products from dithioether compounds as shown in Figure 4.13.
SO2 SO2
350-4000C
High vaccum
S S
H3CS
SCH3
CH2Cl2/CBr2CF2
KOH/Al2O3, 00C
LDACH
3 IRaney Nickle
H2/Pd(CH
3 O)2 CH +BF
4 -NaH, THF
H 2O 2
H 2
Pd/
C
Route 1
Route 2
Route 3
Route 4
P(OM
e)3 /Uv
reactor
Fig. 4.13 Synthesis of [2.2]paracyclophanes from [3.3]dithiaparacyclophanes precursors
The pyrolytic method in Route 1 needs a high temperature and very high vacuum
degree reaction instrument which can not be equipped by most of the labs. We tried
utes 2, 3 and 4. Although Ramberg Backlund reaction in Route 2 was very simple, but
omplete the whole reaction and the overall yield is very low (0.3%).
ro
no final products was obtained maybe due to the huge bulky substitution groups’
affection on the form of intermediate. The Stevens rearrangement method in Route 3
needs 3 or 4 steps to c
116
There was only a trace final product which can be detected by mass spectrum. This may
n groups. Then we had to try
btained in local area.
also be caused by the huge steric hindrance of the substitutio
Route 4. This route gave a surprising good yield (>75%) of final products although the
reaction solvent P(OMe)3 was very smelly and not easy to be o
4.4.2 NMR spectra
117
118
0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.5f1 (ppm)
0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0
DiS2F2C
Hb1 Hb2Ha1
Ha2N-CH2-
2F2C
N-CH2-
Ha1 Ha2 Hb1 Hb2
8.5f1 (ppm)
1.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0f1 (ppm)
1.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0f1 (ppm)
DiS2C2T
Ha1 Hb1Ha2
Hb2
N-CH2-
2C2T
Ha1 Ha2 Hb1 Hb2
N-CH2-
impurity
Fig. 4.14 NMR spectrum of five target [2,2]paracyclophanes
119
In dithiaparacyclophanes, the protons of CH2 groups on the cyclophane core bridge can
ot rotate freely because of the ring bridges limitation. The two protons of same bridge
H2 had different chemical environment and can be split by each other. So there are two
ouble splitting peaks at the range of 3.5-4.5 ppm. After removing 2 sulphur atoms from
ridges, [3.3]dithioparacyclophane was changed to [2.2]paracyclophane. All the bridge
H2 protons NMR peaks are removed to the high field and become multiple peaks due to
their splitting by protons on the neighbor CH2 group. Compared five target
[2.2]paracyclophanes with their [3.3]dithiaparacyclophanes precursors, we can see that
all the protons on the final products cores bridges have reduced chemical shifts values
and moved to high fields because of the absence of election-withdrawing sulphur atoms.
These high field chemical shifts and multiple peaks are clear proofs of the forming of
[2.2]paracyclophanes cores.
n
C
d
b
C
R1
R1
R2
R2R1
R2
S
SR1
R2 Hb2
Hb1
Hb2
Hb1
Ha1 Ha2Ha1 Ha2
. .
Fig. 4.15 The different protons on cyclophane core bridge -CH2 groups
4.4.3 MALDI-TOF mass spectrum
All the MALDI-TOF mass spectra of dithia[3.3]paracyclophanes are showed as
follows.
120
77
.27
8
76
9.7
06
15
40
.29
1
61
4.9
40
68
4.8
07
44
5.3
99
52
9.7
78
15
96
.28
9
81
3.0
81
82
5.3
52
14
56
.07
6
0
1000
2000
3000
4000
5000Inte
ns.
[a.u
.]
0 500 1000 1500 2000 2500
m/z
MALDI-TOF mass spectrum of 2F2F
77
.27
9
60
2.6
26
12
06
.91
6
0
500
1000
1500
2000
Inte
ns.
[a.u
.]
0 500 1000 1500 2000 2500
m/z
MALDI-TOF mass spectrum of 2C2C
121
77
.27
9
13
73
.90
7
55
1.2
65
68
5.9
05
79
9.9
52
61
5.9
21
10
44
.49
4
14
29
.50
9
0
1000
2000
3000
Inte
ns.
[a.u
.]
0 500 1000 1500 2000 2500
m/z
MALDI-TOF mass spectrum of 2F2C
77
.27
7
10
38
.57
4
76
9.1
35
0
500
1000
1500
2000
Inte
ns.
[a.u
.]
0 500 1000 1500 2000 2500
m/z
MALDI-TOF mass spectrum of 2F2T
122
77
.27
9
60
1.8
66
87
1.6
55
71
0.7
63
0
250
500
750
1000
1250
Int
s. [a
.u.]
en
0 500 1000 1500 2000 2500
m/z
MALDI-TOF mass spectrum of 2C2T
Fig. 4.16 MALDI-TOF mass spectrum of all final [2.2]paracyclophanes
Compound 2F2F, 2C2C, 2F2C, 2F2T and 2C2T have MALDI-TOF mass spectra at
1540.291, 1206.916, 1373.907, 1038.574 and 871.655. They all have good
correspondence with their molecular weights.
All the spectroscopic properties of the target [2.2]paracyclophanes molecules were
e optical properties are summarized in Table 4.1.
4.4.4 Optical Properties (UV and PL)
measured in chloroform solution. Th
The representative UV-vis absorption and photoluminescence (PL) are shown in Figure
4.17-21.
123
250 300 350 400 450 500 550 6000.0
0.2
0.4
0.6
0.8
1.0
1.2
0
200
400
600
800
1000
1200
Ab
sorb
an
ce (
No
rma
lize
d)
Wavelength (nm)
DiS2F2F UV 2F2F UV DiS2F2F PL 2F2F PL
PL
Inten
sity (a.u.)
Fig. 4.17 The UV-vis absorption spectra and photoluminescence spectra of DiS2F2F(11) and 2F2F(12) measured from their chloroform solution at room temperature As depicted in Figure 4.17, com rption in 318 nm
(with a shoulder at 279nm) and emission in 382 nm. Compound 2F2F(12) has a UV
absorption in 337 nm (with a sub-peak at 271 nm) and emission in 417 nm. 2F2F(12) has
an 81 nm Stokes shift. Compared with DiS2F2F(11), 2F2F(12) exhibits a 19nm red shift
in UV absorption and 35 nm red shift in PL emission. Its large red shift in PL shows that
2F2F(12) molecule through space interaction was strongly enhanced by removing the
two sulfur atoms from the Dithioparacyclophane core in DiS2F2F(11). In 2F2F(12), the
two benzene rings in the cyclophane were co-facially in close proximity. The [2.2]-
paracyclophane served as a locus of 2 layer’s chromophores contact. By the effective π-π
electron delocalization, 2F2F(12) shows strong combining properties of two layers’
chromophores. This is one of the most important purposes of this synthesis work.
pound DiS2F2F(11) has a Uv abso
124
250 300 350 400 450 500 550 6000.0
0.2
0.4
0.6
0.8
1.0
1.2
0
200
400
600
800
1000
1200
Ab
sorb
anc
e (N
orm
aliz
ed
)
Wavelength (nm)
DiS2C2C UV 2C2C UV DiS2C2C PL 2C2C PL
PL
Inten
sity (a
.u.)
Fig. 4.18 The UV-vis absorption spectra and photoluminescence spectra of DiS2C2C(20) and 2C2C(21) measured from their chloroform solution at room temperature
As depicted in Figure 4.18, compound DiS2C2C(20) has a UV absorption in 301 nm
and emission in 371 nm. Compound 2C2C(21) has a UV absorption in 304 nm (with a
sub-peak at 329 nm) and emission in 419 nm. 2C2C(21) has a 116 nm Stokes shift.
Compared with DiS2C2C(20), 2C2C(21) exhibits a 3 nm red shift in UV absorption and
48 nm red shift in PL emission. Its large red shift in PL shows that [2,2]-paracyclophane
(pCp) core in 2C2C(21) molecule plays a much more important role in through space
interaction than Dithia[3,3]paracyclophane core in DiS2C2C(20).
125
250 300 350 400 450 500 550 6000.0
0.2
0.4
0.6
0.8
1.0
1.2
0
200
400
600
800
1000
1200
Ab
sorb
ance
(N
orm
aliz
ed)
Wavelength (nm)
DiS2F2C UV 2F2C UV DiS2F2C PL 2F2C PL P
L In
tens
ity (a.u
.)
Fig. 4.19 The UV-vis absorption spectra and photoluminescence spectra of DiS2F2C(22) and 2F2C(23) measured from their chloroform solution at room temperature. As depicted in Figure V absorption in 302 nm
UV
sion. Its large red shift in PL shows that
.2]-paracyclophane(pCp) core in 2F2C(23) molecule plays a much more important role
.3]paracyclophane core in DiS2F2C(22).
4.19, compound DiS2F2C(22) has a U
(with a shoulder at 318 nm) and emission in 373 nm. Compound 2F2C(23) has a
absorption in 305 nm (with a sub-peak at 332 nm) and emission in 416 nm. 2F2C(23) has
a 111 nm Stokes shift. Compared with DiS2F2C(22), 2F2C(23) exhibits a 3 nm red shift
in UV absorption and 42 nm red shift in PL emis
[2
in through space interaction than Dithia[3
126
250 300 350 400 450 500 550 6000.0
0.2
0.4
0.6
0.8
1.0
1.2
0
200
400
600
800
1000
1200
Ab
sorb
an
ce (
No
rmal
ized
)
Wavelength (nm)
DiS2F2T UV 2F2T UV DiS2F2T PL 2F2T PL P
L In
tensity
(a.u.)
Fig. 4.20 The UV-vis absorption spectra and photoluminescence spectra of DiS2F2T(28) and 2F2T(29) measured from their chloroform solution at room temperature As depicted in Figure 4.20, compound DiS2F2T(28) has a UV absorption in 303 nm
(with a shoulder at 328 nm) and emission in 368 nm. Compound 2F2T(29) has a UV
absorption in 319 nm and emission in 415 nm. 2F2T(29) has a 97 nm Stokes shift.
Compared with DiS2F2T(28), 2F2T(29) exhibits a 15 nm red shift in UV absorption and
47 nm red shift in PL emission. Its large red shift in PL shows that [2,2]-paracyclophane
(pCp) core in 2F2T(29) molecule plays a much more important role in through space
interaction than Dithia[3,3]paracyclophane core in DiS2F2T(28).
127
250 300 350 400 450 500 550 6000.0
0.2
0.4
0.6
0.8
1.0
1.2
0
200
400
600
800
1000
1200
Ab
sorb
an
ce (
No
rma
lize
d)
Wavelength (nm)
DiS2C2T UV 2C2T UV DiS2C2T PL 2C2T PL
PL
Inten
sity (a
.u.)
Fig. 4.21 The UV-vis absorption spectra and photoluminescence spectra of DiS2C2T(30) and 2C2T(31) measured from their chloroform solution at room temperature
In conclusion, compared with their Dithia[3,3]paracyclophane core precursor
ompounds, all final [2,2]paracyclophane substituted compounds have large obvious red
ifts(from 35 to 50 nm) in their PL spectrum. These red shifts also make them to have
rge Stokes shifts (from 81 to 127nm). Compound 2C2T has a biggest Stokes shift (127
m) and biggest red shift in PL spectrum compared with its precursor (50 nm), but it has
no red shift in Uv absorption compared with its precursor. For compound 2F2F, it is very
As depicted in Figure 4.21, compound DiS2C2T(30) has a UV absorption in 302 nm
and emission in 379 nm. Compound 2C2T(31) has a UV absorption in 302 nm (with a
sub-peak at 338 nm) and emission in 429 nm. 2C2T(31) has a 127 nm Stokes shift.
Compared with DiS2C2T(30), 2C2T(31) exhibits only no red shift in UV absorption and
50 nm red shift in PL emission. Its large red shift in PL shows that [2,2]-paracyclophane
(pCp) core in 2C2T(31) molecule plays a much more important role in through space
interaction than Dithia[3,3]paracyclophane core in DiS2C2T.
c
sh
la
n
128
interesting that it has a smallest Stokes shift (81 nm) and smallest red shift in PL
spectrum compared with its precursor (35 nm), but it has a biggest red shift in Uv
absorption compared with its precursor (19 nm).
By removing the two sulfur atoms from the precursor Dithia[3,3]paracyclophane core ,
the nearer two benzene rings co-facial proximity forms a strong π-π delocalization. This
strong π-π delocalization performs dominant effect on their PL and Uv behavior.
Table 4.1 The optical data of [2.2]paracyclophanes and their precursors [3.3]dithioparacyclophane in chloroform solution
Solution λmax(nm)a Eg(eV)b PL Efficiency (%)compound
Abs. Em
DiS2F2F 318 (279) 382 3.52
2F2F 337 (272) 417 3.28 78%
DiS2C2C 301 371 3.87
2C2C 304 (329) 419 3.77 45%
DiS2F2C 302 (318) 373 3.43
2F2C 305 (332) 3.31 63% 416
DiS2F2T 303 (328) 368 3.78
2F2T 319 415 3.49 67%
DiS2C2T 302 379 3.78
2C2T 302 (338) 429 3.66 55%
a. The data in the parentheses are the wavelength of shoulders and sub-peaks; b. Eg stands for the band gap energy estimated from the onset wavelength of the optical absorption.
129
4.4.5 Electrochemical Properties
The electrochemical behavior of final substituted cyclophanes and their
dithia[3.3]paracyclophane precursors was investigated by the Cyclic Voltammetry (CV).
The CV was performed in a solution of Bu4NClO4 (0.10M) in chloroform at a scan of 50
mV/s at room temperature under the protection of argon. A platinum electrode was used
as the working electrode. A Pt wire was used as the counter electrode and an Ag/AgNO3
electrode was used as the reference electrode. The corresponding data are summarized in
Figure 4.22-26 and Table 4.2.
-2 -1 0 1 2-6
-4
-2
0
2
8
4
6
I (m
A)
(n
orm
.)
DiS2F2F
E (V vs SCE)
-2 -1 0 1 2-10
-5
0
5
15
10
I (m
A)
(n
Fig. 4.22 The cyclic voltammograms of DiS2F2F(11) and 2F2F(12)
8
o
r
E (V vs SCE)
2F2F
m.)
-2 -1 0 1 2
-6
-4
-2
0
2
4
6
10
DiS2C2C6
8
-1 0 1 2-8
-6
-4
-2
0
2
4
2C2C
I (m
A)
(no
rm.)
E (V vs SCE)
I (m
A)
(no
rm.)
E (V vs SCE)
Fig. 4.23 The cyclic voltammograms of DiS2C2C(20) and 2C2C(21)
130
-2 -1 0 1 2-6
-4
-2
0
2
4
6
8
I (m
A)
(no
rm.)
E (V vs SCE)
DiS2F2C
-2 -1 0 1 2
-4
-2
0
2
4
I (m
A)
(no
rm.)
E (V vs SCE)
2F2C
Fig. 4.24 The cyclic voltammograms of DiS2F2C(22) and 2F2C(23)
0 1 2-2
0
2
6
4
I (m
A
E (V vs SCE)
-2 -1 0 1 2-6
-4
0
) (
DiS2F2T
no
rm.)
2
-2
6
8
4
I (m
A
E (V vs SCE)
8
10
) (
2F2T
Fig. 4.25 The cyclic voltammograms of DiS2F2T(28) and 2F2T(29)
no
rm.)
0 1-2
0
4
6
2
2
IA
) (n
orm
E (V vs SCE)
-2
0
2
-2 -1 0 1 2
4
6
(m
.)
DiS2C2T
I (m
(n
orm
.)
E (V vs SCE)
Fig. 4.26 The cyclic voltammograms of DiS2C2T(30) and 2C2T(31)
A)
2C2T
131
Table 4. 2 The electrochemical data of [2.2]paracyclophanes and their
p-doping (V)
[3,3]dithioparacyclophane precursors in chloroform solution
Energy levels(eV) compound
Eonset Epa Epc HOMO LUMO Eg
DiS2F2F 1.21 1.9 1.40 -5.61 -2.09 3.52
2F2F 0.84 1.04 0.87 -5.24 -1.96 3.28
DiS2C2C 0.80 2.01 1.41 -5.20 -1.33 3.87
2C2C 0.52 1.69 ---- -4.92 -1.15 3.77
DiS2F2C 1.11 1.86 1.53 -5.51 -2.08 3.43
2F2C 0.64 1.49 1.10 -5.04 -1.73 3.31
DiS2F2T 0.88 1.60 0.80 -5.28 -1.50a 3.78
2F2T 0.74 1.80 1.51 -5.14 -1.65 .49 3
DiS2C2T 0.78 1.39 0.82 -5.18 -1.40a 3.78
2C2T 0.71 1.30 0.71 -5.11 -1.45 .66 3
a. LUMO energy calculated by nd HOMO e level
e [2. phane were substituted by electron-donating group such as
thiophene and carbazole, the band gaps were enlarged, which agreed with the spectral
heir hig occupied mole orbital (HOM d the lowest u ccupied
molecular orbital (LUMO) energies had shifted to a higher energy level. These obvious
levels via
tution on the cyclophane core. By changing the substituted chromophores,
the final compounds can have a 0.32 eV change (-5.24 eV to -4.92 eV) in HOMO orbital
level was Eg a nergy
When th 2]paracyclo
blue shift. T hest cular O) an no
differences had well illustrated the adjustable HOMO and LUMO energy
different substi
132
and 0.81 eV change in LUMO orbital (-1.96 eV to -1.15 eV) in the meantime the blue
reaction and UV irradiation reaction, give a guarantee for
the satisfactory yield of whole synthesis route.
Efficient blue light emission, good solubility in common organic solvents had been
demonstrated in all of the five compounds. The optical and electrochemical properties all
exhibited dependence on the changes of different substituted chromophores on the
[2.2]paracyclophane core.
The band gaps of five compounds were varied between 3.28 eV to 3.77 eV.
Modification of the substitution groups on the [2.2]paracyclophane core enabled the
akes the synthesis
route very useful to obtain different [2.2] paracyclophanes derivatives which can be used
in different applications areas such as asymmetric reaction, OLED and NLO materials.
emission are maintained. These changes can still be enhanced by attaching the electron-
withdrawing groups on the cyclophanes core.
4.5 Conclusion
A concise and novel synthesis route was successfully established and five tetra-
substituted [2.2]paracyclophanes were obtained in high yields. Two key step reactions,
which are HBr gas deprotecting
tuning of HOMO and LUMO energy levels. This freely modification m
133
Reference
1. Cram, D. J.; Abeall, J. J. Am. Chem. Soc. 1955, 77, 1179.
2. Shultz, J.; Vögtle, F. Top. Curr. Chem. 1994, 172, 42.
3. Vögtle, F. Cyclophane chemistry: synthesis, structures and reactions. ; Wiley
New York, 1993.
4. Diederich, F. Cyclophanes, UK: Royal Society of Chemistry,Cambridge; 1991.
istry., Weinheim,
Germany: Wiley-VCH; 2004.
6. Morisaki, Y.; Chujo, Y. Prog. Polym. Sci. 2008, 33, 346.
7. Guyard, L.; Audebert, P. Electrochem. Commun. 2001, 3, 164.
8. Guyard, L.; Audebert, P.; Dolbier, J., WR.; Duan, J.-X. J. Electroanal. Chem.
2002, 537, 189.
9. Salhi, F.; Lee, B.; Metz, C.; Bottomley, L.; Collard, D. Org. Lett. 2002, 4, 3195.
11. Morisaki, Y.; Chujo, Y. Angew. Chem. Int. Ed. 2006, 45, 6430.
12. Morisaki, Y.; Chujo, Y. Macromolecules 2002, 35, 587.
13. Morisaki, Y.; Ishida, T.; Tanaka, H.; Chujo, Y. J. Polym. Sci., Part A: Polym.
Chem. 2004, 42, 5891.
14. Morisaki, Y.; Wada, N.; Chujo, Y. Polymer 2005, 46, 5884.
15. Morisaki, Y.; Wada, N.; Chujo, Y. Polym. Bull. 2005, 53, 73.
16. Morisaki, Y.; Chujo, Y. Macromolecules 2003, 36, 9319.
5. Cleiter, R.; Hopf, H., editors. Modern cyclophane chem
10. Salhi, F.; Collard, D. Adv. Mater. 2003, 15, 81.
17. Morisaki, Y.; Chujo, Y. Chem. Lett. 2002, 194.
134
18. Morisaki, Y.; Ishida, T.; Chujo, Y. Macromolecules 2002, 35, 7872.
19. Morisaki, Y.; Chujo, Y. Macromolecules 2004, 37, 4099.
isaki, Y.; Ch em. Soc. Jpn. 2005, 7
21. Tohda, Y.; Sonogashira, K.; Hagihara, N. Syn 7, 7
ogas Sonogashira alkyne synthesis. In: Negishi E, editor. Handbook of
ganop um che for org synthes w Yor y-VCH 2,
.
23 izorok Mori, K ki, A. Bull. Chem. Soc. Jpn. 1971 81.
k, R olley, J . J. Org. Chem. 1972 320.
25 ase, S Meijer
nes— eck re . In: D ch F, S J, ed etal-c d
oss-co reacti ew Yor 8. p. 99–166.
aura uzuki, Chem. S hem. C n. 197
27 iyaura uzuki, em. Re 5, 95, 2
9. Wang, W. L.; Xu, J. W.; Lai, Y. H.; Wang, F. K. Macromolecules 2004, 37, 3546.
20. Mor ujo, Y. Bull. Ch 8, 288.
thesis 197 77.
22. Son hira, K.
or alladi mistry anic is., Ne k: Wile ; 200
493
. M i, T.; .; Oza , 44, 5
24. Hec . F.; N ., JP. , 37, 2
. Br .; de e, A. Palladium-catalyzed coupling of organyl halides to
alke the H action iederi tang P itors. M atalyze
cr upling on., N k: Wiley-VCH; 199
26. Miy , N.; S A. J. oc., C ommu 9, 866.
. M , N.; S A. Ch v. 199 457.
28. Wang, W. L.; Xu, J. W.; Lai, Y. H. Org. Lett. 2003, 5, 2765.
2
30. Wang, W. L.; Xu, J. W.; Sun, Z.; Zhang, X. H.; Lu, Y.; Lai, Y. H.
Macromolecules 2006, 39, 7277.
31. Wang, W. L.; Xu, J. W.; Lai, Y. H. J. Polym. Sci., Part A: Polym. Chem. 2006, 44,
4154.
32. Cram, D. J.; Allinger, N. J. Am. Chem. Soc. 1955, 77, 6289.
33. Rosenfeld, S. M.; Keehn, P. M. Cyclophanes; Academic Press: New York, 1983;
Vol. 1 and 2.
135
34. Diederich, F. N. Cyclophanes; Royal Society of Chemistry: Cambridge, 1991.
35. Vögtle, F. Cyclophane Chemistry; Wiley: New York, 1993.
36. Gareth, J. R. Org. Biomol. Chem. 2008, 6, 1527.
7. Pye, P. J.; Rossen, K.; Reamer, R. A.; Volante, R. P.; Reider, P. J. Tetrahedron
, 4441.
g. Lett. 2001, 3, 287.
8. Chromophores studied in this manner include: (a) phenanthrenophane:Schweitzer,
D. H., K. H.; Haenel, M. Chem. Phys. 1978, 29, 181.(b) Anthracenophane:
Ishikawa,S.; Nakamura, J.; Iwata, S.; Sumitami, M.; Nagakura, S.; Sakata, Y.;
Misumi, S. Bull. Chem. Soc. Jpn. 1979, 52, 1346. (c) Fluorenophane: Haenel, M.
W. Tetrahedron Lett. 1976, 36, 3121. (d) Colpa, J. P.; Hausser, K. H.; Schweitzer,
3
Lett. 1998, 39
38. Rossen, K.; Pye, P. J.; Maliakal, A.; Volante, R. P. J. Org. Chem. 1997, 62, 6462.
39. Pye, P. J.; Rossen, K.; Reamer, R. A.; Tsou, N. N.; Volante, R. P.; Reider, P. J. J.
Am. Chem. Soc. 1997, 119, 6207.
40. Tanji, S.; Ohno, A.; Sato, I.; Soai, K. Or
41. Sato, J.; Ohno, A.; Aoyama, Y.; Kasahara, T.; Soai, K. Org. Biomol. Chem. 2003,
344.
42. Masterson, D. S.; Hobbs, T. L.; Glatzhofer, D. T. J. Mol. Cat. A: Chem. 1999, 145,
75.
43. Masterson, D. S.; Glatzhofer, D. T. J. Mol. Cat. A: Chem. 2000, 161, 65.
44. Bolm, C.; Kühn, T. Synlett 2000, 6, 899.
45. Susan, E. G.; Jamie, D. K. Org. Biomol. Chem. 2003, 1, 1256.
46. Zhang, T. Z.; Dai, L. X.; Hou, X. L. Tetrahedron: Asymmetry 2007, 18, 251.
47. Bazan, G. C. J. Org. Chem. 2007, 72, 8615.
4
136
D. Chem. Phys. 1978, 29, 187. (e) Pyrenophane and several isomers of
naphthalenophane: Haenel, M.; Staab, H. A. Chem. Ber. 1973, 106, 2190; Otsubo,
Chem. Soc. Jpn. 1977,
undahl, M.; Wennerstro¨m,
riguchi, T.; Sakata, K. J. Org. Chem. 1999, 64, 7246. (g)
J.;
49. reactions (a) Grieving, H. H., H.; Jones, P. G.;
J. Chem. Soc., Chem.
ishimura, J. Chem.
Bouass-Laurent, J. Liebigs. Ann. 1995, 11, 1949.
,
. Am. Chem. Soc.
m. Soc. 1998, 120, 9188.
.
ss, J. J. Am. Chem.
nyak, V. Science 1997, 277, 781.
T.; Mizogami, S.; Osaka, N.; Sakata, Y.; Misumi, S. Bull.
50, 1858. (f) Stilbenophanes: Anger, I.; Sandros, K.; S
O. J. Phys. Chem. 1993, 97, 1920; Tsuge, A.; Nishimoto, T.; Uchida, T.;
Yasutake, M.; Mo
Phthalocyanines: de la Escosura, A.; Claessens, C. G.; Ledoux-Rak, I.; Zyss,
Martinez-Dias, M. V.; Torres, T. J. Porphyrins Phthalocyanines 2005, 9, 788.
For studies of cycloaddition
Bubenitscheck, P.; Desvergne, J. P.; Bouass-Laurent,
Commun. 1994, 9, 1075. (b) Okada, Y.; Ishii, F.; Akiyama, I.; N
Lett. 1992, 8, 1579. (c) Grieving, H.; Hopf, H.; Jones, P. G.; Bubenitscheck, P.;
Desvergne, J. P.;
50. Gleiter, R. H., H. Modern Cyclophane Chemistry; Wiley-VCH: Weinheim
Germany, 2004.
51. Oldham, W. J.; Miao, Y.-J.; Lachicotte, R. J.; Bazan, G. C. J
1998, 120, 419.
52. Bazan, G. C.; Oldham, W. J.; Lachicotte, R. J.; Tretiak, S.; Chernyak, V.;
Mukamel, S. J. Am. Che
53. Yaliraki, S. N.; Ratner, M. A. J. Chem. Phys. 1998, 109, 5036
54. Bartholomew, G. P.; Ledoux, I.; Mukamel, S.; Bazan, G. C.; Zy
Soc. 2002, 124, 13480.
55. Mukamel, S.; Tretiak, S.; Wagersreiter, T.; Cher
137
56. Tretiak, S.; Chernyak, V.; Mukamel, S. Chem. Phys. Lett. 1996, 259, 55.
6, 105, 8914.
ich, J. E.; Erskine,
hotochem.
62. arson, J. R.;
Phys. 1996, 1041. .
J. C.; Dillard, A. G.;
In Materials Researcg Society Symposium Proceedings: Materials for
agan, D., Lewis, K.,
67. kamura, O.; Kawata, S. Opt. Lett. 1997, 22, 132.
57. Tretiak, S.; Chernyak, V.; Mukamel, S. J. Chem. Phys. 199
58. Strickler, J. H.; Webb, W. W. Opt. Commun. 1991, 16, 1780.
59. Cumpston, B. H.; Ananthavel, S. P.; Barlow, S. D., D. L.; Ehrl
L. L.; Heikal, A. A.; Kuebler, S. M.; Lee, I.-Y. S.; McCord-Maughon, D.; Qin, J.;
Ro¨ckel, H.; Rumi, M.; Wu, X.-L.; Marder, S. R.; Perry, J. W. Nature 1999, 398,
51.
60. Stiel, H.; Teuchner, K.; Paul, A.; Freyer, W.; Leupold, D.; J. P
Photobiol. A 1994, 289.
61. Bhawalkar, J. D.; Kumar, N. D.; Zhao, C.-F.; Prasad, P. N.; J. Clin. Laser Surg.
1997, 201.
Fleitz, P. A.; Brant, M. C.; Sutherland, R. L.; Strohkendl, F. P.; L
Dalton, L. R. Proc. SPIE Int. Soc. Opt. Eng. 1998, 91, 3472.
63. Bhawalkar, J. D.; He, G. S.; Prasad, P. N.; Rep. Prog.
64. He, G. S.; Xu, G. C.; Prasad, P. N.; Reinhardt, B. A.; Bhatt,
Opt. Lett. 1995, 435.
65. Ehrlich, J. E.; Wu, X.-L.; Lee, L.-Y.; Hu, Z.-Y.; Röckel, H.; Marder, S. R.; Perry,
J. W. Opt. Lett. 1997, 22, 1843.
66. Ehrlich, J. E.; Wu, X.-L.; Lee, I.-Y. S.; Hu, Z.-Y.; Röckel, H.; Marder, S. R.; Perry,
J. W.
Optical Limiting II, Sutherland, R., Patcher, R., Hood, P., H
Perry, J. W., Eds.; MRS: Pittsburgh, PA, 1997, Vol. 479, 9-15.
Maruo, S.; Na
138
68. Zhou, W. H.; Kuebler, S. M.; Braun, K. L.; Yu, T. Y.; Cammack, J. K.; Ober, C.
T.; Wenseleers, W.; Alain, V.;
72. mi, T.; Matsuo, S.; Misawa, H. Appl. Phys. A
74. . S.; Strickler, J. H.; Harrell, W. R.; Webb, W. W. Proc. SPIE Int. Soc. Opt.
75. ta, M.; Beljonne, D.; Bredas, J.-L.; Ehrlich, J. E.; Fu, J.-Y.; Heikal, A. A.;
.; Perry,
am, G.; Webb, W. W.; Wu, X.-L.; Xu, C.
r, J.; Sankey, O. F.; Moore, A. L.;
78.
79.
80.
K.; Perry, J. W.; Marder, S. R. Science 2002, 296, 1106.
69. Stellacci, F.; Bauer, C. A.; Meyer-Friedrichsen,
Kuebler, S. M.; Pond, S. J. K.; Zhang, Y. D.; Marder, S. R.; Perry, J. W. Adv.
Mater. 2002, 14, 194.
70. Sun, H. B.; Tanaka, T.; Takada, K.; Kawata, S. Appl. Phys. Lett. 2001, 79, 1411.
71. Kawata, S.; Sun, H. B.; Tanaka, T.; Takada, K. Nature 2001, 412, 697.
Miwa, M.; Juodkazis, S.; Kawaka
2001, 73, 561.
73. Strickler, J. H.; Webb, W. W. Proc. SPIE Int.Soc. Opt. Eng. 1990, 1398, 107.
Wu, E
Eng. 1992, 1674, 776.
Albo
Hess, S. E.; Kogej, T.; Levin, M. D.; Marder, S. R.; McCord-Maughon, D
J. W.; Ro¨ckel, H.; Rumi, M.; Subramani
Science 1998, 281, 1653.
76. Nitzan, A.; Ratner, M. A. Science 2003, 300, 1384.
77. Cui, X. D.; Primak, A.; Zarate, X.; Tomfoh
Moore, T. A.; Gust, D.; Harris, G.; Lindsay, S. M. Science 2001, 294, 571.
Kushmerick, J. G.; Naciri, J.; Yang, J. C.; Shashidhar, R. Nano Lett. 2003, 3, 897.
Xu, B.; Tao, N. J. Science 2003, 301, 1221.
Hong, J. W.; Woo, H. Y.; Liu, B.; Bazan, G. C. J. Am. Chem. Soc. 2005, 127,
7435.
139
Chapter Five
a ed oligomers are branched macromolecules that consist of linear molecular
together by a central core . Star-shaped oligomers are unique in the sense
combine the properties of the arms with that of the central core (which can have
ensional characters) and this will bring new interesting optoelectronic
Synthesis and Characterization of Hexafluorenyl Benzene
5.1 Introduction
Star-sh p
arms joined 1
that they
one to three dim
o 2
benzene3
these com
serve as potential candidates for OLED
and m rphological properties to the system. Star-shaped oligomers based on truxene and
core with oligofluorenes and thiophene arms(Figure 5.1) have been studied and
pounds are shown to have good optoelectronic properties. These systems thus
, photovoltaics and field transistors.
n
n
n
nn
n
C6H13C6
H13
C H
C3
6H
1
C6H13
C6H13
6 13
=
C6H13 C6H13
S
n
or
Fig. 5.1 Structure of star-shaped oligomers with truxene and benzene core
140
Recently, hexaarylbenzene have attracted immerse interest in the materials community;
nd these
m ar-shaped analogue.
behavio
may ex
dimensions.
“fluore fluorenes are known for their high photoluminescence
propert nt system. In addition, the nature of the side chains at the 9th position
Propyl nyl benzene.
aryl “arms” such as azulene4, pyrene5 and ferrocene6 have been attached a
syste s shows more superior properties than their trisubstituted st
For example, hexakis(azukenyl)benzene was shown to exhibit multielectron redox
r. Hexaarylbenzenes can be thought of as a “double” star-shaped system and this
plain its enhanced properties since the extra three arms add to the multitude of
We thus decide to tap on the potential of such “double” star-shaped system, using
nyl” units as the arms as
efficiency and their ease of chemical transformation. We hope to test the structure and
ies of resulta
of fluorene will be investigated to see if its length (i.e. comparing Methyl group with n-
group and n-Hexyl group) affects the formation of hexafluore
5.2 Molecular design
Br Br
R RR R R
Ri ii
R=Hex, 1aR=n-Pr, 1bR=Me, 1c
R=n-Pr, 2bR=Me, 2c
R=Hex, 2a
141
iii
R=Me, 3c
Sche e 5.1 The synthetic routes for target molecule 3c. Reagents and conditions: i. RBr, t-BuO-K+ / DMSO; ii. Trimethylsilylacetylene, Pd(PPh ) Cl CuI
m3 2 2, ,
As o different length of alkyl chains were introduced into the 9-
the fina
fluoren
reaction
he 2b and 2c in 66%, 82%, and
saving ch the
th
a coupling with the original substrate),
three steps of reaction to happen in sequence, using 1, 8- diazabicyclo[5.4.0]undec-7-
ene(DBU) as the base to remove the TMS group. Compared with triethylamine(TEA),
DBU/benzene, 80 oC, 18h; iii. Co2(CO)8 / dioxane, reflux, 24h.
utlined in Scheme 5.1,
position of fluorene. The purpose of adding an alkyl chain is to improve the solubility of
l product in organic solvent and also protect the active protons on 9-position of
e. We also want to explore how the chain lengths affect the cycloaromatization
.
T Brisbois protocol 7 was employed to obtain the 2a,
69% yields respectively. This protocol is advantageous in the sense that it allows the
of two steps reaction compared with the usual procedure (usual one is to atta
trime ylsilylacetyl group via Sonogashira coupling, follow by removal of the TMS
group by a strong base and then another Sonogashir
which save labor and improve yield and atom economy. This one pot protocol allowed all
142
1,4-diazabicyclo[2.2.2]octane (DABCO) and 1,5-Diazabicyclo[4.3.0]non-5-ene (DBN),
DBU was the best choice of base in Brisboi
indicated the amidine base was acting as a proton shuttle. In support of this determination,
orces the invocation of a DBU salt in the organic reaction mixture,8,9
s protocol .The methodology research results
the literature reinf
and DBU has been used catalytically in the nucleophilic addition of acyldiazomethanes to
aldehydes and imines.10 It can be speculated that after proceeding through the commonly
accepted cross-coupling chemistry, the silane-protected aryl-ethynylene converges with
Cu+ and a water/DBU salt, resulting in protodesilylation to yield the terminal ethynylene.
Consequently, the aryl-substituted terminal ethynylene is resubmitted to the cross-
coupling cycle, generating the bisarylethynyl product after a second pass.7
R-Br + H TMSPd(PPh3)2Cl2/CuI
3NEtR TMS
NaOH
MeOH
RBr/NEt3
Pd(PPh3)2Cl2/CuIR H R R
Fig. 5.2 Normal ways to synthesize di-R group substituted alkyne.
The final step of Scheme 5.1 involves cycloaromatization by using Co2(CO)8 as the
catalyst. Only 3c was obtained in 35% yield. The failure of obtaining the 3a and 3b may
indicate that the length of alkyl chains at the 9th position of fluorene has a significant
effect on the formation of the trimerized product. Only the smallest steric hindrance alkyl
group (methyl) can form the final product.
143
The proposed mechanism of cycloaromatization of acetylene using Co2(CO)8 is
illustrated in Scheme 2.11
Co2(CO)8R R
-2CO (OC) Co3 Co(CO)3
R RR R
-CO (OC) Co3 Co(CO)2
R R
R R
R R
(OC)3Co Co(CO)2
R
R
R
R(OC)2Co Co(CO)2
R R
R R(OC)2Co Co
RR
R R
(CO)2
R R
R R
-CO
R R
(OC)2Co Co
RR
(CO)R R
R
RR
.
2R
RR
Fig. 5.3 Proposed mechanism of Cycloaromatization by using Co2(CO)8
Other catalyst system such as Pd/C in THF, PdCl2/CuCl2/BuOH in benzene,
Pd(PPh)3Cl2 in THF and these 3 system working in microwave assisted condition were
also tested for 2a, 2b and 2c. All reactions do not obtain the final product. These results
indicate the steric bulk of the fluorenyl units and the length of side chains makes the
cycloaromatization of flouenen unit a very tough work.
5.3 Results and discussion
5.3.1 NMR spectroscopy
144
118
.16
118
.32
118
.50
119
.53
119
.65
119
.76
122
.21
122
.26
126
.50
126
.61
126
.71
130
.24
130
.51
130
.61
130
.77
26.7
526
.91
Fig. 5.4 1H and 13C spectra of target molecule 3c
145
From the 1H NMR spectrum of target molecule 3c, we can see multiple peaks at about
1.0 ppm. A double split peak at about 27 ppm in 13C spectrum is also found
corresponding to the methyl group on 9-position of fluorene. In addition, there are more
peaks in the 13C NMR spectrum as expected from a symmetrical 3c. (The expanded
aromatic region in the 13C NMR is shown in Figure 5.4). The splitting peaks show a
nonplanarity of molecule 3c. 3c is deduced to be mixture of different conformational
isomers. 3c is expected to be non-planar and a literature search indicates that such
compound tend to take on the shape of a propeller. The cycloaromatization process may
result in the random orientation of the fluorenyl units and thus result in the methyl groups
and some to the carbon atoms being chemically and magnetically non-equivalent. The
broad split signals in some aromatic regions in the 1H spectrum may suggest that 3c is a
conformational mobile system, in which there is some limited bond rotation between the
aryl-aryl single bond at room temperature.
5.3.2 MALDI-TOF mass spectrum
und to have a
omposition of C96H78 (M=1231.4254, Δ=1.80* 10-4). This provides further evidence that
A Maldi-Tof mass was performed and the target compound 3c was fo
c
compound 3c was Hexafluorenyl Benzene.
146
Fig 5.5 MALDI-TOF mass spectrum of target molecule 3c
5.3.3 Thermal Analysis (TGA and DSC)
n was
valuated by thermogravimetric analysis (TGA). 3c shows weight loss at about 220 oC in
o
The thermal stability of the final conformational mixture product 3c in nitroge
e
nitrogen (Figure 5.6). Above 460 C, there is about 30% of residue, which was produced
by charring during heating.
1200 1216 1232 1248 1264 1280
Mass (m/z)
2.3E+4
0
10
20
30
40
50
60
70
80
90
% I
nte
nsi
ty100
Voyager Spec #1=>BC=>AdvBC(32,0.5,0.1)=>NR(2.00)[BP = 1230.4, 23432]
1230.4260
1231.4254
1232.4339
1233.4327
1215.87151230.9148
1257.44681231.11611217.8774
147
100 200 300 400 500 600 700 800
0.2
0.4
0.6
0.8
1.0 3c
Wei
gh
t (%
)
Temperature (OC)
Fig 5.6 The thermogravimetric analysis (TGA) of 3c
Thermally induced phase transition behavior of 3c was also investigated with
differential scanning calorimetry (DSC) in a nitrogen atmosphere. The DSC curve of 3c
is shown in Figure 5.7. From the DSC spectrum, we can see that 3c has a glass transition
temperature (Tg) at 125oC. The relatively low glass transition temperature shows that 3c
could be a conformational mobile system.
148
0 50 100 150 200 250
7
-0.6
-0.2
-0.8
-0.
-0.5
-0.4
-0.3
-0.1
0.0
3c
H/g
)
Temperature (0C)
eat
Flo
w (
W
Fig. 5.7 The DSC trace of 3c
5.3.4 Optical Properties (UV and PL)
250 300 350 400 450 500
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0
200
400
600
800
1000
1200
Ab
sorb
1c UV 3c UV
an
(N
or
lize
dce
ma
)
Wavelength (nm)
1c PL 3c PL
PL
Inten
sity (a.u.)
Fig. 5.8 The UV-vis absorption spectra and photoluminescence spectra of 3c and 1c measured from their chloroform solution at room temperature
149
The spectroscop were measured
in CHCl3 solution. The optical properties are summarized in Table 5.1
Table 5.1 The optical data and fluorescence quantum yields (both in chloroform solutions) of compound 1c and 3c
Solution λmax(nm)a Eg(eV)b PL Efficiency (%)
ic properties of 3c and 2-Bromo-9, 9-dimethylfluorene
Compound
Abs. Em
1c 275 (309) 321 4.1 25%
3c 323 (282) 356 3.27 8%
a. The data in the parentheses are the wavelength of shoulders and sub-peaks; b. Eg stands for the band gap energy estimated from the onset wavelength of the optical absorption. As depicted in Figure 5.8, compound 3c has a Uv absorption in 323 nm (with a
shoulder at 282nm) and emission in 356 nm. Compound 3c has a 34 nm Stokes shift.
Compared with 1c, target molecule 3c has a 48nm Uv absorption and 35 nm emission
blue shift. The photoluminescence efficiency of 3c is low (8%). This was caused by the
energy lost in transformation of different conformational isomers.
or of compound 3c was investigated by the Cyclic
Voltammetry (CV). The CV was performed in a solution of Bu4NClO4 (0.10M) in
chloroform at a scan of 50 mV/s at room temperature under the protection of argon. A
platinum electrode was used as the working electrode. A Pt wire was used as the counter
electrode and an Ag/AgNO3 electrode was used as the reference electrode. The
corresponding data are summarized in Table 5.2.
5.3.5 Electrochemical Properties
The electrochemical behavi
150
0 1 2-1
0
1
2
3
4
3c
I (m
A)
(no
rm.)
E (V vs SCE)
Fig. 5.9 The cyclic voltammograms of 3c
Table 5.2 The electrochemical data of the polymers 3c
p-doping (V) Energy levels(eV) compound
aEonset Epa Epc HOMO LUMO Eg
3c 1.43 1.67 1.45 -5.83 -2.56 3.27
a. LUMO energy level was calculated by Eg and HOMO energy level
5.4 Conclusion
A convenient approach to synthesize hexafluorenyl benzene was successfully
developed. The synthesis was successful for 3c but failed for 3a and 3b. The reason for
the failure may be attributed to the increase in length of the alky chains as we move from
151
methyl to propyl to hexyl group. The increased in length of the alkyl drop may disfavor
the cycloaromatization process because there is an increased steric hindrance.
152
Reference
1. Hadjichristidis, N.; Pitsikalis, M.; Pispas, S.; Iatrou, H. Chem
. Rev. 2001, 101,
. Pei, J.; Wang, J., L.; Cao, X., Y.; Zhou, X., H.; Zhang, W., B. J. Am. Chem. Soc.
, 125, 99
3. Zhou, X., H J., C.; Pei, J . Lett. 2003, 5, 3543.
4.
awakam zawa, A.; T A. J. Org. C 2005, 70, 3939-3949.
, V. J.; Dhar, D.; Lindeman, S. V.; Rathore, R. Organic Letters 2006, 8,
ger, R. J. Org. Chem.
2000, 65, 6202.
10. Jiang, N.; Wang, J. Tetrahedron Lett. 2002, 43, 1285.
3747.
2
2003 44.
.; Yan, . Org
Ito, S.; Ando, M.; Nomura, A.; Morita, N.; Kabuto, C.; Mukai, H.; Ohta, K.;
K i, J.; Yoshi ajiri, hem.
5. Rausch, D.; Lambert, C. Organic Letters 2006, 8, 5037-5040.
6. Chebny
5041-5044.
7. Mio, M. J.; Kopel, L., C.; Braun, J. B.; Gadzikwa, T. L.; Hull, K. L.; Brisbois, R.
G.; Markworth, C. J.; Grieco, P. A. Org. Lett. 2002, 4, 3199.
8. Bordwell, F. G. Acc. Chem. Res. 1998, 21, 456.
9. Kalijurand, I.; Rodima, T.; Leito, I.; Koppel, I. A.; Schwesin
11. G. Inorg. Chim. Acta. 1995, 228, 147.
153
Chapter Six
Experimental Section
6.1 Monomers and Polymers Synthesized in Chapter Two
1,4-Dibromo-2,5-bis(bromomethyl) benzene 2.1
2.6g 1,4-Dibromo-2,5-dimethylbenzene (2.6g, 10 mmol), NBS (3.9g, 22mmol) and a
catalytic amount of benzoyl peroxide were mixed in carbon tetrachloride (100 ml). The
suspension was refluxed under irradiation for 4h. After the reaction mixture was cooled
to room temperature, 300 ml methylene chloride was added in and did the filtration to
remove the inorganic salts. The filtrate was washed with water (150ml x 3) and brine
drous magnesium sulfate. After
ltration, the solvent was removed by rotary evaporation to give white solid. The crude
%) white crystal
solid. 1H NMR (CDCl3, 300 MHZ, ppm) δ 7.64 (s, 2H), 4.49 DCl3,
75.5MHZ, ppm δ 1 8.96, 13 3 , 123.26 1 5. MS ): 4 .
1,4-Dibromo-2,5-bis(methoxymethyl)benzene 3.2
Sodium (1.16 g, 50 mmol) was added slowly to methanol (100 ml) under nitrogen with
cooling bath was
moved. 1,4-Dibromo-2,5-bis(bromomethyl)benzene (4.22 g, 10 mmol) in THF was
ly and the mixture was refluxed for 12 h. When the reaction was
through a short silica gel column using hexane and methylene chloride (5:1) as eluant to
(150ml). The organic mixture was dried over anhy
fi
product was recrystallized twice from ethanol to give 2.7g (Yield: 65
(s, 4H). 13C NMR (C
): 3 5. 3 , 3 .4 (EI, m/z 21.0 (M+)
water-bath cooling. When the vigorous reaction moderated, the
re
then added slow
completed, water was added in. The mixture was extracted three times with ether and
washed sequentially with water and brine. The organic layer was dried over anhydrous
magnesium sulfate and evaporated to give a yellow residue. The residue was passed
154
give 3.04 g (Yield: 94%) white solids. Mp: 75-77 C. 1H NMR (CDCl3, 300MHz, ppm):
7.63 (s, 2H), 4.47 (s, 4H), 3.47 (s, 6H). 13C NMR (CDCl3, 75.5 MHz, ppm): 138.3,
132.2, 121.1, 73.1, 58.7. MS (EI, m/z): 324.
2-bromo-9, 9-di-n-hexylfluorene 5. 3
A solution of 1-bromohexane (12.7g, 77mm ) in DMSO (15ml) was added to a mixture
of 2-bromofluorene (7.6g, 31 mmol), a catalyst amount of tetrabutylammonium bromide
and 50 % (w/w) aqueous NaOH (12ml) in DMSO (60 ml). The reaction mixture was
cooled to room temperature and stirred for 12 hours. 300 ml Dichloromethane was added
in. The mixture was extracted by water (150ml x 5) to remove the DMSO and salt. Rotar
evaporator was used to remove the organic solvent. Pure hexane was used to run the
silica gel column to obtain the colorless oil product. Yield: 10.3 g (90%). 1H NMR
(CDCl3, 300 MHZ, ppm) δ 7.69-7.33 (m, 7H), 1.99-1.85(m, 4H), 1.33-0.60(m, 22H). 13C
NMR(CDCl3, 75.5MHZ, ppm) δ 152.98, 150.31, 140.14, 140.03, 130.15, 127.43, 126.90,
126.14, 122.86, 121.09, 120.98, 119.72, 55.36, 40.28, 31.45, 29.63, 23.67, 22.54, 13.94.
MS (EI, m/z): 412.1(M+).
9, 9-di-n-hexylfluorene-2-bronic acid 6.4
A solution of BuLi (9.8ml, 15.7mmol, 1.6M in hexane) in THF was added slowly into
a stirring mixture of 2-bromo-9,9-di-n-hexyl luorene (5.0g, 12.1mmol) and 50 ml THF
under nitrogen at -78 oC. After keeping at this temperature for 2 hours, trimethyl borate
(2.8g, 24mmol) was added. The reaction mixture was stirred for 24 hours to room
temperature. The mixture was poured into crushed ice containing sulfuric acid (5%)
ol
f
155
while stirring. The mixture was extrac yl acetate and the combined extracts
hexane – acetone (1:2) afforded 2.2g (50%) white solid. This solid was used directly to
, 9
propan anic
ure was dried over
evaporation to give colorless oil. The crude product was purified by column
oma
(Yield: ), 7.36-7.31(m, 3H),
2(t, (m, 22H). 13C NMR (CDCl3,
122.83, 119.92, 118.81, 61.96, 54.90, 40.37, 31.49, 29.72, 27.42, 23.69, 22.57, 13.97. MS
m/
,4-bis (9, 9-di-n-hexylfluorenyl)-2,5-bis(methoxymethyl) benzene 8.
To a 100 ml one neck flask was added 9,9-di-n-hexylfluorene-2- trimethylene boronate
.73g, 16 mmol), 1, 4 – Dibromo – 2,5- bis(bromomethyl) benzene(2.17 g, 6.7 mmol),
atalytic amount of Bu4NBr and 40 ml toluene. Once all the monomers were dissolved,
7 ml 2 M Na2CO3 aqueous solution was added. The flask equipped with a condenser
ted with eth
were evaporated to give a yellow solid. Recrystallization of the crude product from
next step without characterization.
9, 9-di-n-hexylfluorene-2- trimethylene boronate 7.5
9 -di-n-hexylfluorene-2-bronic acid (2.0g, 5.3mmol) was refluxed with 1, 3-
diol (1.0 g, 16.5 mmol) in 50 ml toluene for 12h. After working up, the org
layer was washed with water (50ml x 2) and brine. The organic mixt
anhydrous magnesium sulfate. After filtration, the solvent was removed by rotary
chr tography eluting with 50% dichloromethane in hexanes to yield 1.9g colorless oil
88%). 1H NMR (CDCl3, 300 MHZ, ppm) δ 7.82-7.7(m, 4H
4.2 J=5.6HZ, 4H), 2.11-1.94(m, 6H), 1.16-0.61
75.5MHZ, ppm) δ 151.23, 149.66, 143.49, 141.08, 132.40, 127.78, 127.21, 126.57,
(EI, z): 418.4(M+).
1
(6
c
2
156
was then evacuated and filled wit imes to remove traces of air. Pd
(PPh3)4 (155 mg, 2% mmol) was then added un osphere. The flask
was again evacuated and filled with nitrogen three times. The reaction mixture was then
ixture was then
l water. The resulting mixture was
3
3.61 mmol) in 100 ml CHCl3
2 3
3
h nitrogen three t
der the nitrogen atm
heated to 95 – 100 oC and maintained for 48 h under nitrogen. The m
cooled to room temperature and poured into 100m
extracted with ether (80ml x 3) and the combined organic extracts were washed with
water and brine. The organic mixture was dried over anhydrous magnesium sulfate.
After filtration, the solvent was removed by rotary evaporation to give a colorless liquid.
The product was purified by column chromatography (eluent: n-hexane/ ethyl acetate = 6:
1) to offer 3.9 g (yield: 70%) white solid. 1H NMR (CDCl , 300 MHZ, ppm) δ 7.78-
7.73(m, 4H), 7.59(s, 2H), 7.45-7.23(m, 10H), 4.43(m, 4H), 3.38(m, 6H), 2.03-1.98(m,
8H), 1.14-1.07(m, 24H), 0.79-0.65(m, 20H). MS (EI, m/z): 831.0 (M+).
1,4-bis (9, 9-di-n-hexylfluorenyl)-2,5-bis(bromomethyl) benzene 9.
HBr gas was bubbled vigorously through a solution of 1, 4-bis (9, 9-di-n-
hexylfluorenyl)-2, 5-bis (methoxymethyl) benzene (3.0g,
for 20 minutes. The reaction mixture was stirred for an additional 20h in room
temperature and neutralized with 2 M Na CO aqueous solution. The organic layer was
washed with water (100ml x 3) and brine. Then it was dried over anhydrous magnesium
sulfate. After filtration, the solvent was removed by rotary evaporation to give a pale
yellow solid (3.18g, Yield, 95%) without further purification. . 1H NMR (CDCl , 300
MHZ, ppm) δ 7.88-7.74(m, 4H), 7.57-7.54(m, 4H), 7.43-7.26(m, 8H), 4.50(s, 4H), 2.05-
2.00(m, 8H), 1.16-1.11(m, 24H), 0.79-0.67(m, 20H). MS (ESI, m/z): 928.2(M+).
157
Poly[2,5-di(9,9-dihexylfluorene-2-yl)-1,4-phenylenevinylene] 10.
A solution of 1, 4-bis (9, 9-di-n-hexylfluorenyl)-2, 5-bis (bromomethyl) benzene (9)
67mg, 0.4mmol) in 15 ml anhydrous THF was added to a solution of 1M potassium
rred in room temperature under the protection of
nd brine (150ml) to remove most of the DMF. The organic
ixture was dried over anhydrous magnesium sulfate. After filtration, the solvent was
ight brown solid. Do the recrystallization in
(3
tert-butoxide (3ml). The mixture was sti
nitrogen for 24 hours. After that, the mixture was poured into 250ml of methanol with
stirring. The resulting green yellow precipitate was collected by filtration and redissolved
in chloroform and reprecipitated in methanol for two times. The solid was extracted
through Soxhlet extractor with methanol for 24 hours and finally dried under vacuum to
afford 167 mg (Yield: 55%) yellow green polymer.
3-Bromo carbazole 12.6
Carbazole (3.60 g, 1.6 mmol) was dissolved in 60 ml DMF in a 100ml flask. NBS
(3.84g, 21.6 mmol) was added in. The reaction mixture was heated to 80 oC and stirred
for 12h. 150 ml chloroform was added in to the flask. The resulting mixture was washed
with water (150ml x 4) a
m
removed by rotary evaporation to give a l
methanol to obtain 3.82 g (Yield: 72%) white product. 1H NMR (300 MHz, DMSO-d6) δ
11.42 (s, 1H), 8.33 (s, 1H), 8.12 (d, 1H, J = 7.7 Hz), 7.52-7.41 (m, 4H), 7.14 (t, 1H, J =
7.3 Hz,). 13C NMR (DMSO-d6, 75.5MHZ, ppm) δ 140.1, 138.0, 127.7, 126.5, 124.2,
122.9, 121.3, 120.5, 118.8, 112.8, 111.5, 110.3. MS (EI, m/z): 245.0(M+).
158
3-Bromo-N-hexyl-carbazole 13.6
3-bromo- carbazole (1.93g, 7.84 mmol) was dissolved in 50 ml DMSO. KOH (0.48g,
8.62 mmol) was added into the solution. After stirring 30 minutes, n- bromohexane was
added (1.43 ml, 10mmol). The resulting mixture was heated to 50 oC and stirred for 10h.
50 ml chloroform was added into the mixture. The resulting mixture was washed with
f the DMF. The organic mixture
e 1.6 M n-BuLi in hexane (6.5 ml, 10.40 mmol) under nitrogen.
he resulting mixture was stirred for 1h while maintaining the temperature at -78 oC,
l, 20.8 mmol)
1
water (100ml x 4) and brine (150ml) to remove most o
was dried over anhydrous magnesium sulfate. After filtration, the solvent was removed
by rotary evaporation to give a brown solid. Do the recrystallization in methanol to obtain
2.33g (Yield: 90%) white product. 1H NMR (CDCl3, 500 MHZ, ppm) δ 8.24 (s, 1H),
8.08-8.07 (d, 1H, J = 7.6 HZ), 7.58-7.51 (m, 2H), 7.44-7.42 (m, 1H), 7.31-7.26 (m, 2H),
4.29-4.26 (t, 2H, J = 7.25 HZ), 1.90-1.85 (m, 2H), 1.41-1.30 (m, 6H), 0.92-0.90 (t, 3H, J
= 6.63 HZ). 13C NMR (CDCl3, 125MHZ, ppm) δ 140.74, 139.09, 128.22, 126.34, 124.59,
123.08, 121.84, 120.54, 119.20, 111.52, 110.12, 108.94, 43.22, 31.57, 28.89, 26.95, 22.55,
14.01. MS (EI, m/z): 329.1(M+).
N-hexyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxoborolanyl)-carbazole 14.7
To a solution of 3-bromo-N-hexyl-carbazole (2.45g, 7.42 mmol) in THF (50 ml) at -78
oC was added dropwis
T
after which 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (4.2m
was added and the mixture was stirred at -78 oC for an additional hour. The reaction
mixture was then allowed to warm to room temperature and stirred for 24h. The mixture
was then cooled to 0 oC and 2N HCl (40ml) was added in. After the mixture was stirred
for 10 minutes, it was extracted with diethyl ether (100ml x 2). The organic layer was
159
washed with water and dried over anhydrous magnesium sulfate. After filtration, the
solvent was removed by rotary evaporation to give a brown viscous liquid. The crude
product was purified by column chromatography (eluent: n-hexane/ ethyl acetate = 30: 1)
to obtain a yellow liquid. (2.07g, Yield: 74%) 1H NMR (CDCl3, 500 MHZ, ppm) δ 8.70(s,
1H), 8.23-8.21(d, 1H, J= 10HZ), 8.02-8.00(d, 1H, J=10 HZ), 7.54-7.51(m, 1H), 7.51-
7.45(m, 2H), 7.33-7.28(m, 1H), 4.35-4.32(t, 2H, J=7.5 HZ) 1.94-1.88(m, 2H),
1.48(s,12H), 1.44-1.32(m, 6H), 0.95-0.92(t, 3H, J=7.5 HZ). 13C NMR(CDCl3, 125MHZ,
ppm) δ 142.55, 140.47, 132.05, 127.71, 125.53, 123.06, 122.55, 120.48, 119.13, 108.66,
108.02, 83.48, 43.00, 31.50, 28.83, 26.86, 24.88, 22.45, 13.94.
1,4-bis (N-hexylcarbazole-3-yl)-2, 5-bis(methoxymethyl) benzene 15.
To a 100 ml one neck flask was added N-hexyl-3-(4,4,5,5-tetramethyl-1,3,2-
ioxoborolanyl)-carbazole (1.40g, 3.7 mmol), 1,4-Dibromo-2,5- bis(bromomethyl)
luene. Once all the
ation to
d
benzene (0.50 g, 1.5 mmol), catalytic amount of Bu4NBr and 40 ml to
monomers were dissolved, 27 ml 2 M Na2CO3 aqueous solution was added. The flask
equipped with a condenser was then evacuated and filled with nitrogen three times to
remove traces of air. Pd (PPh3)4 (36 mg, 2% mmol) was then added under a nitrogen
atmosphere. The flask was again evacuated and filled with nitrogen three times. The
reaction mixture was then heated to 95 – 100 oC and maintained for 72 h under nitrogen.
The mixture was then cooled to room temperature and poured into 100ml water. The
resulting mixture was extracted with ether (80ml x 3) and the combined organic extracts
were washed with water and brine. The organic mixture was dried over anhydrous
magnesium sulfate. After filtration, the solvent was removed by rotary evapor
160
give a brown liquid. The product was purified by column chromatography (eluent: n-
NMR (CDCl3, 500
yl) benzene 16.
HBr gas was bubbled vigorously through a solution of 2.50g (3.76 mmol) 1, 4-bis (N-
bis (bromomethyl) benzene in 100 ml CHCl3 for 20 minutes.
.07.
hexane/ ethyl acetate = 30: 1) to offer 0.73 g solid (yield: 71%). 1H
MHZ, ppm) δ 8.31-8.30 (d, 2H, J= 1.85 HZ), 8.21-8.19 (d, 2H, J = 8.20 HZ), 7.37 (s, 2H),
7.68-7.66 (m, 2H), 7.57-7.49 (m, 6H), 7.33-7.30 (t, 2H, J = 7.25 HZ), 4.56 (s, 4H), 4.42-
4.39 (t, 4H, J = 7.25 HZ), 2.00-1.94 (m, 4H), 1.52-1.39 (m, 12H), 0.97-0.95 (t, 6H, J =
7.25 HZ). 13C NMR(CDCl3, 75.5MHZ, ppm) δ 141.47, 140.90, 139.76, 135.01, 131.60,
131.29, 127.30, 125.79, 123.00, 122.77, 121.22, 120.43, 118.93, 108.85, 108.23, 72.79,
58.27, 43.30, 31.67, 29.09, 27.10, 22.65, 14.10.
1,4-bis (N-hexylcarbazole-3-yl)-2,5-bis(bromometh
hexylcarbazole-3-yl)-2, 5-
The reaction mixture was stirred for an additional 20h and neutralized with 2 M Na2CO3
aqueous solution. The organic layer was washed with water (100ml x 3) and brine. Then
it was dried over anhydrous magnesium sulfate. After filtration, the solvent was removed
by rotary evaporation to give a pale blue solid (2.54g, Yield, 89%) without further
purification. 1H NMR (CDCl3, 500 MHZ, ppm) δ 8.31-8.30 (d, 2H, J = 1.25 HZ), 8.19-
8.18 (d, 2H, J = 7.6 HZ), 7.69-7.67 (m, 2H), 7.65 (s, 2H), 7.56-7.48 (m, 6H), 7.31-7.29 (t,
2H, J = 6.93 HZ), 4.62 (s, 4H), 4.41-4.38 (t, 4H, J = 7.25 HZ), 1.99-1.94 (m, 4H), 1.51-
1.34 (m, 12H), 0.94-0.91 (t, 6H, J = 7.25 HZ). 13C NMR(CDCl3, 125MHZ, ppm) δ
142.17, 140.92, 139.91, 135.79, 133.63, 130.02, 126.72, 125.97, 122.90, 122.76, 120.90,
120.57, 119.04, 108.88, 108.54, 43.32, 32.38, 31.64, 29.04, 27.06, 22.60, 14
161
Poly[2,5-di(N-hexylcarbazol-3-yl)-1,4-phenylenevinylene] 17.
90 ml) under stirring at room temperature. The reaction
Cl solution. The
A solution of 1, 4-bis (N-hexylcarbazole-3-yl)-2, 5-bis (bromomethyl) benzene (16)
(326mg, 0.43mmol) in 13 ml anhydrous THF was added to a solution of 1M potassium
tert-butoxide (3ml). The mixture was stirred in room temperature under the protection of
nitrogen for 24 hours. After that, the mixture was poured into 250ml of methanol with
stirring. The resulting green yellow precipitate was collected by filtration and redissolved
in chloroform and reprecipitated in methanol for two times. The solid was extracted
through Soxhlet extractor with methanol for 24 hours and finally dried under vacuum to
afford 127 mg (Yield: 51%) yellow green polymer.
6.2 Monomers and Polymers Synthesized in Chapter Three
2,7-Dibromofluoren-9-one 2.8
CrO3 (4.8g, 48 mmol) was added to a suspension of 2,7-dibromofluorene ( 6.38 g,
19.72 mmol) in acetic anhydride (
mixture was stirred for 5 h. The mixture was poured into 1000ml 2% H
suspension was filtered off and washed with cold water. The product was recrystallized in
methanol to provide 6.0 g (90%) of the title product as a yellow solid. Mp 202-204 °C;
mp(lit.) 203-205 °C. 1H NMR (CDCl3, 500 MHZ, ppm) δ 7.80-7.79 (d, 2H, J= 1.9Hz);
7.66-7.65 (q, 2H, J= 1.25HZ and 1.9 HZ); 7.42-7.41 (d, 2H, J= 7.55 HZ). 13C
NMR(CDCl3, 125MHZ, ppm) δ 190.92, 142.28, 137.47, 135.31, 127.87, 123.33, 121.83.
MS (EI, m/z): 337.8(M+).
9-(9H-fluoren-9-ylidene)-2,7-dibromo-9H-fluorene 4.9
162
Fluorene (735mg, 4.42mmol) was dissolved in 30 ml of THF under argon and cooled
to -78 oC. n-Butyllithium (1.6M in hexane, 3.6ml, 5.75mmol) was added. After the
solution was stirred for 10 minutes, trimethylsilyl chloride (0.56ml, 4.42mmol) was
added, and the solution was stirred for an additional 10 minutes. A second portion n-
Butyllithium (1.6M in hexane, 3.0ml, 4.86mmol) was added, and the solution was stirred
for 7 minutes. 2, 7-Dibromofluoren-9-one (2) (1.49g, 4.42mmol) in 30ml of THF was
added, and the solution was allowed to warm to room temperature and to stir overnight.
After the reaction was completed, 75ml water and saturated NH4Cl were added, and the
resulting mixture was extracted with ether (100ml x 3) and the combined organic extracts
ere washed with water (100ml x 2) and brine. The organic mixture was dried over
oved by rotary
w
anhydrous magnesium sulfate. After filtration, the solvent was rem
evaporation to give an orange red solid. Recrystallization was made in hexane to obtain
1.50g (Yield: 70%) orange red product. 1H NMR (CDCl3, 500 MHZ, ppm) δ 8.51-8.50(d,
2H, J=1.9 HZ), 8.30-8.28(d, 2H, J=8.2 HZ), 7.71-7.69(d, 2H, J=7.6 HZ), 7.56-7.54(d, 2H,
J=8.2 HZ), 7.48-7.46(dd, 2H, J=1.9 and 1.9 HZ), 7.40-7.37(m, 2H), 7.28-7.25(m, 2H).
13C NMR (CDCl3, 125MHZ, ppm) δ 143.72, 141.84, 139.65, 138.82, 138.00, 137.67,
131.75, 130.18, 120.10, 127.33, 126.77, 121.07, 120.87, 120.18. MS (EI, m/z):
486.2(M+).
2,7-dibromo-9,9-di-n-hexylfluorene 5.10
A solution of 1-bromohexane (12.7g, 77mmol) in DMSO (15ml) was added to a
mixture of 2, 7-dibromofluorene (10.0g, 31 mmol), a catalyst amount of
tetrabutylammonium bromide and 50 % (w/w) aqueous NaOH (12ml) in DMSO(60 ml).
163
The reaction mixture was cooled to room temperature and stirred for 12 hours, 300 ml
dichloromethane was added, the mixture was extracted by water (150ml x 5) to remove
most of the DMSO and salt, rotary evaporator was used to remove the organic solvent,
pure hexane was used to run the silica gel column to obtain the colorless solid product.
Yield: 14.2 g (93%). Mp: 65-66 oC. 1H NMR (CDCl3, 300 MHZ, ppm) δ 7.52-7.47(m,
4H), 7.44-7.43(m, 2H), 1.93-1.87(m, 4H), 1.16-1.03(m, 12H), 0.75(t, 6H, J=7.0 HZ),
0.60-0.58(m, 4H). 13C NMR(CDCl3, 125MHZ, ppm) δ 152.55, 139.00, 130.11, 126.20,
121.40, 121.09, 55.61, 40.12, 31.49, 29.56, 23.60, 22.50, 13.94. MS (EI, m/z): 492.0(M+).
ith 1,3-
ropandiol (2.0 g , 33.0 mmol) in 50 ml toluene for 12h. After working up, 50 ml water
9, 9-di-n-hexylfluorene-2,7-dibronic acid 6.5
A solution of BuLi (19.6ml, 31.4mmol, 1.6M in hexane) in THF was added slowly into
a stirring mixture of 6.0g (12.1mmol) 2, 7-dibromo-9, 9-di-n-hexylfluorene and 50 ml
THF under nitrogen at -78 oC. After keeping at this temperature for 2 hours, 5.6g
trimethyl borate (48mmol) was added. The reaction mixture was stirred for 24 hours to
room temperature. The mixture was poured into crushed ice containing sulfuric acid (5%)
while stirring. The mixture was extracted with ethyl acetate and the combined extracts
were evaporated to give a yellow solid. Recrystallization of the crude product from
hexane – acetone (1:2) afforded 3.0g (61%) white solid. This solid was used directly to
next step without purification and characterization.
9,9-di-n-hexylfluorene-2,7- bis(trimethylene boronate) 7.5
9,9-di-n-hexylfluorene-2,7-dibronic acid (2.2g, 5.3mmol) was refluxed w
p
164
was added and the resulting mixture was extracted with ether (50ml x 2) and the
, 27.43, 23.69, 22.62, 13.99. MS
I, m/z): 502.0(M+).
thyl-1,3,2–dioxoborolane-2-yl)-carbazole 11.
ith water and dried over anhydrous magnesium sulfate. After
ltration, the solvent was removed by rotary evaporation to give a brown viscous liquid.
aphy (eluent: n-hexane/ ethyl
combined organic extracts were washed with water and brine. The organic mixture was
dried over anhydrous magnesium sulfate. After filtration, the solvent was removed by
rotary evaporation to give some colorless oil. The crude product was purified by column
chromatography eluting with 50% dichloromethane in hexanes to yield 2.3g (Yield: 88%)
white solid. 1H NMR (CDCl3, 500 MHZ, ppm) δ 7.77-7.67(m, 6H), 4.22-4.19(t, 8H,
J=5.39HZ), 2.11-2.07(m, 4H), 2.01-1.96(m, 4H), 1.11-1.00(m, 12H), 0.76-0.71(t, 6H,
J=6.98HZ), 0.56-0.53(m, 4H). 13C NMR (CDCl3, 125MHZ, ppm) δ 150.28, 143.51,
132.30, 127.84, 119.14, 62.00, 54.86, 40.36, 31.54, 29.77
(E
N-hexyl-3,6-bis(4,4,5,5-tetrame
To a solution of 3, 6-Dibromo-N-hexyl-carbazole (1.16g, 2.84 mmol) in THF (50 ml)
at -78 oC was added dropwise n-BuLi (5.33mL, 8.52 mmol, 1.6 M in hexane) solution
under nitrogen. The resulting mixture was stirred for 1h while maintaining the
temperature at -78 oC, after which 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane
(2.9 mL, 14.2 mmol) was added and the mixture was stirred at -78 oC for an additional
hour. The reaction mixture was then allowed to warm to room temperature and stirred for
24h. The mixture was then cooled to 0 oC and 2N HCl (40ml) was added in. After the
mixture was stirred for 10 minutes, it was extracted with diethyl ether (100ml x 2). The
organic layer was washed w
fi
The crude product was purified by column chromatogr
165
acetate = 30: 1) to obtain a yellow liquid. (0.93g, Yield: 65%) 1H NMR (CDCl3, 300
MHZ, ppm) δ 8.56(s, 2H), 7.80-7.77(dd, 2H, J=1.2 HZ), 7.27-7.24(dd, 2H, J=0.6 HZ),
4.17-4.13(t, 2H, J=7.2 HZ), 1.80-1.70(m, 2H), 1.26(s, 24H), 1.20-1.11(m, 6H), 0.80-
0.65(m, 3H). (EI, m/z): 503.2(M+).
Poly[9-(9H-fluoren-9-ylidene)-2,7-fluorenyl]-co-alt-2,7-(9,9-dihexylfluorene) P1.
To a 50 ml one neck flask was added 9-(9H-fluoren-9-ylidene)-2,7-dibromo-9H-
fluorene(4) (124mg, 0.26 mmol), 9, 9-di-n-hexylfluorene-2, 7- bis(trimethylene
boronate)(7) (128mg, 0.26 mmol), catalytic amount of Bu4NBr and 20 ml toluene. Once
all the monomers were dissolved, 15 ml 2 M Na2CO3 aqueous solution was added. The
flask equipped with a condenser was then evacuated and filled with nitrogen three times
to remove traces of air. Pd (PPh3)4 (12 mg, 4% mmol) was then added under a nitrogen
atmosphere. The flask was again evacuated and filled with nitrogen three times. The
reaction mixture was then heated to 95 – 100 oC and maintained for 72 h under nitrogen.
The mixture was then cooled to room temperature and poured into 200ml of methanol
with stirring. The resulting brown yellow precipitate was collected by filtration and
redissolved in chloroform and reprecipitated in methanol for two times. The solid was
extracted through Soxhlet extractor with methanol for 24 hours and finally dried under
acuum to afford 78 mg (Yield: 45%) brown yellow polymer. v
Poly[9-(9H-fluoren-9-ylidene)-2,7-fluorenyl]-co-alt-3,6-(N-hexylcarbazole) P2.
To a 50 ml one neck flask was added 9-(9H-fluoren-9-ylidene)-2,7-dibromo-9H-
fluorene(4) (483mg, 0.99 mmol), N-hexyl-3,6-bis(4,4,5,5-tetramethyl-1,3,2–
166
dioxoborolane-2-yl)-carbazole (11) (500mg, 0.99 mmol), catalytic amount of Bu4NBr
and 30 ml toluene. Once all the monomers were dissolved, 22 ml 2 M Na2CO3 aqueous
solution was added. The flask equipped with a condenser was then evacuated and filled
with nitrogen three times to remove traces of air. Pd (PPh3)4 (12 mg, 4% mmol) was then
added under a nitrogen atmosphere. The flask was again evacuated and filled with
nitrogen three times. The reaction mixture was then heated to 95 – 100 oC and maintained
for 72 h under nitrogen. The mixture was then cooled to room temperature and poured
into 400ml of methanol with stirring. The resulting brown yellow precipitate was
collected by filtration and redissolved in chloroform and reprecipitated in methanol for
hlet extractor with methanol for 24 hours
3) and the combined organic extracts
ere washed with water and brine. The organic mixture was dried over anhydrous
d by rotary evaporation to
two times. The solid was extracted through Sox
and finally dried under vacuum to afford 348 mg(Yield: 61%) brown yellow solid.
6.3 Molecules Synthesized in Chapter Four
2, 5-bis (9, 9-di-n-hexylfluoren-2-yl)-1, 4-bis (mercaptomethyl)benzene 10.
A solution of 1,4-bis (9,9-di-n-hexylfluorenyl)-2,5- bis(bromomethyl)benzene (623mg,
0.67mmol) and thiourea (153mg, 2.00mol) in 40 ml ethanol and 20 ml hexane was
refluxed for 2 h. Then KOH (0.3g, 5.40mmol) in 2ml water was added for another 2h
refluxing. After the reaction mixture was cooled down, 50ml 2N HCl was added. The
resulting mixture was extracted with ether (70ml x
w
magnesium sulfate. After filtration, the solvent was remove
give a viscous brown solid. The product was purified by silica gel column
chromatography (eluent: n-hexane/ ethyl acetate = 4: 1) to afford a brown liquid (364mg,
167
Yield: 65%). 1H NMR (CDCl3, 500 MHZ, ppm) δ 7.83-7.78(dd, 4H, J=7.60 and 6.95
HZ), 3.80-3.78(d, 4H, J=7.55 HZ), 2.07-2.03(m, 8H), 1.80-1.76(t, 2H, J=7.25HZ), 1.19-
1.05(m, 24H), 0.82-0.71(m, 20H). 13C NMR(CDCl3, 125MHZ, ppm) δ 150.94, 141.45,
140.72, 140.50, 138.93, 137.72, 131.41, 127.77, 127.21, 126.85, 123.79, 122.92, 119.80,
119.64, 55.21, 40.48, 31.55, 29.74, 26.52, 23.88, 22.59, 14.01.
5, 8, 14, 17-tetra (9, 9-di-n-hexylfluoren-2-yl) dithia[3.3]paracyclophane 11.
A solution of 2, 5-bis(9,9-di-n-hexylfluoren-2-yl)-1,4-bis(mercaptomethyl)benzene(10)
(321mg, 0.384mmol) and 1,4-bis (9, 9-di-n-hexylfluorenyl)-2,5-bis(bromomethyl)
benzene(9)(356mg, 0.384mmol) in 80 ml degassed toluene was added dropwise with
irring to a solution of KOH(431mg, 7.68mmol) in 300 ml ethanol and 100 ml hexane.
at room
st
After the addition was completed, the reaction mixture was stirred for 48h
temperature under the protection of nitrogen. The organic solvent was removed under
reduced pressure and 100 ml chloroform was added to dissolve the residue. The resulting
mixture was washed with water (100ml x 2) and brine. The organic mixture was dried
over anhydrous magnesium sulfate. After filtration, the solvent was removed by rotary
evaporation to give a pale solid. The crud product was purified by column
chromatography (eluent: n-hexane/ ethyl acetate = 1: 300) to afford 320mg (Yield: 52%)
pale yellow liquid. 1H NMR (CDCl3, 300 MHZ, ppm) δ 7.73-7.65(m, 4H), 7.50-7.26(m,
28H), 4.30-4.25(d, 4H, J=15HZ), 3.90-3.85(d, 4H, J=15HZ), 1.97-1.94(m, 16H), 1.10-
0.95(m, 48H), 0.77-0.67(m, 40H). 13C NMR(CDCl3, 75.5MHZ, ppm) δ 150.88, 150.77,
140.84, 140.22, 140.00, 139.48, 133.55, 132.06, 128.20, 126.98, 126.73, 124.32, 122.85,
168
119.84, 119.68, 55.14, 40.61, 40.47, 33.52, 31.59, 31.49, 29.82, 29.78, 23.88, 22.69,
13.96. MALDI-TOF: 1602.431
4, 7, 12, 15-tetra (9, 9-di-n-hexylfluoren-2-yl) [2.2]paracyclophane 12.
5, 8, 14, 17 - tetra (9, 9-di-n-hexylfluoren-2-yl) dithia [3.3]paracyclophane(11) (200mg,
lask
, 5-bis (N-n-hexylcarbazole -3-yl)-1, 4-bis (mercaptomethyl)benzene 19.
e(16)
0.13mmol) was dissolved in 50ml trimethyl phosphate in 100ml conical flask. The f
was put into a UV reactor (Hg, 180 W) and was irradiated for 24 h in room temperature.
The trimethyl phosphate was removed in vacuum. The resulting mixture was added
100ml chloroform and washed with water and brine. The organic mixture was dried over
anhydrous magnesium sulfate. After filtration, the solvent was removed by rotary
evaporation to give a yellow brown solid. The crude product was purified by column
chromatography (eluent: n-hexane/ ethyl acetate = 300: 1) to obtain a colorless liquid(170
mg, Yield: 88%). 1H NMR (500 MHz, CDCl3) δ 7.85-7.70(m, 8H), 7.62(s, 4H), 7.45-
7.35(m, 16H), 7.08-7.07(d, 4H, J=3.8 HZ), 3.69-3.63(m, 4H), 2.94-2.88(m, 4H), 2.04-
2.01(m, 16H), 1.15-0.98(m, 48H), 0.79-0.70(m, 40H). 13C NMR(CDCl3, 75.5MHZ, ppm)
δ 150.95, 150.91, 140.90, 140.39, 139.93, 139.49, 137.12, 132.29, 127.50, 126.98, 126.78,
123.94, 122.87, 119.84, 119.77, 55.12, 40.62, 40.45, 33.71, 31.55, 29.76, 23.93, 23.84,
22.56, 22.50, 13.97, 13.95. MALDI-TOF: 1538.154.
2
A solution of 1,4-bis (N-hexylcarbazole-3-yl)-2,5-bis(bromomethyl) benzen
(993mg, 1.31mmol) and thiourea (220mg, 2.86mmol) in 40 ml ethanol and 20 ml hexane
was refluxed for 2 h. Then KOH (0.32g, 5.76 mmol) in 2ml water was added for another
169
2h refluxing. After the reaction mixture was cooled down, 50ml 2N HCl was added. The
resulting mixture was extracted with ether (70ml x 3) and the combined organic extracts
were washed with water and brine. The organic mixture was dried over anhydrous
magnesium sulfate. After filtration, the solvent was removed by rotary evaporation to
give a viscous brown solid. The product was purified by silica gel column
chromatography (eluent: n-hexane/ ethyl acetate = 4: 1) to afford a pale yellow solid
(638mg, Yield: 73%). 1H NMR (CDCl3, 500 MHZ, ppm) δ 8.25-8.24(d, 2H, J=1.25 HZ),
8.19-8.17(d, 2H, J= 7.55 HZ), 7.64-7.62 (m, 2H), 7.55-7.48 (m, 8H), 7.31-7.28 (t, 2H,
J=6.93 HZ), 4.41-4.38 (t, 4H, J = 7.58 HZ), 3.87-3.86 (d, 4H, J = 7.55 HZ), 2.00-1.94 (m,
4H), 1.84-1.81 (t, 2H, J = 7.55 HZ), 1.52-1.30 (m, 12H), 0.95-0.92 (t, 6H, J = 7.25 HZ).
13C NMR(CDCl3, 75.5MHZ, ppm) δ 141.36, 140.92, 139.76, 137.76, 131.95, 131.04,
26.92, 125.91, 122.93, 122.81, 120.98, 120.51, 118.97, 108.86, 108.48, 43.31, 31.64, 1
29.05, 27.06, 26.66, 22.59, 14.05.
5, 8, 14, 17-tetra (N-n-hexylcarbazole -3-yl) dithia[3.3]paracyclophane 20.
A solution of 1, 4-bis (N-n-hexylcarbazole-3-yl)-2,5-bis(bromomethyl) benzene(18)
(285mg, 0.37mmol) and 2,5-bis(N-n-hexylcarbazole-3-yl)-1,4-
bis(mercaptomethyl)benzene (19) (250mg, 0.37mmol) in 80 ml degassed toluene was
added dropwise with stirring to a solution of KOH (420mg, 7.5 mmol) in 300 ml ethanol
and 100 ml hexane. After the addition was completed, the reaction mixture was stirred for
48h at room temperature under the protection of nitrogen. The organic solvent was
removed under reduced pressure and 100 ml chloroform was added to dissolve the
residue. The resulting mixture was washed with water (100ml x 2) and brine. The organic
170
mixture was dried over anhydrous magnesium sulfate. After filtration, the solvent was
removed by rotary evaporation to give a pale yellow solid. The crude product was
purified by column chromatography (eluent: n-hexane/ ethyl acetate = 30:1) to afford
207mg (Yield: 44%) pale yellow solid. 1H NMR (CDCl3, 500 MHZ, ppm) δ 8.23 (s, 4H),
7.86-7.85 (d, 4H, J = 1.25 HZ), 7.60-7.34 (m, 20H), 6.79-6.76 (t, 4H, J = 7.25 HZ), 4.43-
.40 (d, 4H, J = 15.15 HZ), 4.39-4.36 (t, 8H, J = 7.25 HZ), 4.03-4.00 (d, 4H, J = 15.15
C NMR
4.38 (t, 8H, J = 7.55 HZ), 3.80-3.74 (m, 4H), 3.04-2.98 (m, 4H), 1.99-1.93 (m, 8H), 1.51-
4
HZ), 1.97-1.91 (m, 8H), 1.49-0.89 (m, 24H), 0.92-0.89 (t, 12H, J = 7.25 HZ). 13
(CDCl3, 125MHZ, ppm) δ 140.79, 140.20, 139.60, 133.54, 132.73, 132.00, 127.82,
125.59, 123.34, 123.01, 121.67, 120.56, 118.61, 108.48, 108.13, 43.33, 35.78, 31.61,
29.11, 27.10, 22.57, 14.04. MALDI-TOF: 1269.844
4, 7, 12, 15-tetra (N-n-hexylcarbazole -3-yl) [2.2]paracyclophane 21.
5, 8, 14, 17 - tetra (N-n-hexylcarbazole-3-yl)dithia[3.3] paracyclophane(20) (150mg,
0.12 mmol) was dissolved in 50ml trimethyl phosphate in 100ml conical flask. The flask
was put into a UV reactor (Hg, 180 W) and was irradiated for 24 h. The trimethyl
phosphate was removed in vacuum. The resulting mixture was added 100ml chloroform
and washed with water and brine. The organic mixture was dried over anhydrous
magnesium sulfate. After filtration, the solvent was removed by rotary evaporation to
give a pale yellow solid. The crude product was purified by column chromatography
(eluent: n-hexane/ ethyl acetate = 30: 1) to obtain a gray solid (121 mg, Yield: 85%). 1H
NMR (CDCl3, 500 MHZ, ppm) δ 8.11-8.10 (d, 4H, J = 1.25 HZ), 7.84-7.82 (m, 4H),
7.54-7.52 (d, 4H, J = 8.2 HZ), 7.44-7.34 (m, 12H), 7.22 (s, 4H), 6.80-6.77 (m, 4H), 4.41-
171
1.29 (m, 24H), 0.91-0.88 (t, 12H, J = 7.25 HZ). 13C NMR (CDCl3, 125MHZ, ppm) δ
140.72, 140.25, 139.49, 137.13, 132.76, 132.30, 127.38, 125.52, 123.43, 123.03, 121.10,
20.36, 118.56, 108.46, 108.38, 43.30, 33.63, 31.58, 29.69, 29.09, 27.05, 22.56, 13.99.
: 1) to afford 126 mg (Yield: 40%)
ale yellow solid. 1H NMR (CDCl3, 500 MHZ, ppm) δ 8.40 (s, 2H), 7.88-7.87 (d, 2H, J =
(d, 2H, J =
1
MALDI-TOF: 1205.522
5, 8-bis (N-n-hexylcarbazole-3-yl)-14, 17-bis (9, 9-n-hexylfluorene-2-yl) dithia[3.3]
paracyclophane 22.
A solution of 2,5-bis(9,9-di-n-hexylfluoren-2-yl) -1,4-bis(mercaptomethyl)benzene(10)
(186mg, 0.22mmol) and 1,4-bis (N-hexylcarbazole-3-yl)-2,5-bis(bromomethyl) benzene
(18) (169mg, 0.22mmol) in 80 ml degassed toluene was added dropwise with stirring to
a solution of KOH (250mg, 4.5 mmol) in 300 ml ethanol and 100 ml hexane. After the
addition was completed, the reaction mixture was stirred for 48h at room temperature
under the protection of nitrogen. The organic solvent was removed under reduced
pressure and 100 ml chloroform was added to dissolve the residue. The resulting mixture
was washed with water (100ml x 2) and brine. The organic mixture was dried over
anhydrous magnesium sulfate. After filtration, the solvent was removed by rotary
evaporation to give a yellow solid. The crude product was purified by column
chromatography (eluent: n-hexane/ ethyl acetate = 20
p
7.6 HZ), 7.76-7.71 (m, 6H), 7.53-7.09 (m, 22H), 4.46-4.37 (m, 8H), 4.13-4.10
15.75 HZ), 3.84-3.81 (d, 2H, J = 15.15 HZ), 2.02-1.99 (m, 4H), 1.58-0.69 (m, 70H). 13C
NMR(CDCl3, 125MHZ, ppm) δ 151.14, 151.06, 140.98, 140.90, 140.39, 140.00, 139.52,
133.68, 133.53, 132.55, 132.23, 131.56, 128.33, 128.03, 126.85, 126.63, 125.76, 123.87,
172
123.23, 122.98, 122.68, 121.77, 120.81, 119.65, 119.44, 118.91, 55.07, 43.33, 40.19,
39.92, 36.09, 35.33, 31.71, 31.68, 31.43, 29.74, 29.71, 29.54, 29.18, 27.13, 23.76, 23.72,
22.65, 22.62, 22.49, 14.08, 14.03. MALDI-TOF: 1436.520.
4, 7 - bis (N - n – hexylcarbazole - 3 - yl) - 12, 15-bis(9, 9 - n-hexylfluorene-2-yl) [2.2]
paracyclophane 23.
5, 8 –bis(9, 9’- di – n – hexyl– 9H- fluoren -2 – yl) – 1,4 – phenylene ) -2, 11- dithia [3,
3] paracyclophane (101mg, 0.07 mmol) was dissolved in 50ml trimethyl phosphate in
100ml conical flask. The flask was put into a UV reactor (Hg, 180 W) and was irradiated
for 24 h in room temperature. The trimethyl phosphate was removed in vacuum. The
resulting mixture was added 100ml chloroform and washed with water and brine. The
organic mixture was dried over anhydrous magnesium sulfate. After filtration, the
solvent was removed by rotary evaporation to give a yellow brown solid. The crude
duct was purified by column chromatography (eluent: n-hexane/ ethyl acetate = 20: 1)
) δ 8.17-
pro
to obtain a white solid (74 mg, Yield: 77%). 1H NMR (CDCl3, 500 MHZ, ppm
8.16 (d, 2H, J = 1.25 HZ), 7.85-7.81 (m, 4H), 7.76-7.67 (m, 4H), 7.54-7.49 (m, 6H),
7.43-7.28(m, 10H), 7.15 (s, 2H), 7.07 (s, 2H), 7.03-6.92 (m, 2H), 4.39-4.36 (t, 4H, J =
7.25 HZ), 3.80-3.70 (m, 4H), 3.03-2.94 (m, 4H), 2.00-1.93 (m, 4H), 1.73-0.56 (m, 70H).
13C NMR(CDCl3, 125MHZ, ppm) δ 151.15, 151.13, 140.98, 140.77, 140.44, 140.23,
140.04, 139.81, 139.45, 137.21, 136.95, 132.54, 132.48, 131.97, 128.65, 127.47, 126.88,
126.73, 125.59, 123.43, 123.34, 122.94, 122.79, 120.77, 120.59, 119.76, 119.65, 118.75,
108.57, 108.48, 55.04, 43.24, 40.37, 39.89, 33.69, 33.64, 31.93, 31.67, 31.56, 31.49,
173
31.21, 29.65, 29.64, 29.52, 29.36, 29.14, 27.07, 23.92, 23.78, 22.69, 22.62, 22.54, 22.33,
14.10, 14.04, 13.83. MALDI-TOF: 1373.907
1,4 –bis(thiophene-2-yl)-2,5-bis(methoxymethyl)benzene 26.
To a 150 ml one neck flask was added thiophen-2-ylboronic acid (2.77g, 21.6 mmol),
1,4-dibromo-2,5-bis(methoxymethyl)benzene (2.60g, 8.0 mmol), catalytic amount of
Bu4NBr and 60 ml toluene. Once all the monomers were dissolved, 40 ml 2 M Na2CO3
aqueous solution was added. The flask equipped with a condenser was then evacuated
and filled with nitrogen three times to remove traces of air. Pd (PPh3)4 (185 mg, 2%
mmol) was then added under a nitrogen atmosphere. The flask was again evacuated and
lled with nitrogen three times. The reaction mixture was then heated to 95 – 100 oC and
om temperature
fi
maintained for 72 h under nitrogen. The mixture was then cooled to ro
and poured into 100ml water. The resulting mixture was extracted with ether (80ml x 3)
and the combined organic extracts were washed with water and brine. The organic
mixture was dried over anhydrous magnesium sulfate. After filtration, the solvent was
removed by rotary evaporation to give a colorless liquid. The product was purified by
column chromatography (eluent: n-hexane/ ethyl acetate = 6: 1) to offer1.99 g (Yield:
76%) white solid. 1H NMR (CDCl3, 500 MHZ, ppm) δ 7.63 (s, 2H), 7.39-7.38 (m, 2H),
7.21-7.20 (m, 2H), 7.13-7.11 (m, 2H), 4.50 (s, 4H), 3.42 (s, 6H). 13C NMR(CDCl3,
125MHZ, ppm) δ 141.25, 135.26, 133.75, 131.91, 127.39, 127.26, 125.96, 72.40, 58.10.
MS (EI, m/z): 329.9(M+). HRMS-EI: 330.0751, Δ = -0.8.
1, 4-bis (thiophene-2-yl)-2, 5-bis(bromomethyl) benzene 27.
174
HBr gas was bubbled vigorously through a solution of 1, 4 –bis(thiophene-2-yl)-2,5-
bis(methoxymethyl)benzene(26) (1.50g, 4.58 mmol) in 100 ml CHCl3 for 20 minutes.
The reaction mixture was stirred for an additional 20h and neutralized with 2 M Na2CO3
aqueous solution. The organic layer was washed with water (100ml x 3) and brine. Then
was dried over anhydrous magnesium sulfate. After filtration, the solvent was removed
(CDCl3, 500 MHZ, ppm) δ 7.60 (s, 2H), 7.46-7.40 (m, 4H), 7.19-
it
by rotary evaporation to give a pale yellow solid (1.78g, Yield, 91%) without further
purification. 1H NMR
7.17 (m, 2H), 4.62 (m, 4H). 13C NMR(CDCl3, 125MHZ, ppm) δ 139.76, 136.15, 134.44,
134.05, 127.68, 127.35, 126.51, 31.34.
5, 8 - bis(thiophene - 2 - yl) - 14, 17 - bis (9, 9 – di - n – hexylfluorene - 2 - yl)
dithia[3.3]paracyclophane 28.
A solution of 2,5-bis(9,9-di-n-hexylfluorene-2-yl) -1,4-
bis(mercaptomethyl)benzene(10) (322mg, 0.38 mmol) and 1,4-bis(thiophene-2-yl)-2,5-
bis(bromomethyl) benzene(27) (165mg, 0.38 mmol) in 80 ml degassed toluene was
added dropwise with stirring to a solution of 430mg KOH (7.7 mmol) in 300 ml ethanol
and 100 ml hexane. After the addition was completed, the reaction mixture was stirred for
48h at room temperature under the protection of nitrogen. The organic solvent was
removed under reduced pressure and 100 ml chloroform was added to dissolve the
residue. The resulting mixture was washed with water (100ml x 2) and brine. The organic
mixture was dried over anhydrous magnesium sulfate. After filtration, the solvent was
removed by rotary evaporation to give a pale yellow solid. The crude product was
purified by column chromatography (eluent: n-hexane/ ethyl acetate = 30: 1) to afford
175
180 mg (Yield: 43%) pale yellow solid. 1H NMR (CDCl3, 300 MHZ, ppm) δ 7.75-6.99
(m, 24H), 4.40-4.25(m, 4H), 4.11-4.06(d, 2H, J=15HZ), 3.61-3.56(d, 2H, J=15HZ), 1.93-
1.86(m, 8H), 1.27-0.69(m, 44H). 13C NMR(CDCl3, 75MHZ, ppm), 151.08, 150.89,
42.03, 140.97, 140.57, 139.96, 139.84, 134.43, 133.00, 132.66, 131.73, 127.83, 127.72,
.77, 23.74, 22.63, 14.13, 14.05. MALDI-TOF: 1100.268.
1
126.92, 126.69, 126.35, 123.34, 122.75, 119.66, 119.45, 55.10, 40.33, 40.25, 36.13, 35.21,
31.75, 31.55, 29.86, 29
4, 7 - bis(thiophene - 2 - yl) - 12, 15 - bis(9, 9 - di - n-hexylfluorene-2-yl) [2.2]
paracyclophane 29.
5,8-bis(thiophene-2-yl)-14,17-bis (9, 9 – di - n – hexylfluorene - 2 - yl)
dithia[3.3]paracyclophane(28) (100mg, 0.09 mmol) was dissolved in 50ml trimethyl
phosphate in 100ml conical flask. The flask was put into a UV reactor (Hg, 180 W) and
was irradiated for 24 h in room temperature. The trimethyl phosphate was removed in
vacuum. The resulting mixture was added 100ml chloroform and washed with water and
brine. The organic mixture was dried over anhydrous magnesium sulfate. After filtration,
the solvent was removed by rotary evaporation to give a yellow brown solid. The crude
product was purified by column chromatography (eluent: n-hexane/ ethyl acetate = 20: 1)
to obtain a white solid (77 mg, Yield: 82%). 1H NMR (CDCl3, 500 MHZ, ppm) δ 7.75-
7.03 (m, 24H) 3.79-3.75(m, 2H), 3.57-3.52(m, 2H), 3.21-3.15(m, 2H), 2.66-2.60(m, 2H),
2.03-1.91(m, 8H), 1.29-0.60(m, 44H). 13C NMR(CDCl3, 125MHZ, ppm), δ 151.19,
150.95, 142.81, 141.25, 140.99, 139.94, 139.65, 136.96, 133.75, 132.51, 132.21, 128.50,
127.86, 126.96, 126.77, 125.71, 125.51, 123.41, 122.79, 119.65, 119.60, 55.18, 40.53,
176
40.14, 33.47, 33.44, 31.70, 31.47, 29.79, 29.70, 29.66, 23.86, 23.67, 22.56, 14.10, 14.00.
MALDI-TOF: 1038.574.
5, 8 - bis (N - n - hexylcarbazole - 3 - yl) – 14, 17 – bis (9, 9 - di - n-hexylfluorene - 2 -
20.77, 120.52, 118.58, 114.09,
8.66, 108.22, 43.21, 36.13, 35.75, 31.95, 31.62, 29.72, 29.38, 29.02, 27.04, 22.71,
yl) dithia[3.3]paracyclophane 30.
A solution of 2, 5-bis(N-n-hexylcarbazole-3-yl)-1,4-bis(mercaptomethyl)benzene(19)
(276mg, 0.41 mmol) and 1,4-bis(thiophene-2-yl)-2,5-bis(bromomethyl) benzene(27)
(177mg, 0.41 mmol) in 80 ml degassed toluene was added dropwise with stirring to a
solution of 460mg KOH (8.2 mmol) in 300 ml ethanol and 100 ml hexane. After the
addition was completed, the reaction mixture was stirred for 48h at room temperature
under the protection of nitrogen. The organic solvent was removed under reduced
pressure and 100 ml chloroform was added to dissolve the residue. The resulting was
washed with water (100ml x 2) and brine. The organic mixture was dried over anhydrous
magnesium sulfate. After filtration, the solvent was removed by rotary evaporation to
give a pale yellow solid. The crude product was purified by column chromatography
(eluent: n-hexane/ ethyl acetate = 20: 1) to afford 165 mg (Yield: 43%) pale yellow solid.
1H NMR (CDCl3, 500 MHZ, ppm) δ 7.97-7.24(m, 24H), 4.57-4.53(d, 2H, J=21 HZ),
4.36-4.31(m, 6H), 4.17-4.14(d, 2H, J=15.0HZ), 3.73-3.70(d, 2H, J= 15.0HZ), 1.97-
1.91(m, 4H), 1.58-1.30(m, 16H), 0.95-0.92(t, 6H, J=7.5HZ), 13C NMR(CDCl3, 125MHZ,
ppm), δ 142.52, 140.74, 140.30, 139.56, 134.43, 132.87, 132.74, 132.57, 132.07, 131.75,
127.84, 127.77, 127.37, 126.42, 125.60, 123.07, 123.01, 1
10
14.14. MS (EI, m/z): 604.6(M+). MALDI-TOF: 935.05
177
4, 7 - bis (N - n - hexylcarbazole - 3 - yl) - 12, 15 - bis (9, 9 - di – n -hexylfluorene - 2 -
yl) [2.2]paracyclophane 31.
5, 8 - bis (N - n - hexylcarbazole - 3 - yl) – 14, 17 – bis (9, 9 - di - n-hexylfluorene - 2 -
yl) dithia[3.3]paracyclophane(30) (130mg, 0.14 mmol) was dissolved in 50ml trimethyl
phosphate in 100ml conical flask. The flask was put into a UV reactor (Hg, 180 W) and
was irradiated for 24 h in room temperature. The trimethyl phosphate was removed in
vacuum. The resulting mixture was added 100ml chloroform and washed with water and
brine. The organic mixture was dried over anhydrous magnesium sulfate. After filtration,
the solvent was removed by rotary evaporation to give a yellow brown solid. The crude
roduct was purified by column chromatography (eluent: n-hexane/ ethyl acetate = 20: 1)
7.98-7.97 (d, 2H, J = 7.6 HZ), 7.63-7.61 (m, 2H), 7.57-
m, 1 -7.28 2H), .16-7
p
to obtain a pale yellow solid (97 mg, Yield: 80%). 1H NMR (CDCl3, 500 MHZ, ppm) δ
8.05-8.04 (d, 2H, J = 1.25 HZ),
7.40 ( 2H), 7.30 (m, 7 .15 (d, 4H, J = 3.15 HZ), 4.37-4.34 (t, 4H, J =
7.25 HZ), 3.90-3.86 (m, 2H), 3.56-3.52 (m, 2H), 3.26-3.19 (m, 2H), 2.68-2.61 (m, 2H),
1.98-1.92 (m, 4H), 1.49-1.29 (m, 12H), 0.94-0.91 (t, 6H, J = 7.30 HZ). 13C NMR (CDCl3,
125MHZ, ppm) δ 143.35, 141.07, 140.72, 139.59, 136.95, 136.80, 133.60, 132.57,
132.37, 131.96, 127.98, 127.96, 125.59, 125.48, 125.44, 123.22, 123.09, 120.60, 120.54,
118.69, 108.75, 108.47, 43.25, 33.55, 33.52, 31.61, 29.71, 29.04, 27.03, 22.59, 14.03.
MALDI-TOF: 870.949
6.4 Molecules Synthesized in Chapter Five
2-Bromo-9,9-dihexylfluorene 1a.3
178
To a stirring solution of 2-bromofluorene (12.26g, 50.0 mmol) in DMSO(150ml) under
nitrogen, powered potassium tert-butoxide(15.16g, 135.0 mmol) was added and the
solution was cooled to room temperature. After 15 minutes, 1-bromohexane (17.6ml,
125.1mmol) in DMSO (20 ml) was added dropwise in 30 minutes. Following that, the
reaction temperature was then allowed to warm to 40 oC and the reaction mixture was
stirred overnight. Distilled water (150ml) was poured into the reaction mixture to quench
e reaction. The resulting mixture was extracted with CH2Cl2 (100ml x 3) and the
he organic mixture was dried over anhydrous magnesium sulfate.
th
combined organic extracts were washed with water (100ml x 5, to remove most of the
DMSO) and brine. T
After filtration, the solvent was removed by rotary evaporation to give a colorless liquid.
The crude product was purified by column chromatography eluting with pure hexane to
obtain 1a as colorless oil (20.2g, Yield: 98%). 1H NMR (CDCl3, 300 MHZ, ppm) δ 7.42-
7.67(m, 4H), 7.31-7.33(m, 3H), 1.90-1.95(m, 4H), 1.03-1.15(m, 12H), 0.77(t, 6H), 0.58-
0.62(m, 4H). 13C NMR(CDCl3, 75.5MHZ, ppm) δ 151.0, 150.7, 141.2, 140.3, 129.9,
127.5, 126.9, 126.1, 122.9, 121.0, 119.7, 55.2, 40.3, 31.5, 29.7, 23.7, 22.6, 14.0. MS(EI,
m/z): 414.2(M+).
2-Bromo-9, 9-dipropylfluorene 1b.3
The procedure of 1a was followed to obtain 1b from 2-bromofluorene(0.98g,
4.00mmol) as pale yellow oil (1.20g, Yield: 91%). 1H NMR (CDCl3, 300 MHZ, ppm) δ
7.54-7.77(m, 4H), 7.39-7.44(m, 3H), 2.03-2.08(m, 4H), 0.77-0.80(m, 10H). 13C
NMR(CDCl3, 75.5MHZ, ppm) δ 153.0, 150.3, 140.2, 130.0, 127.5, 127.0, 126.2, 122.9,
121.1, 121.0, 119.8, 55.6, 42.7, 17.2, 14.5. MS (EI, m/z): 328.0(M+).
179
2-Bromo-9, 9-dimethylfluorene 1c.3
The procedure of 1a was followed to obtain 1c from 2-bromofluorene(4.10g, 16.5
mol) as pale yellow oil (4.30g, Yield: 95%). 1H NMR (CDCl3, 500 MHZ, ppm) δ 7.75-
.73, 153.28, 138.28, 138.19, 130.14, 127.73, 127.23,
m
7.73(m, 1H), 7.64-7.62(m, 2H), 7.53-7.47(m, 2H), 7.40-7.39(m, 2H), 1.54(s, 6H). 13C
NMR(CDCl3, 125MHZ, ppm) δ 155
126.21, 122.70, 121.44, 121.09, 120.12, 47.15, 27.06. MS (EI, m/z): 271.7(M+).
1, 2-bis (9, 9-dimethylfluorene-2-yl)ethyne 2c.
2-Bromo-9, 9-dimethylfluorene (3.16g, 11.56mmol), Pd(PPh3)2Cl2 (0.26g, 0.72mmol)
and CuI (0.29g, 1.2mmol) were added to a 150ml round bottom flask containing 60 ml
benzene. The mixture was degassed with dry argon before adding DBU (10.8ml, 72.1
mmol) by a syringe. Following that, distilled water (0.1 ml, 4.8mmol) and ice-chilled
trimethylsilylacetylene (0.81ml, 5.73mmol) were added into the flask. The reaction
mixture was blocked from light and refluxed at 80 oC for 18 hours. The reaction mixture
was partitioned in ethyl ether and distilled water (100ml each). The organic layer was
washed with 10% HCl (3 X 80ml), saturated aqueous NaCl (100ml), dried over MgSO4,
gravity-filtered and the solvent was removed in vacuum. The crude product was purified
by column chromatography(eluent: n-hexane/ ethyl acetate = 10: 1) to obtain 3c as white
solid (1.50g, Yield: 75%). 1H NMR (CDCl3, 500 MHZ, ppm) δ 7.75-7.70(m, 4H), 7.64(s,
2H), 7.57-7.54(m, 2H), 7.45-7.44(m, 2H), 7.37-7.34(m, 4H), 1.52(s, 12H). 13C
NMR(CDCl3, 125MHZ, ppm) δ 153.91, 153.62, 139.35, 138.56, 130.65, 127.65, 127.10,
125.90, 122.66, 121.82, 120.26, 119.95, 90.33, 46.86, 27.04. MS (EI, m/z): 410.0 (M+).
180
1, 2-bis (9, 9-dihexylfluorene-2-yl)ethyne 2a.
The procedure for 2c was followed to prepare 2a from 1a( 1.00g, 2.42mmol) as white
d the resulting mixture was washed with water (100ml x 2) and
rine. The organic mixture was dried over anhydrous magnesium sulfate. After filtration,
n to give an orange yellow solid 3c(70mg,
ppm) δ 7.46-7.45(m, 7H), 1.29-7.14(m, 28H), 7.10-
6.98(m, 7H), 6.96-6.86(m, 7H), 1.05-1.00(m, 42H). 13C NMR(CDCl3, 125MHZ, ppm) δ
solid (0.50g, 66%). 1H NMR (CDCl3, 300 MHZ, ppm) δ 7.54-7.69(m, 8H), 7.32-7.34(m,
6H), 1.98(t, 8H), 1.05-1.15(m, 24H), 0.77(t, 12H), 0.58-0.66(m, 8H). 13C NMR(CDCl3,
75.5MHZ, ppm) δ 150.9, 150.7, 141.3, 140.4, 130.5, 127.4, 126.8, 125.8, 122.8, 121.5,
119.9, 119.5, 90.4, 55.1, 40.4, 31.5, 29.7, 23.6, 22.5, 13.9. MS(EI, m/z): 691.1 (M+).
1, 2-bis (9, 9-dipropylfluorene-2-yl)ethyne 2b.
The procedure for 2c was followed to prepare 2b from 1b (1.15g, 3.49mmol) as white
solid (0.63g, 82%).%). 1H NMR (CDCl3, 300 MHZ, ppm) δ 7.81-7.69(m, 8H), 7.47-
7.42(m, 6H), 2.11-2.09(m, 8H), 0.80(bs, 20H). 13C NMR(CDCl3, 75.5MHZ, ppm) δ
151.0, 150.8, 141.4, 140.5, 130.6, 127.5, 126.1, 122.9, 121.7, 120.0, 119.7, 90.6, 55.3,
42.8, 17.2, 14.5. MS (EI, m/z): 522.2 (M+).
1,2,3,4,5,6-hexakis(9,9-dimethylfluorene-2-yl)benzene 3c.
1, 2-bis (9, 9’-dimethylfluorene-2-yl)ethyne(200 mg, 0.48mmol) was dissolved in
dioxane(20ml) and the mixture was degassed for 20 minutes. After that, Co2(CO)8(30mg,
0.08 mmol) was added and the reaction mixture was refluxed for 48 hours. 100 ml
chloroform was added an
b
the solvent was removed by rotary evaporatio
35%). 1H NMR (CDCl3, 500 MHZ,
181
153.56, 152.40, 152.36, 152.32, 141.05, 140.90, 140.10, 140.06, 139.13, 135.99, 130.71,
130.62, 130.59, 130.51, 130.40, 126.71, 126.61, 126.51, 122.26, 122.21, 119.76, 119.65,
119.53, 118.50, 118.32, 46.17, 26.90, 26.76. MS (FAB, m/z): 1231.5 (M+). MALDI-TOF:
1231.425.
182
Reference
. Yu, W. L.; Pei, J.; Cao, Y.; Huang, W.; Heeger, A. J. Chem. Commun. 1999, 1837.
.; Mastrorilli, P.; Gigli, G.; Suranna, G.
1. Kim, J. E.; Song, S. Y.; Shim, H. K. Synth. Met. 2001, 121, 1665.
2. Bedard, T. C.; Moore, J. S. J. Am. Chem. Soc. 1995, 117, 10662.
3. Lee, S. H.; Tsutsui, T. Thin Solid Films 2000, 363, 76.
4. Kanibolotsky, A. L.; Berridge, R.; Skabara, P. J.; Perepichka, I. F.; Bradley, D. D.
C.; Koeberg, M. J. Am. Chem. Soc. 2004, 126, 13695.
5
6. Grisorio, R.; Piliego, C.; Fini, P.; Cosma, P
P.; Nobile, C. F. J. Phys. Chem. C. 2008, 112, 7005.
7. Paliulis, O.; Ostrauskaite, J.; Gaidelis, V.; Jankauskas, V.; Strohriegl, P.
Macromolecular Chemistry and Physics 2003, 204, 1706.
8. Rodriguez, J. G.; Tejedor, J. L.; La Parra, T.; Diaz, C. Tetrahedron 2006, 62,
3355.
9. Mills, N. S.; Burns, E. E.; Hodges, J.; Gibbs, J.; Esparza, E.; Malandra, J. L.;
Koch, J. J. Org. Chem. 1998, 63, 3017.
10. Promarak, V.; Saengsuwan, S.; Jungsuttiwong, S.; Sudyoadsuk, T.; Keawin, T.
Tetrahedron Letters 2006, 48, 89.
183
I
APPENDIX I
clei
ch as 1H, 13C, 15N, 17O and 19F have an odd number of nucleons and nuclear spin (I) of
ions. When a radio frequency is applied
requencies of the absorption peaks vs. peak
tensities constitutes a NMR spectrum.
lues, chemical shift values,
CHARACTERIZATION TECHNIQUES
Nuclear Magnetic resonance Spectroscopy (NMR)
NMR spectroscopy utilizes the magnetic properties of nuclei. In the presence of an
applied magnetic field, nuclear magnets can have an orientation in 2I+1 ways. Nu
su
½, hence they can take up one of the two orientat
to the system, this distribution is changed if the radio frequency matches the frequency at
which the nuclear magnets naturally process in the magnetic field. The radiation is
absorbed, and some nuclei in the low energy states are promoted to the higher energy
states. The absorptions are characterized by chemical shifts, which reflect the local
environment of the nuclei. A plot of the peak f
in
In 1H NMR spectroscopy, inference from the integral va
coupling constants and multiplicities provide important information about the number
and environment of different protons in the molecule. Similarly, 13C NMR spectroscopy
provides information on the kind of carbon atoms in the molecule and their environment.
Thus, NMR spectroscopy is an extremely powerful tool for studying the structure
properties of the monomers and the polymers, as well as the indication of the purity of
the products.
1H and 13C NMR spectra were recorded on Bruker DPX 300 and Bruker AMX 500 FT-
NMR spectrophotometer. Samples were analyzed in Chloroform-d or other deuterated
organic solvents. The chemical shift values were expressed relative to tetramethylsilane
as an internal standard.
Mass spectrometry (MS)
ass spectrometry involves the sorting of charged gas molecules according to their
asses. The sample is first ionized, and then allowed to be fragment and decompose. The
ons produced are accelerated by an electric field out of the ion source into a
ass-analysis sector. Mass-analysis is usually achieved in a magnetic sector. The
agnetic sector disperses the ions in curved trajectories that depend on the mass-to-
harge ratio. The mass-analyzed beam of ions is finally detected. In the commonly used
lectron-impact (EI) mode of MS, a mass spectrum is normally a plot of abundance
gainst m/z.
Mass spectrometry is useful to confirm the structure of the monomer. The mass spectra
f our monomer samples were obtained using a Micromass 7034E mass spectrometer.
igh resolution mass spectroscopy (HRMS) spectra were obtained by using either E-
CAN or peak match method.
ltraviolet-Visible Absorption Spectroscopy (UV-Vis)
UV-Vis spectrometers measure the absorption of light in the visible and “near”
ltraviolet region, i.e. in the 250-800 nm range. Ultraviolet radiation is absorbed by a
hromophore rather than the molecules as a whole. When absorption occurs, electronic
ansition of molecules takes place. It is thus particularly suitable for the study of
M
m
charged i
m
m
c
e
a
o
H
S
U
u
c
tr
II
electronic structure of conjugated pol ch contain extended π – conjugated
he Hewlett-Packard
UV-Vis-NIR spectrometer.
Photol
ur
this exc at of the absorbed radiation.
that occ
luminescence spectrometer with a xenon lamp as the light source.
Cyclic
oxidation events. It can be used to study the electrochemical behavior of species diffusing
an electrode surface, interfacial phenomena at an electrode surface and bulk properties
f materials in or on electrodes. It measures the current resulting from the (potential)
nction to polymers with a fixed scan rate expressed in mV/s. CV of the polymers were
erformed on an EG&G Parc model 273A potentiosat/galvanostat system with a three-
lectrode cell in a solution of [CH3(CH2)3]4NPF6 in dry and degassed acetonitrile at a
an rate of 100mV/s at room temperature under the protection of nitrogen. A platinum
ymers, whi
chains and exhibit unusual color changes.
T UV-Vis spectra were acquired from dilute organic solution on a
8452A diode array spectrometer or a Perkin-Elmer Lamba 900
uminescence Spectroscopy (PL)
D ing the process of absorbing ultraviolet or visible electromagnetic radiation,
molecules are elevated to an excited electronic state. Some molecules will emit part of
ess energy as light of a wavelength different from th
This process is photoluminescence, which can be considered as a deexcitation process
urs after excitation by photons.
The PL spectra of our products were measured on a Perkin-Elmer LS 50B
Voltammetry (CV)
Cyclic voltammograms is a dynamic electrochemical method for measuring reduction-
to
o
fu
p
e
sc
III
electrode (~0.08 cm2) was coated with a thin polymer film and was used as the working
electrode. A platinum wire was used as 3 electrode
was used as the
column is shorter for the larger molecules than
ifferential refractometer HPLC system using polystyrene as a standard and
the counter electrode and an Ag/AgNO
reference electrode.
Gel-Permeation Chromatography (GPC)
GPC, also known as size exclusion chromatography (SEC), is a chromatographic
method used to determine the average molecular weight distribution of a polymer
sample.1 In GPC, a packed column of inert support (a solid or gel) with a distribution of
microscopic pores is used to separate a sample into a distribution of sized molecules. The
separation is accomplished by diffusion of dissolved polymers in and out of the pores of
the packing as solvent is continuously passed through the column. The larger polymer
chains do not readily diffuse into the pores and may even be completely excluded. They
are retained less than smaller molecules, which can move freely into the pores of the
packing. The effective time spent in the
the intermediate or small sized polymer molecules. Thus the larger molecules are eluted
first followed by smaller molecules. As the name implies, SEC separates the polymer
according to size or hydrodynamic radius. This hydrodynamic radius is converted to a
molecular weight or equivalent molecular weight compared to that of a calibration
polymer (polystyrene) by means of a calibration curve.2
GPC measurement was conducted on a Waters 2690 Separation Module equipped with
a Waters 410 d
HPLC grade THF or Chloroform as eluents. The data obtained from a GPC analysis are
the weight average molecular weight (Mw), the number average molecular weight (Mn)
IV
and the polydispersity index (PI), which is the ratio of the weight- to number- average
molecular weight of a polymer.
sis (TGA)
against temperature and is particularly useful for defining the temperatures
d nitrogen flow rate of 70 cm3/min. An important piece of
ata obtained from TGA is the onset of decomposition of the polymer which relates to
requires two cells equipped with thermocouples in addition to a programmable furnace, a
Thermogravimetric Analy
TGA is an example of a thermal analysis method where the mass loss of a polymer is
recorded against linearly increasing temperature.1 The basic instrumental requirements
are simple: a precision balance, a programmable furnace and a recorder. The analysis can
be carried out in static or flowing atmosphere of an inert or active gas. TGA is widely
used in the study of thermal degradation mechanisms. In addition, the residue remaining
at high temperature gives the percent ash content of the sample. On the other hand,
differential thermogravimetric analysis (DTG) monitors the rate of change of weight with
time plotted
of initial onset of decomposition and maximum rates of decomposition.3
Thermogravimetric analysis (TGA) were conducted on a Du Pont Thermal Analyst
2100 system with a TGA 2950 thermogravimetric analyzer under a heating rate of 20
oC/min from 20 oC to 850 oC an
d
the lifetime of a PLED device.
Differential Scanning Calorimetry (DSC)
DSC involves the measurement of the difference in energy input to a sample and a
reference material while both are subjected to a controlled temperature program. DSC
V
recorder and a gas controller. The measured energy differential corresponds to the heat
content (enthalpy) or the specific heat capacity of the sample. The technique is most often
DSC was run on a Du Pont DSC 2910 module in conjunction with the Du Pont
of 20 oC/min from 20 oC to 250 oC and a
used for characterizing the Tg (glass transition temperature), Tm (the heat of fusion on
heating) and Tc (The heat of fusion on cooling).
Thermal Analyst system. A heating rate
nitrogen flow of 70 cm3/min were employed. The presence or absence of glass transition
behavior, defined as the freezing-in (upon cooling) or the unfreezing (upon heating) of
micro-Brownian chain-segmented motion involving lengths of 20-50 atoms, was
observed in the series of polymers.4
VI
VII
tographic Techniques; Noyes publication, 1996.
. Kroschwitz, J. I. Characterization of Polymers; Wiley-Interscience, 1990 Vol. 1.
sis of Polymers; Applied Science Publishers
Reference
1. Cheremisinoff, N. P. Chroma
2
3. Hay, J. N. Thermal Methods of Analy
Ltd., 1982, Chapter 6.
4. Boyer, R. F. Transitions and Relaxations; Wiley-Interscience, 1977.