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Accepted Manuscript
Synthesis, growth and characterization of a new metal-organic NLO material:
Dibromo bis (L-proline) Cd (II)
K. Boopathi, P. Ramasamy
PII: S0022-2860(14)00981-8
DOI: http://dx.doi.org/10.1016/j.molstruc.2014.09.067
Reference: MOLSTR 20975
To appear in: Journal of Molecular Structure
Received Date: 13 August 2014
Revised Date: 22 September 2014
Accepted Date: 22 September 2014
Please cite this article as: K. Boopathi, P. Ramasamy, Synthesis, growth and characterization of a new metal-organic
NLO material: Dibromo bis (L-proline) Cd (II), Journal of Molecular Structure (2014), doi: http://dx.doi.org/
10.1016/j.molstruc.2014.09.067
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
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1
Synthesis, growth and characterization of a new metal-organic NLO material:
Dibromo bis (L-proline) Cd (II)
K. Boopathi, P. Ramasamy*
Centre for Crystal Growth, SSN College of Engineering, Kalavakkam-603110, India.
Abstract
Single crystals of metal-organic complex dibromo bis (L-proline) Cd (II) (DBPC)
were grown by low temperature solution growth method. The synthesized material was
purified by the process of repeated recrystallization. The grown crystal was confirmed by
Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (1H NMR and 13C NMR)
spectral studies and single crystal X-ray diffraction. Single crystal X-ray analysis shows that
DBPC crystallizes in orthorhombic crystal system with space group P212121. The
coordination geometry around the cadmium (II) center is distorted tetrahedral. The title
compound was characterized by UV-Vis-NIR study shows that the crystal is transparent in
the wavelength range 200-1100 nm and TG/DTA analysis. The magnetic property of DBPC
is investigated at room temperature. The microhardness test was carried out. The second
harmonic efficiency of powdered DBPC was determined by Kurtz and Perry method and it is
2.25 times that of KDP
Key words: Chemical synthesis, Crystal structure, Growth from solutions, Optical properties, Magnetic materials, Nonlinear optical material
*Corresponding author
Phone: +91-9283105760, +914427475166
Email: proframasamy@hotmail.com; ramasamyp@ssn.edu.in
2
1. Introduction
In the last several decades, Non-Linear Optical (NLO) materials have attracted much
attention due to their potential uses in many fields, such as optical modulation, optical
switching, optical logic, frequency shifting, colour displays and optical data storage for the
developing technologies in telecommunication and in efficient signal processing [1–5].
Among various second order NLO materials, metal-organic coordination compounds have
attracted much more attention due to their capability of combining the advantage of both
organic and inorganic materials, such as high NLO coefficients, stable physico-chemical
properties and better mechanical intension [6–8]. NLO material capable of frequency
conversion is generally composed of an electron donor (D), an acceptor (A) and a conjugate
π -system as a bridge providing the electronic communication between the donor and
acceptor [9]. And for the second order NLO materials, the bridged system units must be
packed in a non-centrosymmetric way. In metal-organic compounds, metal centers can act as
both donors and the bridging moiety in D–π–A system, and the metal–ligand bond is
expected to display large molecular hyperpolarisability because of the transfer of electron
density between the metal atom and the conjugated ligand system [10]. Furthermore, in the
case of metal-organic coordination complex, the group IIB divalent d10ions, Zn2+, Cd2+, and
Hg2+ complexes have attracted our interest for their unique characteristics of pale colour and
high thermal stability.
Amino acids have two or more types of coordination atoms and can act as various
bridging ligands [11–13]. Taking advantage of the properties of the amino acid ligands, an
amino acid complex was used as a ligand in order to synthesize a new heteronuclear complex.
One of the continuing challenges in materials chemistry concerns the elucidation of structure
property relationships [14, 15]. This is especially true with second-order nonlinear optical,
i.e., SHG, materials [16].
3
L- Proline is an abundant amino acid in collagen and is exceptional among the amino
acids because it is the only one in which the amine group is part of a pyrrolidine ring, thus
making it rigid and directional in biological systems [17]. L-Proline has been exploited for
the formation of salts with different organic and inorganic compounds [18]. Single crystal of
l-proline shows no centre of symmetry and its NLO coefficients have been examined by
Boomadevi and Dhanasekaran [19]. Kandasamy et al., [20] have grown L-PCCM and
reported that the second harmonic generation efficiency of their crystal was twice that of
KDP. As metal atoms or ions occur widely in association with proteins and show a variety of
functions, one can expect that synthesizing the amino acid complexes with metal salts and
characterizing them would yield useful and informative results [21, 22]. In the present
communication, we report on the synthesis, crystal growth, and spectral characterization of
metal organic NLO crystal dibromo bis (L-proline) Cd (II) from aqueous solution by slow
evaporation method for the first time.
2. Experimental section
2.1. Materials synthesis, crystal growth
The starting material of L-proline and CdBr2 was taken in 2:1 stoichiometric ratio to
synthesise dibromo bis (l-proline) Cd (II). The reaction scheme is shown in Fig.1. The
calculated amount of cadmium bromide was first dissolved in deionized water.
L-proline was then added to the solution slowly by stirring. The prepared solution was
allowed to dry at room temperature and the salt was obtained by slow evaporation technique.
The purity of the synthesized salt was improved by successfully recrystallization. After 25
days of growth, transparent single crystal of dimension 12mm×9mm×4 mm was obtained by
slow evaporation technique. The as grown crystals are shown in Fig.2. The crystal had good
compositional stability and showed no degradation when stored in the open air for several
months.
4
3. Results and discussion
3.1. Spectroscopic studies
The FT-IR spectrum of (DBPC) is recorded using a JASCO FT-IR 410 spectrometer
by the KBr pellet method. The vibrational spectroscopy provides evidence for the charge
transfer interaction between the donor and acceptor groups through π-electron movement.
The intra molecular hydrogen bonding network is formed between amino hydrogen’s of
dibromo bis (L-proline) Cd (II) atoms. The FT-IR spectrum (Fig. 3) shows the strong peak at
3028 cm-1 due to N+-H stretching frequency. The strong peak at 1633 cm-1 and 1552 cm-1 can
be assigned to the C=O stretching of asymmetric and symmetric vibrations of COO- groups.
The peak at 1331 cm-1 is assigned to the NH2+ wagging. The peaks observed between
2732 -3028 cm-1 are the characteristic of L-Proline. The wagging and rocking of CH2 is
1331 cm-1 and 840 cm-1. The peak at 1050 cm-1 is assigned to the C-N stretching vibrations.
The NMR spectral analysis is the important analytical technique used to the study of
the structure of organic compounds. The 1H and 13C NMR spectrum of DBPC was recorded
using D2O as solvent on a Bruker 300MHz (Ultra shield) TM instrument at 23 °C (300 MHz
for 1H NMR and 75 MHz for 13C NMR) to confirm the molecular structure. In the present
investigation, the 1H and 13C NMR spectra were recorded to confirm the molecular structure.
The proton NMR spectrum is shown in Fig.4 (a). In proton NMR spectrum, the CH2 (a)
proton appears as a multiplet centred at δ 1.64 ppm in the aliphatic region of the spectrum.
The multiplet protons signal appearing at δ 1.95 ppm has been assigned for the CH2 (b)
protons. The signal corresponding to CH2 (c) protons of the pyrrolidine ring is appearing as a
triplet centred at δ 2.80 ppm. The signal due to CH2 (d) protons is shifted to higher δ values
as a consequence of the electron withdrawing carbonyl group in the vicinity and appears as a
triplet at δ 4.08 ppm. The sharp singlet around δ 4.7 ppm is attributed to the presence of D2O.
The 13C chemical shift appearing at δ174 ppm confirms the presence of carboxylate
5
functional group in L-Proline (COO-) and the presence of aliphatic carbon chemical shift is at
δ 23.82, 29.00 ppm and 46.00 ppm (CH2). The conformation of another aliphatic carbon
appears at δ 61 ppm (CH). The 13C spectrum is shown in Fig.4 (b).
3.2. Single crystal X-ray diffraction
The single crystal X-ray diffraction studies of DBPC were performed using Bruker
AXS Kappa APEX II CCD Diffractometer equipped with graphite monochromated Mo Kα
radiation (λ=0.71073 Å) at room temperature. The single crystal of size 0.3 x 0.2 x 0.25 mm3
was used for the study. Accurate unit cell parameters were determined from the reflections of
36 frames measured in three different crystallographic zones by the method of difference
vectors. Data collection, data reduction and absorption correction were performed by APEX2,
SAINT-plus and SADABS programs [23]. The crystallographic data and the refinement
details for DBPC are summarized in Table .1. A total of 8771 reflections were recorded
with 2θ range 2.32 º to 28.79 º of which 3065 reflections are considered as unique reflections
with I > 2σ(I). The structure was solved by direct methods procedure using SHELXS-97
program and refined by Full-matrix least squares procedure on F2 using SHELXL-97
program [24]. The final refinement converges to R-values of R1= 0.0210 and WR2 = 0.0434.
Complex DBPC crystallizes in orthorhombic crystal system with P212121 space
group. The complex has a very similar structure to that of CdCl2 (Hpro); it consists of a one
dimensional polymer bridged by bromine atoms and carboxyl oxygen atoms. The Cd (II)
coordinates with two bromine atoms and two carboxyl oxygen atoms of two L-Proline
ligands: each of them is zwitter ionic. The carbon atom C4 of the pyrrolidine ring is
disordered over two positions with site occupancies of 0.546(7) and 0.454(7) respectively.
The coordination environment around the Cd atom, involving Br atoms and carboxyl
O atoms, may be visualized as a distorted tetrahedral as shown in the ORTEP view (Fig. 5).
The coordination of two bromine atoms with cadmium are of different bond length Cd (1)-Br
6
(2) [2.6051(4) A°], Cd (1)-Br (1) [2.5345(5) A°]. These are due to torsion bending of
pyrrolidine ring. The carboxylate groups in compound DBPC are not planar with the
pyrrolidine ring as shown in the torsion angle of O(2)-C(1)-O(1)-Cd(1), O(4)-C(6)-O(3)-
Cd(1), which are -18.5(5)º, 8.2 (4)º respectively. The packing arrangement of the molecule
viewed down in the c-axis is shown in Fig.6. The metal ligand coordination and molecular
geometry are similar to that observed in related amino acid containing compounds [11-13].
The selected bond lengths and angles of DBPC are listed in Table.2. and Table .3.
The hydrogen bond is the most important of all directional intermolecular
interactions. The corresponding data for the H-bonds are listed in Table.4. The molecular
arrangement in the crystal is mainly decided by N-H…O and N-H…Br hydrogen bonds.
The hydrogen bonds N2-H2A…Br (2) [-x+2, y-1/2,-z+1/2] and N2-H2B…O1[x+1, y, z]
interconnect the molecular complex to generate a two dimensional supramolecular network
extending parallel to (0 0 1) plane. Parallel stacking of (0 0 1) two dimensional network along
c-axis is further interlinked through NI-H1B…O2 and N1-H1A…Br1 [x-1/2,-y+1/2,-z]
hydrogen bonds building a three dimensional supramolecular network, which constitutes the
molecular packing of the crystal.
3.3. UV-Vis-NIR spectral analysis
The UV–Vis–NIR spectrum was analysed by Perkin-Elmer Lambda35 spectrometer
with (DBPC) single crystal in the range of 200–1100 nm. The transmission range is important
for any NLO material because it can be of practical use only if it has wide transparency
window. A transparent crystal of 2 mm thickness was used for this measurement. The grown
DBPC crystal has 42% of transparency and UV cut-off wavelength at 235 nm, due
π π* transition in the complex. The transmission spectrum is depicted in Fig.7. The
absence of absorption in the visible range might be due to the filled d 10 orbital of the metal
ion in the complex [25].
7
3.4. Magnetic studies
Magnetic properties were measured using a Vibrating Sample Magnetometer (VSM)
(Lake Shore 7410). Magnetic measurements were carried out on crystalline sample of DBPC
at room temperature. The hysteresis loop of the magnetization versus the magnetic field
strength is shown in Fig.8. The Zn (II), Cd (II) metal complexes possess diamagnetic
properties but some metal coordinated complexes may possess different properties. This
hysteresis looping occurs due to the path dependence of the material response to an external
magnetic field. Crystalline sample of 0.060 g of DBPC with applied field of 15.001×10+3 G
shows that the saturation magnetization (Ms), the remnant magnetization (Mr), retentivity
and coercivity (Hc) are 558.12 ×10-6 emu/g, 368.58×10-9 emu/g, 6.35 ×10-6 emu and
309.81G respectively. The field when the hysteresis loop passes through a zero in
magnetization is called the coercivity of the sample [26–29]. Materials referred to as ‘soft’
have a relatively low coercivity close to zero. This results in a hysteresis loop for soft
materials which would more resemble a single, ‘S’ shaped, curved path passing through the
origin. The coordination environments are changed from tetrahedral to distorted tetrahedral
structure (diamagnetic to soft magnetic nature). The weak interactions of N-H....O, N-H....Br
hydrogen bondings are also responsible for such kind of magnetic properties [30-33].
3.5. Thermal analysis
The TG/DTA of (DBPC) has been recorded by using PerkinElmer Diamond TG/DTA
instrument. A platinum crucible was used for heating the sample and analysis was carried out
in an atmosphere of nitrogen at a heating rate of 10°C/min in the temperature range of
30–450 °C. The initial mass of the material subjected to the analysis was 2.86 mg. The
TG/DTA is shown in the Fig.9. From the TG curve it is understood that the material is stable
up to 218 ºC and on further heating the material suffers weight loss and it follows one stage
weight loss pattern. Only one major weight loss of about 40 % exists in the TGA curve
8
between 220 ºC and 340 ºC. In DTA curve, the sharp endothermic peak at 226 °C is due to
decomposition point of the complex crystals. The sharpness of this endothermic peak shows
good degree of crystallinity and purity of the material and another endothermic peak appears
at 334 ºC. This is due to some complexation in the remaining melt. There is no endothermic
or exothermic peak upto 210 ºC in DTA curve, whereas TGA shows the 40 % weight loss
upto 340 ºC. Hence it is clear that the material is stable upto 218 ºC making it suitable for
possible application in lasers, where the crystal is required to withstand high temperatures.
3.6. Vickers micro hardness measurement
Hardness is a measure of material’s resistance to localized plastic deformation. It
plays a key role in device fabrication. Vickers micro-hardness measurement has been
performed on (DBPC) crystal using MATSUZAWA model MMT-X series micro hardness
tester fitted with diamond indenter. The dwell time was 5 s for all the loads. The indentations
were made using a Vickers pyramidal indenter for loads 1 to 100g. Vickers micro hardness
number (Hv) is evaluated from the relation
Hv = 1.8544P/d2 kg/mm2
where P is the applied load in g and d is the diagonal length of the impression in mm. The
variation in microhardness values with applied load is shown in Fig.10. From Vickers
microhardness studies, it is observed that the hardness value increases up to a load of 100 g.
For load above 100 g cracks developed around the indentation mark, which may be due to the
release of internal stresses.
3.7. Second harmonic studies
Kurtz and Perry [34] second harmonic generation (SHG) test was performed to find
the NLO property of DBPC crystal. A Q-switched Nd: YAG laser was used as light source.
A laser beam of fundamental wavelength 1064 nm, 8 ns pulse width with 10 Hz pulse rate
was made to fall normally on the sample cell. Powdered samples of standard KDP and
9
compound DBPC with the same particle size were considered for powder SHG
measurements. KDP crystal was used as the reference material in the SHG measurement.
The SHG efficiency for DBPC for 2.25 times that of KDP. The SHG measurements on the
crystal of DBPC indicate the potential application of the material for frequency conversion
process.
4. Conclusion
Single crystals of dibromo bis (l-proline) Cd (II) were grown from slow evaporation
solution technique. FT-IR and NMR spectroscopic studies confirm the formation of the
dibromo bis (l-proline) Cd (II) coordinated complex. Single crystal X-ray diffraction analysis
revealed that the compound crystallizes in an orthorhombic system with non-centro
symmetric space group P212121. The grown crystals are transparent in the entire visible
region. The magnetic study reveals that DBPC crystal has soft magnetic property. Thermal
analysis reveals that the material is stable up to 218 ºC. Microhardness study revealed that
the material is stable up to 100 g of load. The second harmonic generation efficiency of
DBPC was 2.25 times that of KDP crystal.
Supplementary information
The crystallographic data of DBPC has been deposited with the Cambridge
Crystallographic Data Centre [CCDC No. 926963]. Copies of the data can be obtained free of
charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge
Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 0
1223 336 033; email: deposit@ccdc.cam.ac.uk].
Acknowledgement
One of the authors (K. Boopathi) is grateful to the SSN Institution for the award of Junior Research Fellowship.
10
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(1985) 1592.
[14] K. Li, P.Yang, D. Xue, Acta Materialia, 60 (2012) 35-42
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11
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[19] S. Boomadevi, R. Dhanasekaran, J. Cryst. Growth, 261 (2004) 70.
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R. Mohan, Cryst. Growth Des. 7 (2007) 183.
[22] M. Fleck, P. Held, K. Schwendtner, Bohaty, Z. Krist., 223 (2008)212.
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[23] Bruker (2004).APEX2 and SAINT-Plus. Bruker AXS Inc. Madison, Wisconsin, USA.
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12
Figure captions
Fig.1. Reaction scheme of DBPC
Fig.2. As grown single crystals of DBPC
Fig.3. FT-IR spectrum of DBPC crystal
Fig.4. (a) 1H NMR spectrum of DBPC (b) 13C NMR spectrum of DBPC
Fig.5. ORTEP view of the molecule with displacement ellipsoids drawn at 40%
Fig.6. Packing arrangements of molecule viewed down the c- axis
Fig.7. UV- visible-NIR transmittance spectrum DBPC crystal
Fig.8. Hysteresis curve of DBPC crystal
Fig.9. TGA and DTA curve of DBPC crystal
Fig.10. Variation of micro hardness number with load
13
HN O
OH
L-proline Cadmium bromide
Cd Br22 H2O
N
C
OO
N
C
O O
CdBr
Br
H
H
H
H
Dibromobis (L-proline) Cd (II)
Fig.1. Reaction scheme of DBPC
Fig.2. As grown single crystals of DBPC
14
4000 3500 3000 2500 2000 1500 1000 500
0
20
40
60
80
100
840
995
937
781
49067
059
4
1050
1082
1161
1190
1259
1331
1415
1538
1633
2564
2434
2564
2732
3028
3465
% t
rans
mit
tanc
e
Wave number (cm-1)
Fig.3. FT-IR spectrum of DBPC crystal
Fi
Fig
ig.4
g.4
4. (a
. (b
a) 1H
b) 13
H N
3C N
NM
NM
15
MR s
MR
d
5
spe
spe
ectru
ectr
c
um
rum
of
m of
b
a
DB
f DB
BPC
BPC
C
C
16
Fig.5. ORTEP view of the molecule with displacement ellipsoids drawn at 40%.
Fig.6. Packing arrangements of molecule viewed down the c- axis
17
Fig.7. UV- visible-NIR transmittance spectrum DBPC crystal
Fig.8. Hysteresis data of DBPC
200 400 600 800 1000
0
10
20
30
40
50
% o
f tra
nsm
itta
nce
Wave length (nm)
-15000 -10000 -5000 0 5000 10000 15000
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
moment(emu)
Field (G)
18
0 100 200 300 400 50050
60
70
80
90
100
110
TGA DTA
Temperature (0C)
Wei
ght
(%)
226.07 oC
334.93 oC
218 oC
-25
-20
-15
-10
-5
0
5
Hea
t fl
ow (
mW
/g)
Fig.9. TGA and DTA curve of DBPC
0 20 40 60 80 100 1205
10
15
20
25
30
35
40
Har
dnes
s nu
mbe
r (k
g/m
m2 )
Load (P)
Fig.10. Variation of micro hardness number with load
19
Table 1: Crystal data and structure refinement for DBPC
Empirical formula C10 H18 Br2 Cd N2 O4
Formula weight 502.48
Temperature 293(2) K
Wavelength 0.71073 A
Crystal system, space group Orthorhombic, P212121
Unit cell dimensions a = 6.7408(3) A alpha = 90 deg.
b = 14.1848(8) A beta = 90 deg.
c = 16.3546(9) A gamma = 90 deg.
Volume 1563.78(14) A^3
Z, Calculated density 4, 2.134 Mg/m^3
Absorption coefficient 6.516 mm^-1
F(000) 968
Crystal size 0.30 x 0.25 x 0.20 mm
Theta range for data collection 2.49 to 26.00 deg.
Limiting indices -5<=h<=8, -17<=k<=17, -20<=l<=17
Reflections collected / unique 8771 / 3065 [R(int) = 0.0248]
Completeness to theta = 26.00 99.90%
Absorption correction Semi-empirical from equivalents
Max. and min. transmission 0.3556 and 0.2453
Refinement method Full-matrix least-squares on F^2
Data / restraints / parameters 3065 / 7 / 193
Goodness-of-fit on F^2 0.922
Final R indices [I>2sigma(I)] R1 = 0.0210, wR2 = 0.0434
R indices (all data) R1 = 0.0266, wR2 = 0.0451
Absolute structure parameter 0.003(7)
Extinction coefficient 0.0044(2)
Largest diff. peak and hole 0.287 and -0.298 e.A^-3
Table.2. Bond lengths [A] for DBPC
20
Band length [A]
C(1)-O(2) 1.224(4)
C(1)-O(1) 1.269(4)
C(1)-C(2) 1.508(4)
C(2)-N(1) 1.510(5)
C(2)-C(3) 1.523(5)
C(2)-H(2) 0.9800
C(3)-C(4) 1.486(8)
C(3)-C(4') 1.512(7)
C(3)-H(3A) 0.9700
C(3)-H(3B) 0.9700
C(3)-H(3C) 0.9700
C(3)-H(3D) 0.9700
C(4)-C(5) 1.461(9)
C(4)-H(4A) 0.9700
C(4)-H(4B) 0.9700
C(4)-H(5D) 1.5877
C(4')-C(5) 1.426(7)
C(4')-H(4C) 0.9700
C(4')-H(4D) 0.9700
C(5)-N(1) 1.475(5)
C(5)-H(5A) 0.9700
C(5)-H(5B) 0.9700
C(5)-H(5C) 0.9700
C(5)-H(5D) 0.9700
C(6)-O(4) 1.214(4)
C(6)-O(3) 1.256(4)
C(6)-C(7) 1.520(5)
C(7)-N(2) 1.499(4)
C(7)-C(8) 1.511(5)
C(7)-H(7) 0.9800
C(8)-C(9) 1.489(6)
C(8)- H(8A) 0.9700
C(8)-H(8B) 0.9700
C(9)-C(10) 1.499(6)
C(9)-H(9A) 0.9700
C(9)-H(9B) 0.9700
C(10)-N(2) 1.488(5)
C(10)-H(10A) 0.9700
C(10)-H(10B) 0.9700
N(1)-H(1B) 0.901(10)
N(1)-H(1A) 0.897(10)
N(2)-H(2A) 0.906(10)
N(2)-H(2B) 0.901(10)
O(1)-Cd(1) 2.214(2)
O(3)-Cd(1) 2.188(3)
Cd(1)-Br(1) 2.5345(5)
Cd(1)-Br(2) 2.6051(4)
21
Table.3. Bond angles [deg] for DBPC
Band angle [deg]
O(2)-C(1)-O(1) 125.5(3)
O(2)-C(1)-C(2) 120.3(3)
O(1)-C(1)-C(2) 114.2(3)
C(1)-C(2)-N(1) 108.8(3)
C(1)-C(2)-C(3) 112.5(3)
N(1)-C(2)-C(3) 103.9(3)
C(1)-C(2)-H(2) 110.5
N(1)-C(2)-H(2) 110.5
C(3)-C(2)-H(2) 110.5
C(4)-C(3)-C(4') 33.3(4)
C(4)-C(3)-C(2) 106.2(4)
C(4')-C(3)-C(2) 105.3(4)
C(4)-C(3)-H(3A) 110.5
C(4')-C(3)-H(3A) 136.3
C(2)-C(3)-H(3A) 110.5
C(4)-C(3)-H(3B) 110.5
C(4')-C(3)-H(3B) 80.4
C(2)-C(3)-H(3B) 110.5
H(3A)-C(3)-H(3B) 108.7
C(4)-C(3)-H(3C) 79.6
C(4')-C(3)-H(3C) 110.4
C(2)-C(3)-H(3C) 110.9
H(3A)-C(3)-H(3C) 32.7
H(3B)-C(3)-H(3C) 132.1
C(4)-C(3)-H(3D) 135.4
C(4')-C(3)-H(3D) 110.8
C(2)-C(3)-H(3D) 110.6
H(3A)-C(3)-H(3D) 79.2
H(3B)-C(3)-H(3D) 32.2
N(1)-C(5)-H(5C) 110.4
H(5A)-C(5)-H(5C) 33.6
H(3C)-C(3)-H(3D) 108.8
C(5)-C(4)-C(3) 106.2(5)
C(5)-C(4)-H(4A) 110.5
C(3)-C(4)-H(4A) 110.5
C(5)-C(4)-H(4B) 110.5
C(3)-C(4)-H(4B) 110.5
H(4A)-C(4)-H(4B) 108.7
C(5)-C(4)-H(5D) 36.8
C(3)-C(4)-H(5D) 129.7
H(4A)-C(4)-H(5D) 75.0
H(4B)-C(4)-H(5D) 114.6
C(5)-C(4')-C(3) 106.6(4)
C(5)-C(4')-H(4C) 110.4
C(3)-C(4')-H(4C) 110.4
C(5)-C(4')-H(4D) 110.4
C(3)-C(4')-H(4D) 110.4
H(4C)-C(4')-H(4D) 108.6
C(4')-C(5)-C(4) 34.6(4)
C(4')-C(5)-N(1) 106.1(4)
C(4)-C(5)-N(1) 106.3(4)
C(4')-C(5)-H(5A) 78.8
C(4)-C(5)-H(5A) 110.5
N(1)-C(5)-H(5A) 110.5
C(4')-C(5)-H(5B) 136.4
C(4)-C(5)-H(5B) 110.5
N(1)-C(5)-H(5B) 110.5
H(5A)-C(5)-H(5B) 108.7
C(4')-C(5)-H(5C) 110.5
C(4)-C(5)-H(5C) 136.2
C(10)-C(9)-H(9B) 110.9
H(9A)-C(9)-H(9B) 108.9
22
H(5B)-C(5)-H(5C) 78.0
C(4')-C(5)-H(5D) 110.5
C(4)-C(5)-H(5D) 78.7
N(1)-C(5)-H(5D) 110.7
H(5A)-C(5)-H(5D) 132.8
H(5B)-C(5)-H(5D) 33.7
H(5C)-C(5)-H(5D) 108.7
O(4)-C(6)-O(3) 126.1(3)
O(4)-C(6)-C(7) 119.9(3)
O(3)-C(6)-C(7) 113.9(3)
N(2)-C(7)-C(8) 104.8(3)
N(2)-C(7)-C(6) 111.1(3)
C(8)-C(7)-C(6) 117.7(3)
N(2)-C(7)-H(7) 107.6
C(8)-C(7)-H(7) 107.6
C(6)-C(7)-H(7) 107.6
C(9)-C(8)-C(7) 103.5(3)
C(9)-C(8)-H(8A) 111.1
C(7)-C(8)-H(8A) 111.1
C(9)-C(8)-H(8B) 111.1
C(7)-C(8)-H(8B) 111.1
H(8A)-C(8)-H(8B) 109.0
C(8)-C(9)-C(10) 104.4(3)
C(8)-C(9)-H(9A) 110.9
C(10)-C(9)-H(9A) 110.9
C(8)-C(9)-H(9B) 110.9
N(2)-C(10)-C(9) 104.6(3)
N(2)-C(10)-H(10A) 110.8
C(9)-C(10)-H(10A) 110.8
N(2)-C(10)-H(10B) 110.8
C(9)-C(10)-H(10B) 110.8
H(10A)-C(10)-H(10B) 108.9
C(5)-N(1)-C(2) 108.9(3)
C(5)-N(1)-H(1B) 118(3)
C(2)-N(1)-H(1B) 101(3)
C(5)-N(1)-H(1A) 113(3)
C(2)-N(1)-H(1A) 104(3)
H(1B)-N(1)-H(1A) 111(4)
C(10)-N(2)-C(7) 108.0(3)
C(10)-N(2)-H(2A) 110(4)
C(7)-N(2)-H(2A) 103(4)
C(10)-N(2)-H(2B) 107(3)
C(7)-N(2)-H(2B) 115(3)
H(2A)-N(2)-H(2B) 113(4)
C(1)-O(1)-Cd(1) 115.3(2)
C(6)-O(3)-Cd(1) 105.9(2)
O(3)-Cd(1)-O(1) 93.25(10)
O(3)-Cd(1)-Br(1) 128.08(7)
O(1)-Cd(1)-Br(1) 125.05(7)
O(3)-Cd(1)-Br(2) 99.26(7)
O(1)-Cd(1)-Br(2) 97.19(6)
Br(1)-Cd(1)-Br(2) 107.758(15)
23
Table.4. Hydrogen bonds for DBPC [A and deg.].
Symmetry transformations used to generate equivalent atoms:
a -x+2, y-1/2,-z+1/2 b x+1, y, z c x-1/2,-y+1/2,-z
D-H...A d(D-H) d(H...A) d(D...A) <(DHA)
N(2)-H(2A)...Br(2)a 0.906(10) 2.362(15) 3.257(3) 170(5)
N(2)-H(2B)...O(1)b 0.901(10) 2.01(2) 2.843(4) 152(4)
N(1)-H(1B)...O(2) 0.901(10) 2.07(4) 2.661(4) 122(4)
N(1)-H(1A)...Br(1)c 0.897(10) 2.64(3) 3.448(3) 150(4)
24
Graphical Abstract
25
Highlights
• Good quality single crystals of dibromo bis (l-proline) Cd (II) in an orthorhombic
system with P212121 were grown.
• Metal–ligand coordination, structural properties and hydrogen bonds are discussed.
• At room temperature DBPC possess soft magnetic properties
• DBPC crystal is thermally stable up to 218 ˚C
• SHG efficiency of the DBPC is 2.25 times that of KDP crystal
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