synthesis and structural characterization of mixed ligand...
TRANSCRIPT
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SYNTHESIS AND STRUCTURAL
CHARACTERIZATION OF MIXED LIGAND
COMPLEXES OF COPPER(II) WITH DIAMINES
AND CARBOXYLATES
Submitted By:
SYEDA SHAHZADI BATOOL
2009-Ph. D. Chemistry-05
Supervised By:
Prof. Dr. SYEDA RUBINA GILANI
DEPARTMENT OF CHEMISRTY UNIVERSITY OF ENGINEERING AND TECHNOLOGY
LAHORE-PAKISTAN
2016
SYNTHESIS AND STRUCTURAL
CHARACTERIZATION OF MIXED LIGAND
COMPLEXES OF COPPER(II) WITH DIAMINES
AND CARBOXYLATES
Submitted By:
SYEDA SHAHZADI BATOOL
2009-Ph. D. Chemistry-05
Supervised By:
Prof. Dr. SYEDA RUBINA GILANI
DEPARTMENT OF CHEMISRTY UNIVERSITY OF ENGINEERING AND TECHNOLOGY
LAHORE-PAKISTAN
2017
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SYNTHESIS AND STRUCTURAL CHARACTERIZATION
OF MIXED LIGAND COMPLEXES OF COPPER(II) WITH
DIAMINES AND CARBOXYLATES
A Research Thesis Submitted
To
The University of Engineering & Technology Lahore
In
Partial fulfillment of the Requirements for the Degree
Of
Doctorate of philosophy
In
Chemistry
By
SYEDA SHAHZADI BATOOL 2009-Ph.D-Chemistry-05
DEPARTMENT OF CHEMISRTY UNIVERSITY OF ENGINEERING AND TECHNOLOGY
LAHORE-PAKISTAN
2017
This thesis has been evaluated by the following examiners
External Examiners
From Abroad
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i) Dr. Sc. Christian Betzel,
Institute of Biochemistry and molecular biology
Martin-Luther-King Platz 6, 20146 Hamburg.
ii) Dr. Liu Qingguan,
School of Chemistry & Chemical Engineering,
Key Laboratory of Theoretical Chemistry, Ministry of Education,
Human University of Science & Technology,
Xiargtan 411201, China.
iii) Prof. Dr. Mitu Liviu,
Department of Physics & Chemistry,
University of Pitesti, Pitesti, Romania.
b) From Pakistan
Prof. Dr. Ahmad Adnan,
Chairman, Department of Chemistry, GCU, Lahore, Pakistan.
Assoc. Prof. Dr. Muhammad Akhyar furrukh,
Department of Chemistry, GCU, Lahore, Pakistan.
Internal Examiner:
Prof. Dr. Syeda Rubina Gilani,
Chairperson, Department of Chemistry, UET, Lahore, Pakistan.
DEPARTMENT OF CHEMISTRY
UNIVERSITY OF ENGINERING AND TECHNOLOGY
LAHORE
Declaration
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I “SYEDA SHAHZADI BATOOL” declare that the thesis titled: “SYNTHESIS AND
STRUCTURAL CHARACTERIZATION OF MIXED LIGAND COMPLEXES OF
COPPER(II) WITH DIAMINES AND CARBOXYLATES”, is my own research
work. This thesis is being submitted for partial fulfillment of the requirements for the
degree of Ph.D. in chemistry. The thesis contains no material that has been accepted and
published previously for the award of any degree.
____________________ _________
Signature of Candidate Date
I approve that the above titled thesis can be submitted for the examination.
____________________ _________
Signature of Supervisor Date
DEDICATIONS
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Dedicated to
My parents,
My Children,
And my loving family members
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ACKNOWLEDGEMENTS
All praises, deepest thanks and gratitude to Almighty Allah, Who bestowed me with all his
blessings, and gave me enough strength to complete my Ph. D. research work. Peace and
blessings of Allah be upon His Holy Prophet Hazrat Muhammad (PBUH), and his progeny,
who enlightened the path of knowledge and guidance for mankind. In my diligent endeavor in
the pursuit of completion of the researh work, I was lucky to have support of a large number of
people to whom I owe my gratitude.
First of all, I wish to express fervent sense of thankfulness to my mentor and thesis
advisor, Prof. Dr. Syeda Rubina Gilani, Chairperson, Department of Chemistry, University of
Engineering and Technology, Lahore. I shall always be grateful for her inspiring guidance,
encouragement, dedication to excellence in teaching and research, her dynamic supervision
and most importantly, for giving me the honor to be her student, after the resignation of my ex-
supervisor, Dr. Saeed Ahmad. Although his untimely departure affected us a lot, but I would
not forget to acknowledge his efforts in help making me a scientist than a mere experimentalist.
At the same time, I extend my gratitude to Dr. Asif Ali Qaiser, Chairman, Polymer Department,
for allowing me to conduct FTIR analyses of my samples, and Prof. Dr. M. Nawaz Tahir,
University of Sargodha, for single crystal X-ray analyses. I am grateful to Dr. Qurat-ul-ain
Syed, FBRC department, PCSIR laboratories, Lahore, Pakistan, for allowing me to perform
antibacterial studies in her supervision. A special word of gratitude is due to Dr. William T. A.
Harrison for structure solution and structure analyses. I am thankful to all faculty and staff
members for being a source of scholarly guidance in my studies. A special word of thanks is
due to all working staff for always being helpful. I also express my deepest gratitude from the
core of my heart, for the Higher Education Commission, Islamabad, for providing financial
support through Indigenous 5000 Fellowship Program.
Lastly, I wonder if I would be able to find words to express my deepest feelings of love
and compassion for my beloved mother, as it is due to her untiring efforts, that I am now able
to complete my research work. My children Syeda Sakina Zainab, Syed Muhammad Abbas and
Syed Muhammad Mehdi are the joys of my life through whose love and affection, I am able to
accomplish this uphill task.
Syeda Shahzadi Batool
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ABSTRACT
This research work presents one pot synthesis of ternary copper(II) carboxylates of N,N-
chelating diamine ligands. The carboxylate ligands used were sodium salts of benzoic acid,
2-chlorobenzoic acid, cinnamic acid, succinic acid, phthalic acid, terephthalic acid, 4-
aminobenzoic acid, 3-aminobenzoic acid, mefenamic acid, acetyl salicylic acid, and tartaric
acid. The N,N-chelating diamines utilized include N,N,N′,N′-tetramethylethylenediamine
(tmen), while some complexes of carboxylates with ethylenediamine (en), 1,10–
phenanthroline (phen) and 2,2′–bipyridine (bipy) have also been prepared. The structural
aspects and geometrical assignments related to the synthesized complexes have been
investigated with the help of analytical techniques like FT-IR, UV-Visible spectroscopy,
thermal studies (TGA) and single crystal X-ray diffraction analysis. The investigated ternary
copper(II) complexes involving N,N,N′,N′-tetramethylethylenediamine (tmen) include
[Cu(tmen)(BA)2(H2O)2], (1a), [Cu(tmen)(salH)2(H2O)] (2a), {[Cu(tmen)(mef)2] (3a),
[Cu(tmen)(pABA)2]. 1/2 MeOH) (4a), [Cu(tmen)(o-ClBA)2] (5a), [Cu(tmen)(cinn)2]. H2O
(6a), [Cu(tmen)(phtH)2] (7a), [Cu(tmen)(tpht)(H2O)2]n (8a), {[Cu(tmen)(succin)]n.4H2O}
(9a), {[Cu(tmen)(tart)]·2H2O}n (10a). Single crystal analyses of the prepared complexes have
revealed that most of the Cu(II)-N,N,N′,N′-tetramethylethylenediamine adducts with the
carboxylate ligands are mononuclear, in which N,N,N′,N′-tetramethylethylenediamine is
coordinated to Cu(II) in an invariably chelating bidentate mode. In these complexes, the
carboxylate moiety belonging to a carboxylate ligand is coordinated to the central Cu(II) ion,
either in a monodentate (1a, 2a, 4a, 7a), or bidentate (3a, 5a, 6a) fashion. These
mononuclear complexes can be; four-coordinate (4a), with a square planar environment,
five-coordinate (2a, 7a),with a square pyramidal geometry, or six-coordinate (1a, 3a, 5a, 6a )
with an octahedral coordination geometry. Three complexes of Cu-tmen-carboxylato series
are polynuclear in nature (8a, 9a, 10a) and adopt an octahedral coordination environment.
The carboxylate functionality varies in coordination modes, from bis-monodentate bridging
(8a) to chelating bridging (9a-10a).
Another mixed ligand copper(II) complex incorporating ethylenediamine and salicylate
[Cu(en)(salH)Cl]n (where en= ethylenediamine, salH1- = (salicylate1-) (11a) has also been
synthesized. The complex [Cu(en)(salH)Cl]n (11a) is found to be unprecedented because of
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the presence of [Cu-Cl]n back-bone formed by central Cu(II) ion and bridging Cl atoms, also
it had both ethylenediamine and salicylic acid as a part of the inner coordination sphere,
while in most of the known examples, carboxylates usually are found lying uncoordinated in
the outer sphere.
Two ternary copper(II) carboxylate complexes, containing 2,2 ′-bipyridine (bipy = C10H8N2)
having the formulae [Cu(bipy)(cinn)2(H2O)] (1b) [Cu2(bipy)2(pABA)3(pABAH)]. Cl. 3H2O
(2b) {(where cinn1- = cinnamate (C9H7O21-) anion, pABA1- = p-amino benzoate (C7H6NO21-)
anion, and pABAH = p-amino benzoic acid (C7H7NO2)} have been prepared and
characterized. The mononuclear ternary Cu(II) complex incorporating 2,2′–bipyridine and
cinnamate as shown by single crystal X-ray analyses is found to be square pyramidal, formed
by the coordination of bidentate 2,2′–bipyridine, and two monodentate carboxylate groups
from two cinnamates, while the apical position is occupied by an aqua-O atom. The second
dinuclear mixed ligand Cu(II) complex of 2,2′–bipyridine and p-aminobenzoate (1b) is also
found to be unique. It has two copper(II) centers in square pyramidal environments, which
are interlinked by two bridging p-aminobenzoates and by two 2,2′–bipyridine ligands in a
chelating mode. One remaining p-aminobenzoate is attached through its carboxylato-O atom
in a traditional monodentate mode, while the other pABAH is attached to copper(II) through
its N atom.
Two novel mixed ligand copper(II)-phen based carboxylate complexes represented as
[Cu(phen)(benzoate)2] 1c, and [Cu(phen)(m-amb)Cl·½H2O] 2c (where phen = 1,10-
phenanthroline, BA1- = benzoate, m-ABA1- = m-aminobenzoate) have been synthesized and
characterized. The geometry and structure of the mononuclear ternary Cu(II) complex
incorporating 1,10–phenanthroline and m-aminobenzoate, as confirmed through single
crystal X-ray analyses is found to be square pyramidal, formed by the coordination of
chelating 1,10–phenanthroline, a chelating m-aminobenzoate, while the apical position is
occupied by a Cl atom. The second monomeric complex [Cu(phen)(benzoate)2] was square
planar, with one bidentate phen and two monodentate benzoates.
Antimicrobial studies of complexes have also been performed. Some of these copper(II)
complexes are found to be biologically active against bacteria.
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TABLE OF CONTENTS
Acknowledgement i
Abstract ii
Table of contents iv
List of tables x
List of figures xii
List of Schemes xvi
List of abbreviations xvii
Chapter-1 INTRODUCTION 1
1.1 Chemistry of copper 1
1.2 Chemistry of copper(II) 3
1.2.1 General metabolic functions of copper 3
1.3 Biological activities of copper complexes 4
1.4 Metal carboxylate chemistry and their coordination modes 5
1.5 Structures and molecular geometries of copper (II)-carboxylate complexes 7
1.5.1 Geometries of mononuclear copper(II) complexes 7
1.5.1.1 Four-coordinate complexes 8
1.5.1.2 Five-coordinate copper(II) complexes 9
1.5.1.3 Six-coordinate copper(II) complexes 9
1.5.2 Bi-nuclear copper(II) carboxylate complexes 10
1.5.3 Trinuclear copper(II) carboxylate complexes 12
1.5.4 Polynuclear copper(II) complexes 12
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1.6 Supra-molecular architectures based on copper(II) carboxylates: 13
1.7 The diamine ligands 14
1.8 Aims and Objectives 16
Chapter-2 LITERATURE REVIEW 17
Chapter-3 EXPERIMENTAL 27
3.1 Materials and methods 27
3.2 Single crystal X–ray structure determination of complexes 27
3.2.1 Single crystal X–ray structure determination of complexes 1a-11a 28
3.2.2 Single crystal X–ray structure determination of complexes 1b-2b 35
3.2.3 Single crystal X–ray structure determination of complexes 1c-2c 36
3.3 Antimicrobial activity measurement (Agar well diffusion method) 38
3.3.1 Antimicrobial activity of complexes 1a-11a 38
3.3.2 Antimicrobial activity of complexes 1b-2b 39
3.3.3 Antimicrobial activity of complexes 1c-2c 39
3.4 General procedures for the syntheses of complexes 40
3.4.1 General procedures for the syntheses of complexes 1a-11a 40
3.4.1.1 Synthesis of [Cu(tmen)(BA)2(H2O)2] (1a) 40
3.4.1.2 Synthesis of [Cu(tmen)(salH)2H2O] (2a) 41
3.4.1.3 Synthesis of [Cu(tmen)(mef)2] (3a) 42
3.4.1.4 Synthesis of [Cu(tmen)(pABA)2]. 1/2 MeOH) (4a) 42
3.4.1.5 Synthesis of [Cu(tmen)(o-ClBA)2] (5a) 43
3.4.1.6 Synthesis of [Cu(tmen)(cinn)2]. H2O (6a) 43
3.4.1.7 Synthesis of [Cu(tmen)(phtH)2] (7a) 44
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3.4.1.8 Synthesis of [Cu(tmen)(tpht)(H2O)2]n (8a) 45
3.4.1.9 Synthesis of [Cu(tmen)(succin)] .4H2O}n(9a) 45
3.4.1.10 Synthesis of {[Cu2(tmen)2(tart)2]·2H2O}n(10a) 45
3.4.1.11 Synthesis of [Cu(en)(salH)Cl]n(11a) 46
3.4.2 General procedures for the syntheses of complexes 1b-2b 47
3.4.2.1 Synthesis of [Cu(bipy)(cinn)2H2O] (1b) 47
3.4.2.1 Synthesis of Cu2(bipy)2(pABA)3(pABAH)]. Cl. 3H2O (2b) 48
3.4.3 General procedures for the syntheses of complexes 1c-2c 49
3.4.3.1 Synthesis of [Cu(phen)(benzoate)2] (1c) 49
3.4.3.2 Synthesis of [Cu(phen)(m-ABA)Cl].·½H2O (2c) 49
Chapter-4 RESULTS AND DISCUSSION 50
4.1 FTIR Spectroscopic Studies of Complexes 50
4.1.1 FTIR Spectroscopic Studies of Complexes 1a-11a 50
4.1.1.1 FTIR Studies of copper(II)-tmen complex (1) 52
4.1.1.2 FTIR Studies of [Cu(tmen)(BA)2(H2O)2] (1a) 52
4.1.1.3 FTIR Studies of [Cu(tmen)(salH)2H2O] (2a) 55
4.1.1.4 FTIR Studies of [Cu(tmen)(mef)2] (3a) 57
4.1.1.5 FTIR Studies of [Cu(tmen)(pABA)2].1/2 MeOH) (4a) 59
4.1.1.6 FTIR Studies of [Cu(tmen)(o-ClBA)2] (5a) 61
4.1.1.7 FTIR Studies of [Cu(tmen)(cinn)2]. H2O (6a) 63
4.1.1.8 FTIR Studies of [Cu(tmen)(phtH)2](7a) 65
4.1.1.9 FTIR Studies of [Cu(tmen)(tpht)(H2O)2]n(8a) 67
4.1.1.10 FTIR Studies of [Cu(tmen)(succin)] .4H2O}n (9a) 69
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4.1.1.11 FTIR Studies of {[Cu2(tmen)2(tart)2]·2H2O}n (10a) 71
4.1.1.12 FTIR Studies of [Cu(en)(salH)Cl]n (11a) 73
4.1.2 FTIR Spectroscopic Studies of Complexes 1b-2b 75
4.1.2.1 FTIR studies of Cu(II)-2,2′-bipyridine complex (2) 75
4.1.2.1 FTIR Studies of [Cu(bipy)(cinn)2H2O] (1b) 75
4.1.2.2 FTIR Studies of [Cu2(bipy)2(pABA)3(pABAH)]. Cl.3H2O (2b) 76
4.1.3 FTIR spectroscopic studies of complexes 1c-2c 81
4.1.3.1 FTIR Studies of [Cu(phen)(benzoate)2] (1c) 81
4.1.3.2 FTIR Studies of Cu(phen)(m-amb)Cl·½H2O (2c) 83
4.2 Uv-Visible spectroscopic studies of complexes 85
4.2.1 Uv-Visible spectroscopic studies of complexes 1a-11a 85
4.2.2 Uv-Visible spectroscopic studies of complexes 1b-2b 85
4.2.3 Uv-Visible spectroscopic studies of complexes 1c-2c 86
4.3 Thermal studies of complexes 87
4.3.1 Thermal studies of complexes 1a-11a 87
4.3.1.1 Thermal studies of [Cu(tmen)(BA)2(H2O)2] (1a) 87
4.3.1.2 Thermal studies of [Cu(tmen)(salH)2H2O] (2a) 88
4.3.1.3 Thermal studies of [Cu(tmen)(mef)2] (3a) 91
4.3.1.4 Thermal studies of [Cu(tmen)(pABA)2]. 1/2 MeOH) (4a) 91
4.3.1.5 Thermal studies of [Cu(tmen)(o-ClBA)2] (5a) 95
4.3.1.6 Thermal studies of [Cu(tmen)(cinn)2]. H2O (6a) 95
4.3.1.7 Thermal studies of [Cu(tmen)(phtH)2] (7a) 98
4.3.1.8 Thermal studies of [Cu(tmen)(tpht)(H2O)2]n 8a 98
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4.3.1.9 Thermal studies of [Cu(tmen)(succin)] .4H2O}n 9a 101
4.3.1.10 Thermal studies of {[Cu2(tmen)2(tart)2]·2H2O}n (10a) 101
4.3.2 Thermal studies of complexes 1b-2b 104
4.3.2.1 Thermal studies of [Cu(bipy)(cinn)2H2O] (1b) 104
4.3.2.2 Thermal studies of [Cu2(bipy)2(pABA)3(pABAH)]. Cl. S3H2O (2b) 105
4.3.3 Thermal studies of complexes 1c-2c 108
4.3.3.1 Thermal studies of [Cu(phen)(benzoate)2] (1c) 108
4.3.3.2 Thermal studies of Cu(phen)(m-amb)Cl·½H2O (2c) 108
4.4 X-ray Structure Description of Complexes 111
4.4.1 X-ray Structure Description of Complexes 1a-11a 111
4.4.1.1 X-ray Structure Description of complex (1a) 111
4.4.1.2 X-ray Structure Description of complex (2a) 115
4.4.1.3 X-ray Structure Description of complex (3a) 118
4.4.1.4 X-ray Structure Description of complex (4a) 121
4.4.1.5 X-ray Structure Description of complex (5a) 123
4.4.1.6 X-ray Structure Description of complex (6a) 126
4.4.1.7 X-ray Structure Description of complex (7a) 129
4.4.1.8 X-ray Structure Description of complex (8a) 132
4.4.1.9 X-ray Structure Description of complex (9a) 135
4.4.1.10 X-ray Structure Description of complex (10a) 138
4.4.1.11 X-ray Structure Description of complex (11a) 142
4.4.2 X-ray Structure Description of Complexes 1b-2b 145
4.4.2.1 X-ray Structure Description of complex (1b) 145
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4.4.2.2 X-ray Structure Description of complex (2b) 149
4.4.3 X-ray Structure Description of Complexes 1c-2c 154
4.4.3.1 X-ray Structure Description of complex (1c) 154
4.4.3.2 X-ray Structure Description of complex (2c) 157
4.5 Antimicrobial activity of complexes 160
4.5.1 Antimicrobial activity of complexes 1a-11a 160
4.5.2 Antimicrobial activity of complexes 1b-2b 161
4.5.3 Antimicrobial activity of complexes 1c-2c 161
CONCLUSIONS 164
FUTURE RESEACH WORKS 169
REFERENCES 170
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LIST OF TABLES
Table Title Page
1.1 Common oxidation states of copper with their coordination geometries 2
3.1 Structure refinement parameters of complexes 1a-2a 29
3.2 Structure refinement parameters of complexes 3a-4a 30
3.3 Structure refinement parameters of complexes 5a-6a 31
3.4 Structure refinement parameters of complexes 7a-8a 32
3.5 Structure refinement parameters of complexes 9a-10a 33
3.6 Structure refinement parameters of complex 11a 34
3.7 Structure refinement details for complexes 1b and 2b 35
3.8 Structure refinement parameters of the complexes 1c and 2c 37
4.1 Selected bond lengths (A˚) and angles (˚) for complex (1a) 114
4.2 Bond separations (Å) and bond angles (˚) in the complex (1a) 114
4.3 Selected bond lengths (Å) and angles (˚) for complex (2a) 116
4.4 Bond separations (Å) and bond angles (˚) in the complex (2a) 116
4.5 Selected geometric parameters (A˚, ˚) for (3a) 119
4.6 Bond separations (Å) and bond angles (˚) in the complex (3a) 119
4.7 Selected bond lengths (A˚) and angles (˚) for complex (4a) 121
4.8 Selected geometric parameters (A˚, ˚) for{[Cu(tmen)(Clba)2]·(5a) 125
4.9 Bond separations (Å) and bond angles (˚) in the complex (5a) 125
4.10 Selected bond lengths (A˚) and angles (˚) for complex (6a) 127
4.11 Bond separations (Å) and bond angles (˚) in the complex (6a) 127
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4.12 Selected bond lengths (A˚) and angles (˚) for complex (7a) 130
4.13 Bond separations (Å) and bond angles (˚) in the complex (7a) 130
4.14 Selected geometric parameters (A˚, ˚) for complex (8a) 133
4.15 Bond separations (Å) and bond angles (˚) in the complex (8a) 133
4.16 Selected bond lengths (A˚) and angles (˚) for complex (9a) 136
4.17 Bond separations (Å) and bond angles (˚) in the complex (9a) 136
4.18 Selected geometric parameters (A˚, ˚) for {[Cu2(tmen)2(tart)2]·2H2O}n (10a) 140
4.19 Selected geometric parameters (A˚, ˚) for [Cu(en)(salH)Cl]n(11a) 143
4.20 Bond separations (Å) and bond angles (˚) in the complex (11a) 143
4.21 Selected bond lengths (A˚) and angles (˚) for complex (1b) 148
4.22 Bond separations (Å) and bond angles (˚) in the complex (1b) 148
4.23 Selected bond lengths (Å) and angles (˚) for complex (2b) 152
4.24 Bond separations (Å) and bond angles (˚) in the complex (2b) 153
4.25 Selected bond distances (Å) and bond angles (o) for compounds (1c) 155
4.26 Selected bond lengths (Å) and angles (˚) for complex (2c) 158
4.27 Bond separations (Å) and bond angles (˚) in the complex (2c) 158
4.28 The antimicrobial activity data of complexes with inhibition zones (mm) against the
bacterial strains 162
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LIST OF FIGURES
Figure Title Page
1.1. Different coordination modes of metal carboxylates 6
1.2 Different lone pairs of metal carboxylates 6
1.3 Various bridging modes in metal carboxylates 7
1.4 Four-coordinate copper(II) complexes 8
1.5 Copper(II) complexes with square pyramidal geometry 9
1.6 Examples of complexes with octahedral geometry around copper(II) ion 10
1.7 X-ray structures of binuclear copper(II) carboxylates 11
1.8 X-ray structure of trinuclear complex [Cu3(dns)2(dnsH)2(H2O)4].4H2O 12
1.9 X-ray structures of polymeric copper(II) carboxylates 13
2.1 Copper(II) complexes of tmen with monocarboxylates 19
2.2 Copper(II) complexes of tmen with dicarboxylates 20
2.3 Copper(II) complexes of tmen with carboxylates 21
2.4 Structures of ternary copper(II)-bipy-carboxylates 24
2.5 Copper(II) complexes of phen with benzoate and 2-fluorobenzoate 25
4.1 FT-IR spectrum of copper(II)-tmen complex (1) 51
4.2 FT-IR spectrum of [Cu(tmen)(BA)2(H2O)2] (1a) 54
4.3 FT-IR spectrum of [Cu(tmen)(salH)2H2O] (2a) 56
4.4 FT-IR spectrum of [Cu(tmen)(mef)2] (3a) 58
4.5 FT-IR spectrum of [Cu(tmen)(pABA)2].1/2 MeOH) (4a) 60
4.6 FT-IR spectrum of [Cu(tmen)(o-ClBA)2] (5a) 62
4.7 FT-IR spectrum of [Cu(tmen)(cinn)2]. H2O (6a) 64
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4.8 FTIR spectrum of [Cu(tmen)(phtH)2] (7a) 66
4.9 FT-IR spectrum of [Cu(tmen)(tpht)(H2O)2]n (8a) 68
4.10 FT-IR spectrum of [Cu(tmen)(succin)] .4H2O}n (9a) 70
4.11 FT-IR spectrum of {[Cu(tmen)(tart)]·2H2O}n (10a) 72
4.12 FT-IR spectrum of [Cu(en)(salH)Cl]n (11a) 74
4.13 FT-IR spectrum of Cu(II)-2,2′-bipyridine complex (2) 78
4.14 FT-IR spectrum of [Cu(bipy)(cinn)2H2O] (1b) 79
4.15 FT-IR spectrum of [Cu2(bipy)2(pABA)3(pABAH)]. Cl. 3H2O (2b) 80
4.16 FT-IR spectrum of [Cu(phen)(benzoate)2] (1c) 82
4.17 FT-IR spectrum of [Cu(phen)(m-ABA)Cl[.·½H2O (2c) 84
4.18 Thermogram of [Cu(tmen)(BA)2(H2O)2] (1a) 89
4.19 Thermogram of [Cu(tmen)(salH)2 H2O] (2a) 90
4.20 Thermogram of [Cu(tmen)(mef)2] (3a) in N2 92
4.21 Thermogram of [Cu(tmen)(mef)2] (3a) in static air 93
4.22 Thermogram of [Cu(tmen)(pABA)2]. 1/2 MeOH) (4a) in N2 94
4.23 Thermogram of [Cu(tmen)(o-ClBA)2] (5a) in N2 96
4.24 Thermogram of [Cu(tmen)(cinn)2]. (H2O) (6a) 97
4.25 Thermogram of [Cu(tmen)(phtH)2] (7a) 99
4.26 Thermogram of [Cu(tmen)(tpht)(H2O)2]n (8a) 100
4.27 Thermogram of [Cu(tmen)(succin)]. 4H2O}n (9a) 102
4.28 Thermogram of {[Cu(tmen)(tart)]·2H2O}n (10a) 103
4.29 Thermogram of [Cu(bipy)2(cinn)(H2O)] (1b) 106
4.30 Thermogram of [Cu2(bipy)2(pABA)3(H-pABA)]. Cl. 3H2O (2b) 107
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4.31 Thermogram of [Cu(phen)(benzoate)2] (1c) 109
4.32 Thermogram of Thermogram of [Cu(phen)(m-ABA)Cl].·½H2O (2c) 110
4.33 ORTEP diagram (25 % ellipsoid probability) of the molecular structure of 1a 114
4.34 Selected part of the 1D chains of 1a 114
4.35 ORTEP diagram (50 % ellipsoid probability) of 2a 117
4.36 Packing diagram of 2a with hydrogen bonding interactions 117
4.37 ORTEP diagram (50 % ellipsoid probability) of 3a 120
4.38 ORTEP diagram (25 % ellipsoid probability) of the molecular structure of (4a) 122
4.39 Graphical illustration of the repetitive element of the 3D network formed by 4a 122
4.40 ORTEP diagram (50 % ellipsoid probability) of the molecular structure of 5a 124
4.41 Packing diagram of complex 5a 124
4.42 ORTEP diagram (50 % ellipsoid probability) of the molecular structure of 6a 125
4.43 Packing diagram of complex 6a 125
4.44 ORTEP diagram (50 % ellipsoid probability) of the molecular structure of 7a 131
4.45 ORTEP diagram (50 % ellipsoid probability) of the molecular structure of 8a 134
4.46 Packing diagram of 8a 134
4.47 ORTEP diagram (50 % ellipsoid probability) of the molecular structure of 9a 137
4.48 Packing diagram of complex 9a 137
4.49 ORTEP diagram (50 % ellipsoid probability) of the molecular structure of 10a 141
4.50 Packing diagram of complex 10a 141
4.51 The building units in 11a showing 50 % displacement ellipsoids. 144
4.52 ORTEP diagram (50 % ellipsoid probability) of the molecular structure of 1b 147
4.53 ORTEP diagram (25 % ellipsoid probability) of the molecular structure of 2b 151
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4.54 The molecular structure of 1c (50% displacement ellipsoids) 156
4.55 Fragment of a [001] hydrogen-bonded chain of 1c molecules 157
4.56 The molecular structure of 2c showing 50% displacement ellipsoids 159
4.57 Fragment of a [101] polymeric chain in the structure of 2c 159
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LIST OF SCHEMES
Scheme Title Page
1.1 The NᴖN-chelating diamines used in research work 15
2.1 Ligands used in research work for 1b and 2b 23
2.2 Ligands used in research work for 1c and 2c 25
3.1 Schematic sketch of synthetic procedure for complex 4a 43
3.2 Schematic sketch of synthetic procedure for complexes 3a and 5a 43
3.3 Schematic sketch of synthetic procedure for complexes 6a and 7a 44
3.4 Schematic sketch of synthetic procedure for complexes 8a, 9a and 10a 46
3.5 Schematic sketch of synthetic procedure for complexes (1b) and (2b) 48
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LIST OF ABBREVIATIONS AND SYMBOLS
Abbreviations Description
Δ change in
° degrees
°C degree centigrade
> greater than
< less than
λ max wavelength of maximum absorption
ѵ wavenumber cm-1 (FT-IR)
en ethylenediamine
phen 1, 10-phenanthroline
bipy 2,2'-bipyridine
salH2 salicylic acid
Hcinn cinnamic acid
cinn1- cinnamate
pABA1- 4-aminobenzoate
mABA1- 3-aminobenzoate
phtH2 phthalic acid
tphtH2 terephthalic acid
succH2 succinic acid
EtOH ethanol
MeOH methanol
NSAIDs non-steroidal anti-inflammatory drugs
% percent
1D one-dimensional
2D two-dimensional
3D three-dimensional
Å angstrom
aq aqueous phase
m.p. melting point
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cm-1 wavenumber (IR)
e. g. for example
FTIR Fourier Transform Infrared
i.e., that is
IR infrared
mmol millimole
pH -log10[H+]
UV-Vis Ultraviolet-Visible
XRD X-Ray Diffraction
DMSO Dimethyl sulfoxide
CSD Cambridge structural database
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CHAPTER 1
INTRODUCTION
1.1 Chemistry of Copper
Copper is a reddish colored, malleable, ductile and corrosion resistant metal. Copper, is the
29th element of the periodic table, and along with its heavier congeners-the other two coinage
metals i.e, silver (Ag) and gold (Au), it belongs to group 11 of the periodic table. The
electronic configuration of copper is [Ar] 3d10, 4s1 [1]. Although it has a relative abundance
of 68 ppm in the earth's crust, it is still the earth's 25th most abundant transition metal [2, 3].
Copper with its high electrical conductivity-which is second only to that of silver, is used in
making electrical wires [4]. Copper has three different oxidation states including, Cu1+, Cu2+,
and Cu3+. More commonly copper exists in +2 oxidation state. Copper(III) complexes are
mostly available in mixed-valent polynuclear copper complexes and have important role in
homogeneous catalysis [5].
The oxidation potential for Cu+/Cu+2 (Eo=-0.15) is less negative than that for the
Cu/Cu1+ (Eo= -0.52). Any oxidizing agent that can oxidize Cu/Cu+, can even more easily
convert Cu+ to Cu+2 , which justifies why Cu+2 is the most common oxidation state of copper.
The properties of copper in coordination chemistry are due to the almost noble metal
character, the intermediate stability, the reactivity of the d10 electron configuration in Cu(I),
and the relative small radius of the Cu(II) ion, which contributes to the high energy of
hydration and thus to the higher stability of Cu(II) (aq) over Cu(I) (aq) [6]. Cu (I) ions need
to be stabilized by chelating ligands.
Cu1+ has a d10 configuration and is associated with regular, cubic coordination
geometries. The preferred coordination geometries of such complexes are four-coordinated
tetrahedral or trigonal pyramidal structures, but three- and two- coordinate complexes have
also been reported. Furthermore, five-coordinated Cu(I) complexes are well known for
adopting either a square pyramidal or a trigonal bipyramidal geometry [7, 8].
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2
Table 1.1: Common oxidation states of copper with their coordination geometries
Oxidation
state
Coordination
Number Shape Examples
Cu(I), d10 2 Linear CuCl21-, CuBr21-
3 Planar K[Cu(CN)2], [Cu(SPMe3)3]ClO4
4 Tetrahedron [Cu(MeCN)4]+,CuI,[Cu(CN)4]-3
4 Distorted square
planar CuBr
5 Square pyramidal [CuBrCO]
CuII, d9 3 Trigonal planar Cu2(µ-Br)2Br2
4 Square planar CuO, [Cu(py)4]
5 Square pyramidal [Cu(pht)(phen)2]
6 Distorted
octahedron
[Cu(SO4)(C2H8N2)2]n,
K2[Cu(EDTA)]
6 Octahedron K2Pb[Cu(NO2)6]
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1.2 Chemistry of copper (II)
Copper(II) is the most common oxidation state of copper, as Cu(I) has a great tendency to be
oxidized to Cu(II), while Cu(II) shows little tendency for further oxidization to Cu(III). The
electronic configuration of copper (II) is [Ar] 3d94So. Cu2+ has a d9 configuration and in an
environment of cubic symmetry, can manifest Jahn-Teller distortions. Copper (II) complexes
possess a variety of coordination geometries and usually form tetrahedral, square planar,
square pyramidal, tetragonal and octahedral complexes.
1.2.1 General metabolic functions of copper
Copper is a biologically essential trace micronutrient and is found in all living organisms. Its
importance is also evident from the fact that, after iron and zinc, copper comes third in
abundance in the human body. Most of the copper is stored in liver, though its total amount
in the body is from 75 mg to 100 mg, it is found in every cell, especially in major organs like
brain, kidney, muscles and heart [9]. Copper also plays a pivotal role in our metabolism, as
many critical enzymes are copper dependent like oxidases and oxygenases [10].
Copper is required for the function of over 30 proteins It is acts as a cofactor and is
responsible for structural and catalytic properties of many metallo-enzymes. These enzymes
perform an array of biological processes. Some examples of cuproenzymes, together with
their biological role may include, cytochrome-c oxidase (electron transport, mitochondrial
oxidative phosphorylation, energy production and synthesis of phospholipids found in myelin
sheaths) [11], ceruloplasmin (feroxidase I) and feroxidase II (oxidation of Fe2+ to Fe3+,
transportation of Fe3+ to the red blood cells and blood formation), lysyl oxidase (synthesis of
collagen and elastin-which form connective tissue, and bone formation), tyrosinase (melanin
synthesis-pigmentation of hair, skin and eyes) [12], dopamine ß-hydroxylase (catecholamine
production, conversion of the neurotransmitter dopamine into norepinephrine) [13],
monoamine oxidase (oxidation of monoamines, metabolism of the neurotransmitters,
breakdown of the serotonin) [14], catechol oxidase (synthesis of melanin, conversion of
ortho-diphenols to the corresponding o-quinones accompanied by the reduction of oxygen to
water [15], copper/zinc superoxide dismutase (antioxidant), ceruloplasmin (anti-
inflammatory activity), iron metabolism, and copper transport in living organism [16, 17].
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1.3 Biological activities of copper (II) complexes
Copper (II) complexes have been found to be excellent SOD-mimetic agents. Copper/zinc
superoxide dismutase (Cu-Zn-SOD) is an antioxidant enzyme that contains an active site, in
which zinc (II) and copper (II) are bridged by deprotonated imidazole. It converts/ dismutates
superoxide ion into less harmful species i.e., H2O2 [18] in biological systems.
2O2−. + 2H+ → O2 + H2O2
This detoxification is proton assisted and is dependent on the ease of Cu(I)/Cu(II)
redox inter conversions [18]. Copper is also necessary for the synthesis of thyroxine, while
many Cu-containing proteins are involved in the electron transfer processes. Being a free
radical scavenger, copper acts as an antioxidant and prevents cell from damage [19].
Although, antioxidant enzymes like Cu-Zn-SOD, can be regarded as the organism’s
first line of antioxidant defense, their supplementation in treating such disorders, like
Alzheimer’s disease, and Parkinson’s disease however, is restricted. The reason is that
because of their high molecular weights, these cannot cross the cell membranes [20] and are
also rapidly degraded in biological systems [21]. A recent approach involves synthesis of low
molecular weight complexes that can mimic the enzyme activity. An important class of such
materials constitutes copper(II) complexes of N- and O-donor ligands. Many such copper(II)
complexes are considered as antimicrobial, antiviral, anti-inflammatory agents [22, 23].
These copper(II) complexes have also been found effective in the treatment of a
number of diseases including cancer and tumors due to their superoxide scavenging ability
[24, 25]. Low molecular weight copper complexes are important owing to their potential use
as catalysts in selective oxidation reactions [26]. Catalysis of oxygenation reaction in nature
occurs through metalloproteins having copper containing active sites [27].
Synthetic biomimetic copper complexes which can act as model systems for the study
of O2-activation chemistry are investigated [5, 28]. Such systems are synthetic analogues of
naturally occurring copper proteins like hemocyanin-a respiratory protein in arthropods and
mollusks that reversibly binds O2, and other enzymes [5].
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1.4 Metal carboxylate chemistry and their coordination modes
Metal carboxylates are extensively studied in various fields of chemistry including; inorganic
chemistry, coordination chemistry, bioinorganic chemistry, magnetochemistry, and
supramolecular chemistry. Being versatile ligands, they can assume different coordination
modes and can also have different nuclearities. Copper as a central metal atom, also has the
ability to coordinate with a great number of ligands to form coordinate complexes of varying
structural geometries, nuclearities and dimensions [29, 30].
The ubiquitous metal-carboxylate complexes are well known for their extensive
applications. From the coordination chemistry point of view, the bonding, structures, and
properties of metal carboxylates have inspired much interest of researchers. The coordination
between the carboxylate ligand and the metal can be classified into four different categories.
(i) Metal carboxylates having ionic nature
Ionic carboxylates have little cation-anion interaction [31, 32], as there are only coulombic
forces of attraction between positively charged metal ion and the negatively charged
carboxylates. The ionic carboxylates of all alkali metals, with the exception of lithium have
been reported, for example in sodium formate, the electrons are delocalised in the
carboxylate group and both C-O bonds are equal with the bond length of 1.27A [33].
(ii) Metal carboxylates with monodentate coordination mode
In lithium acetate (Li(CH3COO). 2H2O) the carboxylate moiety of acetate ion coordinates in
a monodentate fashion [34], as a result, one of the C-O bond distance involving the
carboxylate oxygen directly coordinated to lithium is longer (1.33 A) than the other O atom
which is doubly bonded to carboxylate carbon atom (1.22A).
(iii) Metal carboxylates with bidentate (chelating) coordination mode
In this mode, the carboxylate ion acts as a bidentate ligand, and coordinates to a metal centre
through its two carboxylate-O atoms, and forms a four-membered ring containing the metal
ion. This coordination can be either symmetrical bidentate chelating, having same C-O bond
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6
lengths or asymmetrical bidentate chelating, having different C-O bond lengths. An example
of such complexes is Zn(CH3COO)2. 2H2O [35].
(i) (ii) (iii) (iv)
Figure 1.1: Different coordination modes of metal carboxylates; (i) Ionic, (ii) monodentate, (iii) bidentate (sym), (iv) bidentate (asym)
(iv) Metal carboxylates with bridging coordination modes
The bridging modes can be classified into four basic types, depending on which electron
pairs (whether syn or anti), of carboxylate oxygens are used to coordinate with the metal
centre. These include syn-syn, syn-anti, anti-anti, and monodentate terminal bridging or
monoatomic bridging coordination modes (figure 1.3). The examples of each type include
Cu(O2CMe)2. 2H2O [36], Cu(O2CH)2 [37], Cu(O2CH)2. 4H2O [38], and
Hg(O2CMe)2(C6H11)3P) [39], respectively.
O
O
R
:
:
::
syn
anti
anti
Figure 1.2: Different lone pairs of metal carboxylates
The syn- electron pairs are more basic and geometry of the syn-syn bridge can bring
the metal centers close enough for magnetic interactions, which may lead to unusual
magnetic properties [40, 41]. The syn-syn mode is observed in dinulear complexes like
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7
copper(II) acetate dihydrate. In this Cu(II) carboxylate complex, the two copper centers are
connected through four syn-syn bridges, formed by four carboxylate groups, giving it a
paddle wheel or lantern shape. The anti-anti mode is observed in many carboxylate
complexes of ruthenium [42]. Monodentate terminal bridging (monoatomic bridging) mode
is quite rare and is actually an intermediate between other bridging modes. One such
complex is [Mn2(sal)4(H2O)4] [43].
A B C D
Figure 1.3: Various bridging modes in metal carboxylates: A= syn-syn, B= syn-anti,
C= anti-anti, D= monoatomic bridging
1.5 Structures and molecular geometries of copper (II)-carboxylate complexes
In the synthesis of copper(II) carboxylates, the copper(II) center acts as a lewis acid of
intermediate strength, which accepts electron pairs from caboxylate-O donor atoms. As
discussed above, these copper(II) caboxylate complexes may be tetra, penta, or hexa
coordinate and can possess versatile geometries and coordination modes. Their most
commonly encountered geometries are tetrahedral, square-planar, square-pyramidal, and
octahedral. Similarly, on the basis of nuclearity, these copper(II) carboxylates can be
classified as mononuclear, dinuclear to polynuclear.
1.5.1 Geometries of mononuclear copper(II) carboxylates
Mononuclear complexes can assume a variety of coordination geometries. The tetrahedral,
square planar, square pyramidal, trigonal bipyramidal, and octahedral geometries are
discussed as follows.
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8
1.5.1.1 Four-coordinate complexes:
Most of the copper(II) carboxylate complexes tend to assume geometries with higher
coordination numbers. This can be attributed to the oxophilicity of copper(II), due to which,
copper(II) exhibits the tendency to expand its coordination sphere and forms dimeric to
polymeric complexes [44]. Though tetrahedrally coordinated, homoleptic copper(II)
carboxylates are not known. However, the ternary copper(II) carboxylate complexes having
tetrahedral geometry have been reported.
A B
Figure 1.4: Four-coordinate copper(II) complexes; A= with distorted tetrahedral geometry
[Cu(neocuproine)(salH)2], B= having square planar geometry [Cu(O2CMe)2(bipy)]
One example of a tetrahedral complex is [Cu(neocuproine)(salH)2], which is a
copper(II) complex of neocuproine (2,9-dimethyl-1,10-phenanthroline), and salicylic acid.
The complex has two asymmetric units. Each Cu(II) ion is four-coordinated by two N atoms
from chelating neocuproine, and two O atoms from two salicylate (salH1-) anions. The
CuO2N2 unit adopts a distorted tetrahedral geometry (figure 1.4A) [45]. The example of
square planar complex is [Cu(O2CMe)2(bipy)](figure 1.4B) [46].
Out of the two tetra-coordinate geometries, square planar geometry is more stable
than the tetrahedral one and hence, is more frequently encountered [45-48]. The reason for
the non expansion of coordination number may be attributed to the stability of the square
planar geometry due to the steric interactions of the attached ligands, which prevent other
incoming groups from approaching closer to the central metal ion. All these complexes show
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9
π-π stacking interactions between aromatic rings, and an extensive O-H…O and N-H…O
hydrogen-bonding network, which stabilize crystal lattice.
1.5.1.2 Five-coordinate copper(II) complexes
Both square pyramidal and trigonal bipyramidal geometries most frequently occur in five-
coordinate copper(II) complexes. EPR studies of penta-coordinated Cu(II) complexes have
shown that these two geometries are interconvertible. This change is temperature-dependent
and involves shifting of the unpaired d electron on copper(II) ion from the dz2 (in trigonal
bipyramidal geometry) to the dx2-y2 orbital (in square pyramidal geometry) [49].
A B
Figure 1.5: Copper(II) complexes with square pyramidal geometry; A =
[Cu(neocuproine)(5-chloro-2-hydroxybenzoate)2], B= [CuCl(neocuproine)(benzoate)]
Ternary mononuclear copper(II) complexes of neocuproine (2,9-dimethyl-1,10-
phenanthroline) with 5-chloro-2-hydroxybenzoate (figure 1.5A) [50], benzoate (figure 1.5B)
[51], 2-hydroxybenzoate [45] and 4-hydroxybenzoate [52] can be quoted as examples in
which the coordination environment around the central copper atom is square pyramidal.
Trigonal bipyramidal geometry is exemplified in (figure 1.7 C) [53] in dimeric complexes.
1.5.1.3 Six-coordinate copper(II) complexes
Hexa-coordinate copper(II) complexes assume octahedral coordination geometry. A number
of mononuclear copper(II) carboxylate complexes are known to possess octahedral
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10
coordination geometry. In the complex [Cu(C7H6N2)2(C7H5O3)2], (where C7H6N2
=benzimidazole, C7H5O3 = 4-hydroxy-benzoate anion), the CuN2O4 chromophore assumes
distorted octahedral geometry by two benzimidazole ligands and two chelating 4-
hydroxy-benzoate anions. Neighboring benzimidazole groups are also interlinked through
π-π stacking interations [54].
A B
Figure 1.6: Copper(II) complexes with octahedral geometry around copper(II) ion.
A = [Cu(ndmen)2(salH)2].H2O, B = [Cu(C12H8N2)(C9H9O4)2]
The X-ray crystal structure of [Cu(salH)2(ndmen)2].·H2O (where ndmen=N,N-
dimethylethylenediamine) (figure 1.6 A) shows that the CuN4O2 chromophore in the complex
is coordinated by two chelating ndmen ligands in trans disposition and two monodentate
salicylate ions leading to distorted trans-octahedral geometry [55]. The monomeric complex
[Cu(C12H8N2)(C9H9O4)2] (where C12H8N2 = 1,10-phenanthroline, C9H9O41- = 3,4-
dimethoxybenzoate1-) also has octahedral geometry (figure 1.6 B) [56].
1.5.2 Bi-nuclear copper(II) carboxylate complexes
Dimeric copper(II) carboxylate derivatives are frequently encountered among copper(II)
complexes. Depending on whether syn or anti electron pairs are involved in coordination,
bridging carboxylates can assume syn-syn, syn-anti, or anti-anti orientations.
Many dinuclear copper(II) carboxylates possess the classical paddlewheel (lantern)
type structure. This familiar motif is present in [Cu(salH)4(EtOH)(H2O)] (figure 1.7 A), in
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11
which the two copper centers are linked by four carboxylato oxygens from four salH1- anions
in a syn-syn fashion, while apical positions are occupied by ethanol (EtOH) and water
molecules [57].
In dimeric complex [Cu2(bipy)2(salH)(sal)]. ClO4, the cationic moiety
[Cu2(bipy)2(salH)(sal)]1+ has two copper(II) centers, each Cu(II) is coordinated by a
chelating 2,2ʹ-bipyridine and by a monodentate carboxylate-O atom and phenolate-O atom of
salicylate ion. This complex is of interest because, one salicylate ligand, still has its
carboxylic H-atom in an undissociated form [58].
A B C
Figure 1.7: X-ray structures of binuclear copper(II) carboxylates; A= [Cu(salH)4(EtOH)(H2O)], B= [Cu2(bipy)2(OAc)3], C= [{Cu(phen)2}2(μ-CH3COO)][PF6]3
The structure of dinuclear copper(II) complex, [{Cu(phen)2}2(μ-CH3COO)][PF6]3, is
interesting as two independent Cu(II) centers show two different geometries with a trigonal
bipyramidal geometry for the Cu1 center and a distorted square-based pyramidal geometry
for the Cu2 center, each copper center is bridged by an acetate anion and shows a syn–anti
coordination mode (figure 1.7 C) [53].
Another complex [Cu2(bipy)2(OAc)3], is dimeric, consisting of two copper(II)
centres, each coordinated by a cheating bipy, and bridged by three acetate1- anions, two in
bridging chelating mode and the third OAc1- in the rare mono-atomic bridging mode (figure
1.7 B) [59]. The crystal structure of dimeric complex [Cu(Neo)(sal)]2 shows that the
coordination geometry of Cu(II) ions is a distorted square pyramid [50].
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1.5.3 Trinuclear copper(II) carboxylate complexes
Valigura et al (2004) reported a trinuclear complex [Cu3(dns)2(Hdns)2(H2O)4]. 4H2O (where
dnsH2 = 3,5-dinitrosalicylic acid). In this centrosymmetric complex, Cu1 centre is square
planar, whereas the outer Cu2 and Cu3 centres exhibit square pyramidal geometries. Each
outer copper(II) is coordinated by a phenoxy-O and a carboxylate-O from dnsH1- ligands,
while the inner Cu(II) is coordinated by two bridging chelating dns2- groups and hence is
connected to both outer Cu(II) ions (figure 1.8) [60].
Figure 1.8: X-ray structure of trinuclear complex [Cu3(dns)2(dnsH)2(H2O)4].4H2O
1.5.4 Polynuclear copper(II) complexes
Copper(II) carboxylates with more than three copper(II) centers are also frequent. A
hexanuclear complex [Cu6(tmen)6(µ-N3)2(µ-C2O4)3(H2O)2][ClO4]4. 2H2O (where tmen =
Me2NCH2CH2NMe2, N31-= azido1- , C2O42- = oxalate2-) [61] has been reported. Adducts of
copper(II) benzimidazole with malonate2- (figure 1.9 A) and salicylate1- (figure 1.9 B) anions
lead to two polynuclear complexes including catena-((μ2-malonato)-aqua-(1H-
benzimidazole)copper(II)) [62], and Catena-((μ2-salicylato)-bis(1H-benzimidazole)-
(salicylato)-copper(II)) [63], respectively.
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13
A B C
Figure 1.9: X-ray structures of polymeric copper(II) carboxyates; A = catena-((μ2-
malonato)-aqua-(1H-benzimidazole) copper(II)), B = Catena-((μ2-salicylato)-bis(1H-
benzimidazole)-(salicylato)-copper(II)), C = [Cu(ipt)(dap)H2O]n. nH2O
The complex [Cu(ipt)(dap)H2O]n. nH2O (where ipt2- = 1,3-benzenedicarboxylate
dianion, dap = 1,3-diaminopropane) shows a distorted square pyramidal structure in which
two O atoms, one each from bridging ipt2- units, and the two N atoms of the chelating bonded
dap ligand form the basal square plane, while the aqua-O atom occupies axial position (figure
1.9 C) [64].
1.6 Supra-molecular architechtures based on copper(II) carboxylates
The design and construction of metal-organic frameworks is important in the fields of supra-
molecular chemistry and crystal engineering. Both covalent and non covalent interactions
play an important role in the self-assembly of supramolecules and in molecular recognition.
Non-covalent interactions (also called van der Waals interactions) can be categorized in to
following main types including; halogen-halogen and C-H…X interactions (where X= O, N,
F, Cl or Br etc.), hydrogen bonding interactions for example of O-H…O, N-H…O type, and
π···π interactions especially among aromatic systems.
Among these, hydrogen bonding and π···π interactions play a crucial role in
establishing structure-activity relationship in various biological processes [65, 66]. Cation…π
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14
interactions play an important role in the selectivity process of potassium channels, while
anion…π type interactions are under study for their potential applications as anion receptors
in molecular recognition [67-70].
The metal-organic frameworks with 1-D, 2-D, and 3-D spatial arrangements can be
designed with organic molecules having hydroxyl, floro, amino and carboxylate functional
groups.
In our research work, some of the synthesized mixed ligand copper(II) carboxylates
contain hydroxyl, chloro and amino groups in addition to carboxylate group as a major
functionality. In almost all complexes, the carboxylate moiety is in deprotonated form and
because of the absence of carboxylate-H atom, the COO1- moiety can only form hydrogen
bonds with aqua-H atoms of either coordinated and/or lattice water molecules which serve to
keep the complex molecules together via extensive H-bonding.
1.7 The diamine ligands
In order to synthesize metallopharmaceuticals which have less toxicity, more selectivity
and and can bind through non covalent interactions, the diamine adducts of copper(II)
carboxylates were selected. In this respect both open chain diamines like N,N,N′,N′-
tetramethylethylenediamine and ethylenediamine as well as NᴖN heterocyclic diamines like
bipyridine, and 1,10-phenanthroline have been used in our work. These diamines-׳2,2
although exhibit invariably bidentate (chelating) coordination mode, but their synthesized
ternay complexes with carboxylate ligands manifest great structural diversity and showed a
variety of coordination modes and geometries. Most of these diamines have been reported to
possess antimicrobial effects.
Onawumi O. O. E.et al (2013) reported two complexes, [Cu(en)(phen)2]·2Br1-.
2Phen.·8H2O and [Cu(en)(phen)2]ClO4, having [Cu(en)(phen)2]2+ cation with antimicrobial
activities similar to the known standard drugs including amplicilline, chloramphenicol,
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15
ciprofloxacin and norfloxacin [71]. Both 1,10–phenanthroline and 2,2ʹ–bipyridine are
bidentate chelating ligands that form very stable complexes with copper(II) ion.
NNCH3
CH3
CH3
CH3 NH2NH2
N,N,N′,N′-tetramethylethylenediamine ethylenediamine
N N N N
bipyridine 1,10-phenanthroline-׳2,2
Scheme 1.1: The NᴖN-chelating diamines used in research work
Agwara, M.O. et al (2010) studied antimicrobial activities of the complex
[Cu(bipy)(phen)(H2O)2]Cl2 .2H2O together with cobalt (II) and Zinc (II) mixed-ligand
complexes containing 1,10-phenanthroline and 2,2ʹ–bipyridine. This complex was found to
be biologically active [72].
Prasad, R. et al (2002), synthesized two mixed ligand copper(II) complexes
[Cu(dien)(phen)](ClO4)2 and [Cu(dien)(bipy)](BF4)2 and tested their antimicrobial activity. It
was found that antimicrobial activity of the copper(II)-bipy complex was higher than the
coordinated copper(II)-phen complex [73]. Puglisi, A., et al (2003), have studied the
application of pure phenanthroline or bipyridine containing macrocycles in asymmetric
catalysis [74].
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16
1.8 Aims and Objectives
The main goal of this study is to understand the coordination environment and
molecular geometry of ternary copper(II) complexes of diamines and carboxylates.
To attain this goal the present study was carried out with the following objectives
a. Synthesis of copper(II) complexes with carboxylates incorporating diamines
b. Characterization of the complexes by elemental analysis (CHNS), Uv-visible and
FTIR, spectroscopic methods
c Characterization of the complexes by thermal (TGA/DTG) analyses
d Structural characterization of the synthesized complexes by single crystal X-ray
diffraction analysis
e To study the biological activity of some of the complexes
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17
CHAPTER 2
LITERATURE REVIEW
Ternary metal-based carboxylates incorporating diamines as ligands are important for their
biological significance as well as for their formative role in the design and synthesis of
metal-organic hybrids. A brief literature survey regarding the properties of various ligands
utilized in the research work and their complexes that have been reported, is presented as
follows.
Benzoic acid has been utilized as a food preservative, and due to its antifungal
properties, it is an important constituent of ointments like Whitfields, and bensal for the
treatment of fungal infections of skin [75]. Similarly, p-aminobenzoic acid (pABAH), also
known as vitamin B10 or factor R is a naturally occurring substance that acts as a precursor
in biosynthesis of folic acid by bacteria, plants, and fungi. P-aminobenzoic acid has been
used as a protective drug against solar insolation, as a part of sun-screen lotions and in
diagnostic tests for the state of the gastrointestinal tract in medicine. It is an antioxidant, an
interferon inducer and immuno-modulator and has antithrombotic, fibrinolytic, antiherpetic
effects. "Actipol" is a drug that contains p-aminobenzoic acid [76-83].
Succinate acts as a bis-bidentate bridging ligand. The carboxylate moieties of each
succinate coordinate with their respective copper(II) centers in a bidentate manner. Hence,
each succinate acts as a tetradentate ligand [84]. Another complex with bis-bidentate
coordination of succinate2- is [Cu2(succ)(bipy)4](NO3)2. 10.5H2O [85], while the complex
[Cu2(succ)(bipy)4]. (succ). 12H2O has succinate2- anion linked to copper(II) ions in a bis-
monodentate mode [86]. Since most of the reported complexes are dimeric to polymeric,
some examples of these complexes are discussed here. The complex
[(phen)2Cu(succ)Cu(phen)2]succ. 12.5H2O (succ2- = doubly deprotonated anion of succinic
acid) represents a dimeric complex [84]. 1D chain forming complexes are exemplified by
[Cu2(μ-OH2)2(succ)(bipy)2(NO3)2]n and [Cu2(μ-OH2)2(succ)(phen)2(NO3)2]n [87].
The complex [Mn(H2O)2(bipy)(succ)]. H2O forms a polymeric 1D helical chain [88],
while a 2-D grid is formed by the complex {[Cu4(succ)2(bipy)4(H2O)2](ClO4)4(H2O)}n [87].
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18
A discrete octanuclear complex [Cu8(succ)4(phen)12]. (BF4)8. 8H2O [87], and a polymeric
hexanuclear complex [Cu6(phen)6(succ)4]. 2NO3. 5O [89] is also reported.
Ternary copper(II) phthalate complex [Cu(pht)(phen)2] has been investigated for its
pharmacological potential, owing to its DNA binding properties. It also acts as a chemical
nuclease with high antitumour activity. The complex [Cu(pht)(phen)2] is mononuclear and
contains the pht2- dianion bound to the metal through one of its carboxylate groups in a
monodentate coordination mode.
Another monomeric complex is [Cu(phtH)2(1-CH3Im)2], in which phtH1- anion is
present [91]. The [Cu2(phen)2(phtH)2(NO3)(H2O)]1+ cationic moiety present inthe dinuclear
complex [Cu2(phen)2(phtH)2(NO3)(H2O)]. NO3. 2H2O, contains two Hpht1-ions. Each Hpht1-
has one singly deprotonated carboxylate group and an undissociated carboxylic acid group.
The later does not take part in coordination. The two O atoms of each deprotonated
carboxylate moiety form syn–syn carboxylato bridges which coordinate with the two
copper(II) centers [92].
Mefenamic acid (mefH = 2-(2,3-dimethylphenyl)aminobenzoic acid) is a derivative
of N-phenylanthranilic acid. It is a widely used non-steroidal anti-inflammatory drug
(NSAID) that is chemically similar to other tolfenamates such as tolfenamic and flufenamic
acids. Like other NSAIDs, it is a potent analgesic, anti-inflammatory and antipyretic agent,
and its use is prevalent for the treatment of diseases like osteoarthritis, and nonarticular
rheumatism [93-94]. Similarly, in the polymeric square pyramidal complexes
{[Cu(pht)(Phen)(H2O)].·H2O}n [95], and [Cu(pht)(H2O)(phen)]. 0.5H2O [96], pht2- anion
bridges two adjacent Cu2+ ions with its two oxygen atoms from two carboxylato moieties to
form one-dimensional chains.
A small description of some of the reported copper(II) complexes of tmen is given
now. Estes, E.D. (1975) et al have reported crystal structure of the distorted square pyramidal
complex [Cu(tmen)Cl2]2. The structure is similar to its bromo analogue [97].
Geetha K, and coworkers (1996), have described synthesis, and single crystal
analyses of two ferromagnetically coupled dinuclear cationic complexes of the type [Cu2(μ-
OR)(μ-O2CPh)2(tmen)2]+ (R = H, Me) (figure 2.1 A). The ferromagnetic character is
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19
attributed to the pyramidal geometry at the oxygen of the hydroxo/methoxo bridging ligand.
The coordination environment around Cu1 and Cu2 centres is square pyramidal [98].
A B
Figure 2.1: Copper(II) complexes of tmen with monocarboxylates;
A= [Cu2(μ-OH)(μ-O2CPh)2(tmen)2]+, B= [Cu(tmen)(BA)2].pyridine
J. Chris Slootweg et al (2008) have reported a complex [Cu(tmen)(acetate)2], the
Cu(II) ion is coordinated by two N atoms from the chelating tmen and two O atoms from two
acetate anions forming a distorted square-planar coordination environment. In addition, there
are longer contacts between Cu and the second O atom of each acetate ligand [Cu—O =
2.509 (2), 2.531 (2) Å], due to which an alternative description can be a distorted octahedron
[99].
L. Parkanyi et al (1995) have described synthesis, and crystal structure of a complex
[Cu(tmen)(BA)2].pyridine (figure 2.1 B). The coordination geometry around the copper(II)
centre of the centrosymmetric mononuclear complex is distorted square planar, by two
monodentate benzoate-O atoms and two N atoms of chelating tmen, while pyridine is present
as an outer sphere ligand [100].
J. Ferjani et al (2005) have reported an octahedral polymeric complex
{[Cu(C2O4)(tmen)] 4H2O}n (figure 2.2 A), in which each Cu(II) centre is coordinated by two
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20
N atoms of bidentate tmen and by four O atoms of two bridging oxalate dianions forming
infnite chains. The structure is supported by hydrogen-bonding leading to a three-
dimensional network [101].
A B
Figure 2.2: Copper(II) complexes of tmen with dicarboxylates; A =
{[Cu(C2O4)(tmen)]4H2O}n, B= [Cu2(pht)(tmen)2(H2O)2]
A. Taha et al (2014), have synthesized a new dimeric ternary copper(II) complex
[Cu2(pht)(tmen)2(H2O)2(NO3)2] H2O (figure 2.2 B) complex and characterized it by spectral,
magnetic, molar conductivity and TGA analyses [102].
H. Muhonen et al (1978), have prepared the complex [Cu(tmen)(salicylate)2] (figure
2.3 A). The Cu(II) centre in the CuN2O4 chromophore is coordinated by four carboxylate-O
atoms from two chelating salicylate ligands and two N atoms of bidentately coordinated
tmen, resulting in a distorted octahedral geometry [103].
A. Saini and coworkers (2015), have reported two mononuclear ternary copper(II)
complexes of tmen including [Cu(tmen)(4-chloro-2-nitrobenzoate)2] (figure 2.3 B) and
[Cu(tmen)(5-chloro-2-nitrobenzoate)2] (figure 2.3 C). Characterization is done through
elemental analyses, spectroscopic techniques (UV–Vis, FT-IR, EPR), TGA analysis,
magnetic moment determination, and single crystal analyses. Both the complexes are
monomeric with distorted square planar coordination geometry around Cu(II) centers in a
CuN2O2 chromophore, defined by two N atoms from a chelating tmen and two carboxylate-O
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21
atoms. The two structures are stabilized by various non covalent interactions, leading to a 3-
dimensional framework [104].
A B C
Figure 2.3: Copper(II) complexes of tmen with carboxylates A =
[Cu(tmen)(salicylate)2], B = [Cu(tmen)(4-chloro-2-nitrobenzoate)2] and C =
[Cu(tmen)(5-chloro-2-nitrobenzoate)2]
Copper is a biologically essential trace mineral for all living things including
microorganisms, animals and plants. In biological systems, it acts as a catalytic cofactor for
numerous metallo-enzymes (tyrosinase, cytochrome C oxidase, ceruloplasmin, dopamine
hydroxylase, etc.) and hence, controls many metabolic pathways for example, mitochondrial
oxidative phosphorylation, iron metabolism, transport of O2, cell growth, detoxification of
ROS (reactive free radical species) etc. The characteristic feature that enables copper to
manifest biological properties, is its ability to undergo copper(I)-copper(II) redox
interconversions in many metallo-enzymes like catechol oxidase [105], dopamine
monoxygenase [106], methane monoxygenase [107], and tyrosinase [108]. One important
copper containing metalloenzyme is Cu-Zn superoxide dismutase (Cu-Zn SOD) that is a
natural antioxidant and dismutates reactive and toxic superoxide O2- into less toxic hydrogen
peroxide (H2O2) and O2 [109].
Complexation of biologically active compounds like carboxylates, and NᴖN
heterocyclic chelators with the metals which themselves possess biological properties, may
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22
lead to pharmacologically important ternary complexes. One such ligand, p-aminobenzoic
acid, is an important intermediate in the synthesis of folic acid, which is a constituent of the
vitamin B complex. It is a growth factor in plants, in certain micro-organisms with especially
Enterococci and Lactobacilli, and in animal and plant tissues [110-111].
Besides its applications as a good growth factor for many microbes, p-aminobenzoic
acid, also known as vitamin H, is well known for its potent natural antimutagenic activity
[38]. Cinnamic acid and its derivatives are dietary phenolic compounds that occur naturally
in fruits, vegetables, and flowers are well reputed for their biological properties. Their
antioxidant [113-114], antimicrobial [115-116], anti-inflammatory [117], cytotoxic [118],
anticancer [119], antitumor [120-122], antiviral [123], antifungal [124] activities have been
reported.
There is an increasing surge to design and synthesize ternary copper(II) complexes
incorporating bio-ligands like carboxylic acids, with NᴖN-heterocyclic ligands like
phenanthrolines and bipyridines, as most of them are good antioxidants and possess anti-
infective, antifungal, and antibacterial activities [125-127]. The other biological properties of
these copper-based metallo-drugs include their biomimetic action like Cu-Zn SOD enzyme,
and their DNA binding ability, leading to their applications as chemical nucleases, DNA
probes, and chemo-preventive, anticancer, antitumor agents [128-133].
Another reason for the selection of copper(II) ion for complex formation is its
peculiarity to display a variety of coordination shapes. Similarly, in addition to the biological
activity, multifunctional aromatic carboxylates such as phthalic acid, terephthalic acids, o-,
m-, and p-aminobenzoic acids provide more than one potential binding sites around the
aromatic ring. Ternary copper(II) carboxylates have been reported to exhibit rich structural
diversity in their coordination modes, molecular geometries, and their various nuclearities.
The study of diversity in coordination modes of carboxylate moiety is especially important
for the synthesis of metal-organic frameworks (MOFs).
Many ternary copper(II) carboxylates with Nᴖ
N-heterocyclic ligands such as
bipyridines have been reported which exhibit a variety in coordination geometries. These
complexes contain carboxylate moieties that assume versatile coordination motifs, leading to
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23
complexes with different nuclearities including mononuclear [134], binuclear [135-137],
trinuclear [138], or tetranuclear [139-140], hexanuclear [141] and polynuclear [142]
complexes.
The various coordination modes adopted by carboxylate moiety in mixed ligand
copper (II)-carboxylates of 2,2′-bipyridine (C10H8N2) include monodentate, bidentate
(chelating), and bridging modes. In the mononuclear complexes [Cu(C8H5O3)2(C10H8N2)]
and [Cu(C7H4IO2)2(C10H8N2)(H2O)], 4-formylbenzoate and (C8H5O31-) 4-iodobenzoate
anions (C7H4IO21-) coordinate to Cu(II) ion in a monodentate manner [143-144].
NH2
O
OH
O
OH
N
N
P-aminobenzoic acid, 2,2′-bipyridine cinnamic acid
Scheme 2.1: Ligands used in research work for 1b and 2b
The complexes [Cu(C4H4O4)(C10H8N2)(H2O)]. 2H2O and [Cu(C8H7O3)2(C10H8N2)].
H2O can be quoted as examples of bidentate chelating mode, in which 2-methylmalonate
(C4H4O42-) [145], and 3-methoxybenzoate (C8H7O31-) [148] anions assume bidentate or
chelating modes. Bridging coordination mode is more frequent in carboxylic acids having
more than one carboxylate moieties. The different modes of coordination of carboxylate
oxygen atoms to Cu(II) may include any of the syn-syn, syn-anti and anti-anti configurations.
This fact further increases the structural versatility of copper(II) carboxylates. In some
interesting complexes, more than one such configuration is reported [147-148].
Introduction of a chelating 2,2′-bipyridine into a copper(II)-carboxylate with paddle
wheel structure like [Cu2(O2CCH3)4. 2H2O] involves serious structural perturbations that
might lead to a polymer such as [-Cu2(O2CCH3)2(2,2′-bipy)2-O2CCH3-Cu2(O2CCH3)4-
O2CCH3-]n that consists of 1-D polymeric chains, containing alternate Cu2(O2CCH3)4 and
[Cu2(O2CCH3)2(2,2′-bipy)2]2+ units, interlinked by bridging acetato oxygen atoms in syn-anti
mode. The Cu2(O2CCH3)4 unit has four chelating bridging acetates connecting the two
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24
copper(II) centres in syn-syn configuration, and two axial ones exhibiting syn-anti mode. The
cationic unit [Cu2(O2CCH3)2(2,2′-bipy)2]2+ however has two acetate groups in monoatomic
bridging mode which is quite rare [147]. The complex [Cu2(O2CCH3)4(2,2′-bipy)2]. 2H2O can
be quoted as another example of a complex possessing the dimeric structure with acetate
(O2CCH3)1- anions connecting the two Cu(II) centers in a bridging chelating fashion but
possess syn-anti configuration [147]. Similarly, the anti-anti configuration of malonate (mal)
in complex {[Cu(bipy)(H2O)][Cu(bipy)(mal)(H2O)]}(ClO4)2 leads to antiferromagnetic
coupling interactions through OCCCO bonds of malonate [74]. [Cu(O2CCH3)2(2,2′-bipy)],
on the other hand is the complex in which the paddle wheel arrangement is completely lost
and a monomer is obtained [149].
Self-assembly of the these monomeric and dimeric units leads to multi-dimensional
supramolecular networks, interwoven by non-covalent interactions like π-π stacking, and
hydrogen bonding interactions [143-148].
Copper containing enzymes perform many functions and take part in a large number
of biochemical processes such as growth, cell differentiation, mitochondrial oxidative
phosphorylation, catecholamine production, antioxidant protection, anti-inflammatory
activity iron metabolism etc [150-160].
A B C
Figure 2.4: Structures of ternary copper(II)-bipy-carboxylates; A=
[Cu(bipy)(BA)2(H2O)], B= [Cu(bipy)(pABAH)(pABA)]2. (NO3)2. (H2O)3/2, C=
[Cu(bipy)(ClBA)2]2
Literature is replete with the copper(II) complexes of 1,10-phenanthroline and
carboxylic acids that are known to exhibit a wide range of pharmacological applications due
to their antiviral [161], antimicrobial [162-164], anti-mycobacterial [165-166], anti-
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25
inflammatory, and anti-candida [167], antitumor and anti-mutagenic activities [165-173].
Their relatively low molecular weights make their use attractive as drugs [168].
O
OH
N
N
NH2
O
OH
Scheme 2.2: Ligands used in research work for 1c and 2c
There has been an increasing surge in research related to the synthesis and study of
copper(II) complexes of 2,2′-bipyridine or 1,10-phenanthroline and carboxylates [169-170,
172-190]. These complexes exhibit structural diversity, and form mononuclear, binuclear, or
even polynuclear supramolecular complexes. Although 1,10-phenanthroline is almost
invariably chelating, meta aminobenzoate is a multifunctional ligand, with two potential sites
of attachment with the copper(II) ion, one through its amino group and other through its
carboxylate group.
A B C
Figure 2.5: Copper(II) complexes of phen with benzoate and 2-fluorobenzoate A=
[Cu(phen)(C9H9O4)2], B= [Cu(phen)2(C7H5O2)]. 2(C7H6O2). Cl1-, C= [Cu(phen)(C7H5O2F)2]
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26
Due to their variable ligation, carboxylate ions might involve; monodentate [169,
172-183] bidentate (chelating), including both symmetrical and asymmetrical, and chelating
bridging coordination modes [170, 183-189]. Dicarboxylates usually form binuclear, or
polymeric complexes exhibiting bis-monodentate or chelating bridging modes [170, 172-173,
, 189]. Weak interactions like hydrogen bonding of different types like O-H…O, O-H…N,
C-H…O etc, and π–π stacking interactions between different phenantroline moieties and with
aromatic carboxylates, play a very important role in the formation of supramolecular
architectures [169, 172, 173, 178, 181]. The unique ability of copper to manifest biological
copper(I)—copper(II) redox interconversions makes it an attractive candidate for its function
as a catalytic cofactor. Figure 4.1 shows monodentae (figure 4.1 B, and C), and bidentate
(figure 4.1 A) [150] coordination modes of carboxylate moieties.
A considerable number of copper(II) complexes of 1,10-phenanthroline and
monocarboxylic acids (acetic, benzoic, 2-fluorobenzoic, formic, lactic, and propionic) have
been reported [170, 179, 184, 185, 188, 190]. Except acetate and propionate complexes, the
carboxylate ligand in these complexes coordinates in a monodentate terminal mode. The
acetate and propionate ions behave as bridging ligands [170, 179].
In conclusion, the literature is replete with mixed ligand copper(II) complexes of
diamines incorporating carboxylates. These complexes exhibit a great structural variety and a
wide range of applications in various fields of science.
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27
CHAPTER 3
EXPERIMENTAL
3.1 Materials and methods
CuCl2.2H2O,1,10-phenanthroline and 2,2′-bipyridine were purchased from Merck chemical
company Germany, while N,N,N′,N′-tetramethylethylenediamine, benzoic acid, cinnamic
acid, acetylsalicylic acid, phthalic acid, o-chlorobenzoic acid, mefenamic acid, p-amino
benzoic acid, terephthalic acid succinic acid, tartaric acid, salicylic acid, methanol and NaOH
were purchased from Sigma-Aldrich, chemical company, and are used in the same condition
as received. Distilled water used was singly distilled. The melting points were obtained in a
capillary tube using a Gallenkamp, serial number C040281, U.K, electro–thermal melting
point apparatus. Elemental analyses for C, H and N were carried out using a Perkin–Elmer
2400 II elemental analyzer. TGA was performed on TGA instrument Q500, USA, in N2
atmosphere at the rate 10 ºC per minute. A few samples were done in static air , and it is
mentioned in their figures. Infrared absorption spectra were recorded as KBr pellets with
Avatar 360 E.S.P. Nicolet FT/IR spectrometer in the range of 4000–400 cm-1. Uv-visible
spectra in DMSO were taken using Mega-2100 Double Beam Uv-Visible spectrophotometer.
3.2 Single crystal X–ray structure determination of complexes
Since the reaction products were good quality crystals, so single crystal analysis was carried
out for all the complexes including 1a-11a, 1b-2b, 1c-2c.
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28
3.2.1 Single crystal X–ray structure determination of complexes 1a-11a
The X-ray data forcomplexes 1a-11a are collected on Bruker SMART APEX-II CCD
diffractometer at 296 K, by using graphite monochromated MoKα radiation (λ = 0.71073 Å).
Data were collected and reduced by SAINT software [177]; data reduction: SAINT;
program(s) used to solve structure: SHELXS-97 (Sheldrick, 2008); program(s) used to refine
structure: SHELXL-97 (Sheldrick, 2008); [178] molecular graphics: ORTEP-3 for Windows
(Farrugia, 2012) and PLATON (Spek, 2009); software used to prepare material for
publication: WinGX (Farrugia, 2012) and PLATON [179-180]. The positions of oxygen
bonded hydrogen atoms were taken from difference Fourier maps and these hydrogen atoms
were refined isotropically with accompanying DFIX/DANG commands. Details concerning
data collection and analysis are reported in tables 3.1-3.6.
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29
Table 3.1: Structure refinement parameters of complexes 1a-2a
1a 2a
Formula C20H30CuN2O6 C20H28CuN2O7
Formula Weight(g mol1-) 458.00 471.98
Temperature (K) 296(2) 296(2)
Wavelength (Å) 0.71073 0.71073
Radiation type MoKα MoKα
Crystal system Monoclinic Orthorhombic
Space Group C 2/c P b c a
a (Å) 22.8512(10) 16.8070(7)
b (Å) 8.4249(3) 11.6652(6)
c (Å) 11.6074(5) 22.8878(12)
α (deg) 90 90
β (deg) 95.659 (2) 90
γ (deg) 90 90
V (Å3) 2223.75(16) 4487.3(4)
Z 4 8
ρcalc (g cm–3) 1.368 1.397
F(000) 964 1976
µ (mm–1) 1.299 1.015
Limiting indices; h, k, l −27 ≤h≤ 26 -21≤h≤12
−9≤k≤9 -14≤k≤14
−9≤l≤13 -29≤l≤-27
Reflections: collected. 7819 20729
Reflectionsuniq 1941 4875
Data/restraints/parameters 1941 /11/ 152 4875/6/284
R1, wR2 0.0305, 0.0805 0.0424, 0.1058
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30
Table 3.2: Structure refinement parameters of complexes 3a-4a
3a 4a
Formula C36H42CuN2O4 C41H60Cu2N8O9
Formula Weight(g mol1-) 658.29 936.05
Temperature (K) 296(2) 293(2)
Wavelength (Å) 0.71073 0.71073
Radiation type MoKα MoKα
Crystal system monoclinic Monoclinic
Space Group C 2/c C 2/c
a (Å) 8.5257(9) 22.4722(18)
b (Å) 13.3557(15) 7.5639(6)
c (Å) 30.039(3) 16.5090(15)
α (deg) 90 90
β (deg) 91.644(6) 124.950(3)
γ (deg) 90 90
V (Å3) 3419.0(6) 2300.1(3)
Z 4 2
ρcalc (g cm–3) 1.224 1.352
F(000) 1388 984
µ (mm–1) 0.682 0.984
θ range () 2.835 -27.000 2.211-24.997
Limiting indices; h, k, l -10≤h≤10 -26≤h≤26
-16≤k≤13 -6≤k≤8
-38≤l≤38 -19≤l≤19
Reflections: collected. 13285 1988
Reflections uniq 3648 1881
Data/restraints/parameters 3648/0/207 1988/6/157
R1, wR2 0.0779, 0.1876 0.0370, 0.1037
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31
Table 3.3: Structure refinement parameters of complexes 5a-6a
5a 6a
Formula C20H24Cl2CuN2O4 C24H31.39CuN2O4.70
Formula Weight(g mol1-) 490.85 486.64
Temperature (K) 296(2) 296(2)
Wavelength(Å) 0.71073 0.71073
Radiation type MoKα MoKα
Crystal system Monoclinic Monoclinic
Space Group C 2/c C 2/c
a (Å) 26.070(3) 8.5877(2)
b (Å) 7.4943(7) 11.1546(3)
c (Å) 33.390(3) 13.0772(4)
α (deg) 90 90
β (deg) 100.181(3) 104.955(2)
γ (deg) 90 90
V (Å3) 6421.1(11) 1210.27(6)
Z 12 2
ρcalc (g cm–3) 1.523 1.335
F(000) 3036 512
µ (mm–1) 1.299 1.035
Limiting indices; h, k, l -33≤h≤33 -10≤h≤10
-9≤k≤ 7 -14≤k≤12
-42≤l≤ 42 -16≤l≤16
Reflections: collected. 26148 4834
Reflectionsuniq 7017 4496
Data/restraints/parameters 7017/0/399 4834/300/4
R1, wR2 0.0500, 0.1105 0.0255.0.0611
min,max(eÅ–3) 0.583, +-0.794 0.28 +0.18
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32
Table 3.4: Structure refinement parameters of complexes 7a-8a
7a 8a
Formula C22H26CuN2O8 C14H24CuN2O6
Formula Weight(g mol1-) 509.99 379.89
Temperature (K) 296(2) 296(2)
Wavelength(Å) 0.71073 0.71073
Radiation type MoKα MoKα
Crystal system Monoclinic Monoclinic
Space Group C 2/c C 2/c
a (Å) 23.046(2) 19.5429(16)
b (Å) 7.8138(7) 8.4215(6)
c (Å) 12.3343(12) 11.5209(10)
α (deg) 90 90
β (deg) 90.351(5) 119.567(3)
γ (deg) 90 90
V (Å3) 2221.1(4) 1649.2 (2)
Z 4 4
ρcalc (g cm–3) 1.525 1.530
F(000) 1060 796
µ (mm–1) 1.035 1.356
Limiting indices; h, k, l -29≤h≤29 -24≤h≤23
-10≤k≤10 -10≤k≤10
-15≤l≤15 -12≤l≤14
Reflections: collected. 9119 9119
Reflectionsuniq 2525 2525
Data/restraints/parameters 2525/0/153 1622/3/118
R1, wR2 0.0525, 0.1340 0.0525, 0.1340
min,max(eÅ–3) 0.583, +-0.794 -0.794- 0.583
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33
Table 3.5: Structure refinement parameters of complexes 9a-10a
9a 10a
Formula C10H28CuN2O8 C10H24CuN2O8
Formula Weight(g mol1-) 367.88 363.85
Temperature (K) 296(2) 296(2)
Wavelength(Å) 0.71073 0.71073
Radiation type MoKα MoKα
Crystal system Monoclinic Orthorhombic
Space Group P 21/n P c c n
a (Å) 7.1368 (4) 6.6538(8)
b (Å) 12.3417 (6) 15.2032(18)
c (Å) 19.9037 (9) 15.274(2)
α (deg) 90 90
β (deg) 91.049 (2) 90
γ (deg) 90 90
V (Å3) 1752.83 (15) 1545.1(3)
Z 4 4
ρcalc (g cm–3) 1.394 1.564
F(000) 1.281 1.452
µ (mm–1) 780 764
Limiting indices; h, k, l 9≤h≤-15 -7≤h≤8
15≤k≤15 -12≤k≤19
-25≤l≤25 -19≤l≤18
Reflections: collected. 13740 1766
Reflectionsuniq 3851 1355
Data/restraints/parameters 3815/0/218 1766/4/107
R1, wR2 0.0369, 0.0948 0.0400, 0.0998
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Table 3.6: Structure refinement parameters of complex 11a
Complex 11a
Empirical formula C9H13ClCuN2O3
Formula weight 296.20
Temperature 296(2)
Wavelength 0.71073
Radiation type MoKα
Crystal system Monoclinic
Space group P21/c
a(Å) 13.9179 (10)
b(Å) 10.4900 (8)
c(Å) 8.5181 (6)
α() 90
() 105.518 (4)
γ() 90
Volume (Å3) 1198.30 (15)
Z 4
calc (g cm–3) 1.642
(mm–1) 2.038
F(000) 604
hkl ranges -17≤h≤17
-13≤k≤13
-8≤l≤10
Reflections collected 8951
Independent Reflections 2351
Data/ restraints/parameters 2612/0/149
R[F2> 2σ(F2)] 0.026
wR(F2) 0.069
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3.2.2 Single crystal X–ray structure determination for 1b and 2b
Intensity data were collected for the single crystals of (1b) and (2b), at 296 K, on a Bruker
SMART APEX-II CCD diffractometer using graphite monochromatedMoKα radiation (λ =
0.71073 Å). SAINT was used to refine the unit-cell and for data reduction [177]; data
reduction: SAINT; program(s) used to solve structure: SHELXS-97 (Sheldrick, 2008);
program(s) used to refine structure: SHELXL-97 (Sheldrick, 2008); [178]. Molecular
graphics were performed using programs: ORTEP-3 for Windows (Farrugia, 2012) and
PLATON (Spek, 2009); software used to prepare material for publication: WinGX (Farrugia,
2012) and PLATON [189-180]. Crystallographic data as well as details of data collection and
refinement for complexes 1b and 2b are presented in table 3.7.
Table 3.7: Structure refinement details for complexes 1b and 2b
Compound 1b 2b
Empirical Formula C28H24CuN2O5 C48H47ClCu2N8O11
Formula weight 532.03 1074.47
Crystal system Triclinic Orthorhombic
Space group 𝑃1̅ (No. 2) P212121(No. 19)
a (Å) 12.0357 (7) 13.5061 (10)
b (Å) 13.8799 (8) 18.1441 (11)
c (Å) 16.3225 (9) 18.9671 (13)
(°) 84.916 (3) 90
(°) 88.551 (3) 90
(°) 67.877 (3) 90
V (Å3) 2516.0 (2) 4648.1 (5)
Z 4 4
calc (g cm–3) 1.405 1.535
(mm–1) 0.909 1.044
Data collected 35228 21605
Unique data 10388 8839
RInt 0.044 0.039
R(F) [I> 2(I)] 0.060 0.039
wR(F2) [all data] 0.199 0.083
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3.2.3 Single crystal X–ray structure determinationfor 1c and 2c
Single crystal data collection for 1c and 2c was performed on a Bruker SMART APEX-II
CCD diffractometer using graphite monochromatedMoKα radiation (λ = 0.71073 Å) at 293
K. SAINT was used for the unit cell refinement and data reduction [177]. The structure was
solved by direct methods using SHELXS-97 and refined by full matrix least-squares against
|F|2 using SHELXL-97 [178]. Molecular graphics were performed using programs: ORTEP-
3 for Windows (Farrugia, 2012) and PLATON (Spek, 2009); software used to prepare
material for publication: WinGX (Farrugia, 2012) and PLATON [179-180]. The hydrogen
atoms were geometrically placed (C–H = 0.93 Å) and refined as riding atoms with Uiso(H) =
1.2Ueq(C). Crystal data and details of the data collection are given in Table 3.8. In the
complex 2c, the O3 atom of the water molecule of crystallization was found to be statistically
disordered over two adjacent sites related by inversion symmetry (O3⋯
C-bound H atoms were geometrically placed (C—H = 0.93 Å) and refined as riding atoms.
The N- and O-bound H atoms were located in difference maps: the positions of the N-bonded
H atoms were freely refined and the O-bonded H atoms were refined as riding atoms in their
as-found relative positions. The constraint Uiso(H) = 1.2Ueq(carrier) was applied in all
cases.
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Table 3.8: Structure refinement parameters of the complexes 1c and 2c
Compound 1c 2c
Empirical formula C26H18CuN2O4 C19H15ClCuN3O2½
Formula weight 485.90 424.33
Temperature (K) 293(2) 296(2)
Wavelength (Å) 0.71073 0.71073
Crystal system Monoclinic Monoclinic
Space group C2/c P21/n (No. 14)
a (Å) 21.2662(7) 9.8200(5)
b (Å) 9.9266(3) 10.9291 (7)
c (Å) 10.9599(3) 16.3803(9)
() 115.575(1) 105.293(3)
V (Å3) 2086.96(11) 1695.74 (17)
Z 4 4
calc (g cm–3) 1.547 1.662
(mm–1) 1.085 1.469
F(000) 996 864
2range () for data collection 2.77–28.30 5.56–53.0
hkl ranges –28 → 27, –13 → 12, –12 9; –13 13;
–14 → 14 –19 20
Reflections scanned 9910 12658
Independent reflections 2601 3493 (RInt = 0.047)
Data / restraints / parameters 2346 3493 / 0 / 259
R(F) [I> 2(I)] 0.026 0.043
wR(F2) 0.076 0.122
Min., max. (e Å3) –0.26, +0.33 –0.60, + 0.37
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3.3 Antimicrobial activity measurement (Agar well diffusion method)
3.3.1 Antimicrobial activity of complexes 1a-11a
The in-vitro antimicrobial activities of synthesized complexes [Cu(tmen)(BA)2(H2O)2], (1a)
[Cu(tmen)(salH)2(H2O)] (2a), {[Cu(tmen)(mef)2] (3a), [Cu(tmen)(pABA)2]. 1/2 MeOH(4a),
[Cu(tmen)(o-ClBA)2] (5a), [Cu(tmen)(cinn)2]. H2O (6a), [Cu(tmen)(phtH)2] (7a),
[Cu(tmen)(tpht)(H2O)2]n (8a), {[Cu(tmen)(succin)].4H2O}n (9a), {[Cu(tmen)(tart)]·2H2O}n
(10a)[Cu(en)(salH)Cl]n (11a) were tested by well diffusion method. The chosen strains were:
Bacillus spizizenii, Escherichia coli, Klebsiella pneumonia and Staphylococcus aureus.
Nutrient agar medium (Merck) was prepared by dissolving 25 g of nutrient agar powder in
one litre of distilled water in a conical flask. Its pH was adjusted to 7.00. The conical flasks
were plugged with cotton wool and were covered with aluminum foil. These were then
sterilized in an auto-clave for 15 minutes at 121°C. The fresh sterile nutrient broths (Merck)
were separately inoculated with bacterial strains, with the help of an inoculate wire loop from
slant cultures of respective microbes (Bacillus spizizenii, Escherichia coli, Klebsiella
pneumonia and Staphylococcus aureus). After incubation at 3