SYNTHESIS AND CHARACTERIZATION OF SOME TRANSITION METAL COMPLEXES AND THEIR REACTIVITY STUDIES

Abstract

Inorganic chemistry is the deep understanding of the synthesis, reactions, structures and properties of compounds of the elements. Inorganic chemistry has several branches and bioinorganic chemistry is one of them. Bioinorganic chemistry describes the mutual relationship between inorganic chemistry and biochemistry. This basically deals with the role of inorganic substances such as metal ions, composite ions, coordination compounds or inorganic molecules inside the living organism. Role of bioinorganic chemistry is to understand all the possible interactions between these inorganic substances and the biological tissues. These interactions can only be studied with the knowledge of coordination chemistry where metal ions bind with the ligands which could be the side chain of amino acid or any other biomolecule. Hence bioinorganic chemistry goes hand in hand with the coordination chemistry. In present study, the designing of few new ligands, their synthesis and characterization will be described. Manganese, iron, cobalt, nickel and copper complexes derived from those ligands and their spectroscopic studies will be described. Molecular structures of the few ligands and representative metal complexes were determined by X-ray crystallography. The results of reactivity studies on above mention metal complexes will be scrutinized in this thesis. The Thesis is divided into the following chapters. First chapter presents an introduction to coordination chemistry and several reactivity studies. The various chemical methods and spectroscopic techniques used were comprehensively summarized in this chapter. In chapter two, we have described Complexes [Cu(PyPhime-sali)ClO4] (1) and [Cu(PyPhime-tBu-sali(CH3OH))NO3].2CH3OH (2) (L1H2 and L2H2 (PyPhime-sali = 2,2'- v ((1E,1'E)(2,2'-(pyridine-2,6-diyl)bis(2-phenylhydrazin-2- yl1ylidene))bis(methanylylidene))diphenol, PyPhime-tBu-sali = 6,6'-((1E,1'E)-(2,2'- (pyridine-2,6-diyl)bis(2-phenylhydrazin-2-yl1ylidene))bis(methanylylidene))bis(2,4-di-tertbutylphenol) and H is dissociable proton) were synthesized and characterized by different spectroscopic methods. Molecular structures of the complexes were determined by X-ray crystallography and redox properties were investigated. Complex 1 was found to be a phenolato complex whereas complex 2 was a phenoxyl radical complex. Chapter three, describes hexacoordinated non-heme iron complexes [FeII(Cl-pyhyd- Pycarbo)2](ClO4)2 (3) and [FeII(Cl-pyhyd-methyl-Pycarbo)2](PF6)2 (4) have been synthesized using ligands [Cl-pyhyd-Pycarbo = (E)-2-chloro-6-(2-(pyridin-2ylmethylene) hydrazinyl)pyridine and Cl-pyhyd-methyl-Pycarbo = (E)-2-chloro-6-(2-(1-(pyridin-2- yl)ethylidene)hydrazinyl)pyridine]. These complexes are highly active non-heme iron catalysts to catalyse the C(sp3)−H bonds of alkanes. These iron complexes have been characterized using ESI−MS analysis and molecular structures were determined by X-ray crystallography. ESI−MS analysis also helped to understand the generation of intermediate species like FeIII−OOH and FeIV=O. These complexes have also been utilized in degradation of organic dyes. DFT and TD−DFT calculations revealed that the oxidation reactions were performed through high-valent iron centre and a probable reaction mechanism was proposed. These complexes were also utilized for the degradation of orange II and methylene blue dyes. In chapter four, copper complex [Cu(TETATA)(Cl2)] (5) derived from tridentate ligand (TETATA) (L=2-(2-((2-((2 aminoethyl)amino)ethyl)- amino)ethyl)isoindoline-1,3-dione) having NNN donor, was synthesized, characterized and molecular structure was determined using X-ray crystallography. This was found a robust vi catalyst for the degradation the organic dyes such as Orange II dye, Rhodamine B and Methylene blue. This catalyst was also utilised for the oxidation of catechol and 2- aminophenol. The catecholase and phenoxazinone synthase activity were determine using UV-visible spectroscopic studies. Theoretical calculations were performed to understand the electronic properties of this molecule. In chapter five, Bio-inspired [Mn(PyPhime-Pycarbo)(H2O)(CH3OH)](ClO4)2 (6) and [Fe(PyPhime-Pycarbo)(H2O)(ClO4)]ClO4 (7). Complexes with a pentadentate ligand (PyPhime-Pycarbo = 2,6-bis((E)-1-phenyl-2-(pyridin-2-ylmethylene)hydrazinyl)pyridine) framework containing N5 binding motif displayed excellent superoxide dismutase activity (SOD), with high stability in physiological conditions. In chapter six, Complexes [Mn(PyPhime-Cina)Cl2],(8) [Fe(PyPhime-Cina)Cl2] (9) [Co(PyPhime-Cina)Cl2] (10), [Ni(PyPhime-Cina)Cl2] (11) [Cu(PyPhime-Cina)Cl2] (12) have been synthesized using ligand (PyPhime-Cina=2,6-bis((E)-1-phenyl-2-((E)-3- phenylallylidene)hydrazinyl)pyridine) with NNN type moiety. The complexes have been used to studies the DNA interaction studies. Chapter seven presents the synthesis of complexes [Cu(PyPhime-Ben)2](NO3)2 (13), [Cu(PyPhime-Ben)2](ClO4)2 (14) using ligand PyPhime-Ben = 2,6-bis((E)-2-benzylidene-1- phenylhydrazinyl)pyridine and complexes of [Cu(PyPhime-p-methoxyBen)(PF)2] (15) and [Co(PyPhime-p-methoxyBen)Cl2] (16) using ligand PyPhime-p-methoxyBen = 2,6-bis((E)- 2-(4-methoxybenzylidene)-1-phenylhydrazinyl)pyridine these complexes were utilized for DNA interaction studies. Using tetradentate ligand (Gimpy = (1E,2E)-1,2-bis(2-phenyl-2- (pyridin-2-yl)hydrazono)ethane) we have synthesized eight coordinated [Mn(Gimpy)2](ClO4)2(17) and [Mn(Gimpy) (NO3)2](18) complexes. In this chapter we vii have utilised petadentate ligand L6 for [Co(PyPhime-Pycarbo)(H2O)(ClO4)](ClO4),(19), [Mn(PyPhime-Pycarbo)(H2O)2] (Fe(CN)5NO)(20) and [Ni2(PyPhime-Pycarbo)2Cl2] (ClO4)2,(21) complexes. These complexes have been synthesized and their molecular structure characterized with single crystal X- ray diffraction analysis. These complexes utilised for the in- vitro inhibition of superoxide anion i.e superoxide dismutase activity (SOD) studies. We have also synthesized complexes [Fe2(PyPhime-sali)2](Fe(CN)5NO) (22) and [Fe2(PyPhime-sali)2](ClO4)2 (23) using pentadentate ligand L1 for in- vitro superoxide dismutase activity (SOD) studies.