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G. Ayyannan:
"Synthesis, characterization and biological evaluation of palladium(II) complexes";
Betreuer/in(nen), Begutachter/in(nen): W. Linert, A. Chandramohan, C. Jayabalakrishnan; Inst. Applied Synthetic Chemistry, 2017; Rigorosum: 28.03.2017.

Coordination chemistry, a branch of inorganic chemistry plays a vital role in our daily life and is the most widely developing field in the last few decades. Synthesis of new metal complexes with structural design and properties analogous to anticancer agents is one of the most productive areas of coordination chemistry. Cisplatin, an effective anticancer drug in the treatment of a variety of tumors, has its own limitation due to resistance and the significant side effects such as nausea and kidney and liver failure typical of heavy metal toxicity. Hence, attempts are being made to replace this drug with more-efficient, less toxic, and target-specific non covalent DNA binding anticancer drugs. In the aspect of the metallic ion, because of the similar coordination modes and chemical properties of palladium(II) and platinum(II), they both form square planar complexes. On the basis of the structural and thermodynamic analogy between platinum(II) and palladium(II) complexes, much attention has been paid to palladium(II) compounds as potential anticancer agents. Palladium(II) complexes undergo aquation and ligand exchange reactions 105 times faster than the corresponding platinum(II) complexes. Furthermore, number of mixed ligand palladium(II) complexes are tested and proved to be an efficient compounds of antitumor drugs. Moreover, the DNA and protein interactions of metal complexes are more attractive for their potential application in medicine compared to small organic compounds because of their spectroscopic and redox properties. Ligands in these complexes play a major role in their binding to DNA. Hydrazone and thiosemicarbazone are a class of typical Schiff base compounds presenting a wide range of biological properties such as antibacterial, antioxidant, antiproliferative, anticonvulsant and antitumor. All the above facts have stimulated the interest to study the chemistry of palladium complexes containing various types of hydrazone and thiosemicarbazone ligands with triphenylphosphine and triphenylarsine as co ligands on DNA binding, protein interaction, antioxidant and cytotoxicity studies. The proposed thesis consists of six chapters. Chapter I gives a concise introduction about the scope and objective of the work and a detailed review of literature of relevant work on palladium complexes. Chapter II, deals with two new palladium(II) complexes (2 and 3) of 4-hydoxy-benzoic acid (5-bromo-2-hydroxy-benzylidene)-hydrazide (H2L) (1) with triphenylphosphine and triphenylarsine as coligand have been synthesized and characterized by the aid of various spectral techniques. The structure of the ligand and complexes was confirmed by single crystal X-ray diffraction studies. The hydrazone ligand acts as a tridendate ligand with ONO as the donor sites and is preferably found in the enol form in all the complexes. The structural analysis of 2 and 3 confirms the square planar geometry of the two complexes. The DNA binding of these complexes and ligand calf thymus DNA (CT-DNA) was investigated by using various methods, which revealed that the compounds interacted with CT-DNA through intercalation. Binding properties of the free ligand and its complexes with bovine serum albumin (BSA) protein have been investigated using UV-visible and fluorescence spectroscopic methods which indicated the stronger binding nature of the palladium complexes to BSA than the free hydrazone ligand. In addition, concentration dependent free radical scavenging potential of all the synthesized compounds (1-3) was also carried out under in vitro conditions. Further, the in vitro cytotoxicity of the compounds was examined on a HeLa and MCF-7 cell lines, which revealed that complex 2 exhibited a superior cytotoxicity than complex 3 and ligand 1. 2 Scheme