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G. Raja:
"Synthesis, Characterizationand Applications Of Ruthenium(ii)/(iii) Schiff Base Complexes";
Betreuer/in(nen), Begutachter/in(nen): W. Linert, C. Jayabalakrishnan; Department of Chemistry, Bharathiar University, 2012; Rigorosum: 02.05.2012.

A branch of inorganic chemistry called coordination chemistry play a very important role in our daily life and it is the most widely developing field in the last few decades. In transition metal series, ruthenium plays a vital role in pharmaceutical chemistry. Ruthenium complexes containing Schiff base ligand are known to be biologically important and to serve as a catalyst in various chemical and photochemical reactions. Recent years have witnessed a great deal of interest in the synthesis and characterization of transition metal complexes of thiosemicarbazone and pyrazolone derivatives due to their interesting pharmaceutical properties. DNA binding metal complexes have been extensively investigated during the past several decades because they can be used as potential anticancer drugs, DNA structural probes, DNA-dependent electron transfer probes, DNA footprinting, sequence-specific cleavage agents and so on. In order to develop new potential DNA targeting antitumor drugs, the binding mechanisms of metal complexes to DNA should be further studied. Thus, it will be interesting and worthwhile to study the chemistry of ruthenium complexes containing various types of Schiff base containing thiosemicarbazide and 4-aminoantipyrine as antimicrobial, DNA binding and cleavage and anticancer agents. 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 ruthenium complexes. In chapter II, a group of new ruthenium(II) thiosemicarbazone complexes of the type [Ru(CO)(B)(L)] (where, B=PPh3/ AsPh3/Py; L= dibasic tetradentate Schiff base ligand), have been synthesized by reacting [RuHCl(CO)(PPh3)3], [RuHCl(CO)(AsPh3)3] and [RuHCl(CO)(Py)(PPh3)2] with the Schiff base in 1:1 molar ratio in ethanol-benzene mixture. These complexes have been characterized by elemental analysis, FT-IR, UV-Vis, NMR and mass spectroscopy. The redox behaviour of the complexes have been investigated by cyclic voltammetric technique. These complexes have been examined for their catalytic efficiency for aryl-aryl coupling and oxidation of primary and secondary alcohols into their corresponding aldehydes and ketones in the presence of molecular oxygen. All the complexes were screened for their antibacterial activity. Further, one of the complexes was tested for its binding with CT-DNA using absorption spectroscopic studies and viscosity measurements. Where R1=H/CH3; R2=H/C4H4; R3=H/OCH3; E=P/As; B=PPh3/AsPh3/Py Scheme 1. Formation of Ru(II) Schiff base complexes R3 R2 OH N R1 N C N H O + [RuHCl(CO)(EPh3)2(B)] Benzene-Ethanol Reflux, 6 h R3 R2 O N R1 N C S N H O Ru CO B SH 2 In chapter III, ruthenium(II) complexes are synthesized with Schiff bases derived from salicylaldehyde/o-hydroxyacetophenone/o-vanillin/2-hydroxy-1-naphthaldehyde with thiosemicarbazide and thiophenecarboxaldehyde. Ruthenium coordinate in a tetradendate manner with these N2O2 donor ligands, which was characterized by elemental analysis, IR, UV-Vis, 1H NMR, 13C NMR spectral studies. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). The redox behaviour of the complexes have been investigated by cyclic voltammetric technique in the potential range -2.0 to +2.0 V. All the complexes were tested for their antimicrobial activity against two bacteria and two fungi. Further, two of these complexes were analyzed for their binding with CT-DNA using absorption spectroscopic studies. Where R1=H/CH3; R2=H/C4H4; R3=H/OCH3; E=P/As; B=PPh3/AsPh3/py Scheme 2. Formation of Ru(II) Schiff base complexes Chapter IV deals with a series of new ruthenium(II) complexes were synthesized using Schiff base ligands derived from salicylaldehyde / o-hydroxyacetophenone / o-vanillin / 2-hydroxy-1-naphthaldehyde with thiosemicarbazide and acetyl furan. They are characterized by elemental analysis, IR, UV-Vis, 1H NMR and 13C NMR spectral studies. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). Four of these complexes were tested for their binding with CT-DNA using absorption spectroscopic studies and two of these complexes exhibit efficient DNA cleavage activity. Further, in vitro study of the cytotoxicity of [Ru(CO)(PPh3)L1] on HEp2 and HeLa were tested. The IC50 value for HEp2 and HeLa were 39.3 and 40.5 μm respectively. Where R1=H/CH3; R2=H/C4H4; R3=H/OCH3; E=P/As; B=PPh3/AsPh3/py Scheme 3. Formation of Ru(II) Schiff base complexes R3 R2 OH N R1 N C N H S + [RuHCl(CO)(EPh3)2(B)] Benzene-Ethanol Reflux, 6 h R3 R2 O N R1 N C S N H S Ru COB SH R3 R2 OH N R1 N C N O +[RuHCl(CO)(EPh3)2(B)] Benzene-Ethanol Reflux, 6 h. R3 R2 O N R1 N C S N O Ru COB SH 3 In chapter V, a Schiff base (HL) has been synthesized and characterized by physicochemical, spectroscopic and X - ray crystallography studies. Three of its Ru(III) complexes were synthesized and characterized by analytical and spectroscopic studies. The DNA binding properties of HL and its Ru(III) complexes have been investigated by electronic absorption spectroscopy. Also, HL and one of its complex [RuCl2(AsPh3)L] were tested for DNA cleavage properties. The results showed that the complex cleaves DNA more rapidly than the free ligand. Further, an in vitro study of the cytotoxicity of HL and the complex [RuCl2(AsPh3)L] was carried out. N N O N HC O Ru EPh3 X X N N O N HC OH + [RuX3(EPh3)3] Benzene-Ethanol Reflux, 6 h Wh ere, X = Cl or Br; E = P or As Scheme 4. Formation of Ru(III) Schiff base complexes Chapter VI presents the synthesis and characterization of three hexa-coordinated ruthenium(II) complexes of the type [RuCl(CO)(B)L] (B= PPh3/AsPh3/py and L= monobasic tridentate Schiff base ligand derived by the condensation of salicylaldehyde with 4-aminoantipyrine). The complexes were characterized by IR, electronic, NMR and mass spectral data. An octahedral geometry has been tentatively proposed for all the complexes. DNA binding properties of the ligand and its ruthenium(II) complexes have been investigated by electronic absorption spectroscopy. Two of the complexes were tested for DNA cleavage property. Finally, in vitro cytotoxicity study of the ligand and the complex [RuCl(CO)(PPh3)L] on HeLa was carried out and the IC50 value for the ligand and the complex were 52.3 and 31.6 μm respectively. N N O N HC O Ru B Cl CO N N O N HC OH + [RuHCl(CO)(EPh3)2(B)] Benzene-Ethanol Reflux, 6 h Where, E = P or As or py; B=PPh3 or AsPh3 or py Scheme 5. Formation of Ru(III) Schiff base complexes 4 The proposed thesis consists of summary at the end which describes the coordination mode and observations in the application studies.

Ru(III) Schiff base complexes, Ru(II) Schiff base complexes