TRANSITION METAL COMPLEXES, PRECURSORS FOR CATALYTIC AND BIOLOGICAL APPLICATIONS

This study deals with the complexes of Cu(I/II) and Pd(II) with N,S and N,O ligands. Main focus of the study was the residual MCl (CuCl, CuCl2 CoCl2, ZnCl2 and PdCl2 ) functionality in final products. In some cases the reactions did not afforded the desired products and in most of the reactions the desired target was achived. The reactions were validated by repeating and using other metals in some cases such as Co(II), Zn(II) and Ni(II). Three principle series of ligands (O,N- and S,N-donor) were designed and synthesized and their reactions with salts containing metals like Cu and Pd were carried out under different reaction conditions. The ligands with O,N donor sites derived from pyridine-2,6-carbonyldichloride. Derivatization of 2,6-Pyridinedicarbonyl dichloride, thiophene-2,5-dicarbonyl dichloride and phenyl(chloro)dithiofarmate was carried out by treating them with pyrazole (1,4,7), 3methylpyrazole (2,5,8) and 3,5-dimethylpyrazole (3,6,9). These reactions led to the desired products as a result of HCl elimination in the presence of catalytic amount of trimethylamine at room temperature. The aminopyridinato ligand (12) was synthesized by treating the Grignard reagent derived from 2-bromo-6-(2,6-dimethylphenyl)pyridine formed in situ, with 2,6dibromopyridine in the presence of [NiBr2(DME)] (DME = 1,2-dimethoxyethane) and tricyclohexylphosphane (1:2 ratio). The reaction led to the corresponding monoarylated bromopyridines. The bromopyridine derivative undergos Pd-catalysed aryl amination (Buchwald?Hartwig amination) with 2,6-diisopropylaniline give rise to the expected compound 12. The compounds 1-3 and 7-9 were colorless solid crystalline material and their structures were determined with the help of X-ray diffraction while compounds 4-6 were obtained in liquid state. The solid state structures reveal that short range intermolecular interactions afford 1D (1,8) and 2D (2,3) supra-molecular chains, respectively. All novel compounds were also characterized with the help of Elemental analysis and NMR (1H and 13C) spectroscopy. The solution state structures were compared with solid state structures. The pyrazolyl drivitives of Pyridine-2,6-dicarbonyl dichloride upon treating with Cu(CH3COO)2.H2O in aqueous medium give complexes 13-15 due to the in situ dissociation of 13. The resultant complexes were characterized by elemental analysis and single crystal XRD. The set of data obtained for these complexes showed that MOFs were afforded (13 and 14) while mononuclear heterolyptic complex (15) as a result of in situ dissociation of the corresponding ligand was obtained. Precursors 4-6 were oily products and were characterized with the help of 1H- and 13CNMR spectroscopy. These ligands were soluble in common organic solvents. They were further treated with CuCl salt to give complexes 16 and 17, the structure of these complexes were confirmed with the help of X-ray diffraction and elemental analysis. These compounds give bimetalic crystalline copper complexes, 16 and 17 with monoclinic and triclinic geometry, respectively. Ligands 4-6 were treated with PdCl2 salt in acetonitrile and complexes 18-20 with PdCl2 residual functionalities were formed in essentially quantitative yield. The ligands were found to be N,S-bidentate linkers and 5-membered copper and palladacycles were obtained. Reaction of ligand 4 with Ni(II) salt suffers from in situ dissociation of the ligand followed by rearrangement into monoanionic ligand. The rearranged ligand is attached to metal centre in the ratio 2:1 (ligand:metal) and metallacycle 21 was afforded. Due to partial solubility of Pd and Ni complexes, complete set of NMR could not be collected, 18 (1H and 13C), 19, 20, 21b (1H). While single crystal analysis of complexe 18, 19 and 21 was carried out. The results reveal that compound 18 bears triclinic geometry while compounds 19 and 20 are monoclinic. The aminopyridinato ligand 12 was used for the synthesis of complex 22 containing CuCu bond and mononuclear cobalt complex 23. Complexes 22 and 23 were completely characterized with the help of NMR spectroscopy, elemental analysis and single crystal analysis. The results thus revealed that Cu-Cu bond exists in the corresponding binuclear complex having a separation of 2.450 Å . When CoCl2 was treated with aminopyridinato ligand in the same way as complex 22, the resultant complex was a homolyptic rather than bimetallic containing Co-Co bond. The reactivity of Cu-Cu bond with group 15, 16 and 17 elements amazingly gave no results, and showed tremendous stability. Complexes of M(II) with 3-methylpyrazole as ligand were prepared at ambient temperature using MCl2 salts (M = Cu, Co, Pd and Zn). All reactions were straight forward and no appreciable amount of side products was detected. X-ray structures were determined for all the complexes. The structures reveal that 28 and 29 possess Octahedral geometry, while 22 and 23 are square planar and tetrahedral, respectively. The synthesized compounds 28-31 have the MCl2 fragment, thus making the synthesized compounds attractive synthons for further transformations. The cyclic voltammetric investigations indicate the involvement of proton during electron transfer reactions of these complexes. The cyclic voltammograms of the synthesized complexes were obtained and the voltammetric signatures of 28, 29, and 31 showed a single irreversible pHdependent cathodic peak, while 30 gives two reversible cathodic peaks. Involvement of protons accompanying the electron transfer processes was ascertained from differential pulse voltammetric results, indicating peak potential shift as a function of pH. From the results it can be concluded that 15, 28, 29 and 31 show irreversible cathodic peaks so these complexes may be used as good anticancer agents. The ligands 1-3 and their complexes were tested against different strains of bacteria as antibacterial agents. The results reveal that ligands possess good inhibition activities compared to their respective complexes. While complex 15 was studied as representative example for DNA bonding potency using Cyclic Voltametric technique. The complexes 16-20 were also tested for their catalytic activity in Suzuki-coupling reactions, the complexes having palladium as central metal atoms show some how high catalytic activities as compared with other complexes. The activity is too low which hinders further studies and use of these complexes for commercial purpose