In this thesis, two mononuclear complexes of Zn(II) and Ru(II), [Zn(dmb) 3 ](PF 6 ) 2 and trans -[Ru(dmb) 2 (EtOH)Cl]PF 6 , (dmb = 4, 4´-dimethyl-2, 2´-bipyridine) have been prepared and characterized by elemental analysis, FT-IR and UV-vis spectroscopies. crystals of [Zn (dmb) 3 ](PF 6 ) 2 Crystal structure showed which the coordination geometry around the Zn (II) was a distorted octahedral. The dmb ligands are coordinated to Zn (II) ions through two nitrogen atoms. Brown crystals of trans -[Ru(dmb) 2 (EtOH)Cl]PF 6 were grown by ether diffusion into a acetonitrile solution of the complex. This complex was crystallized with the following unit-cell parameters: a (?) = 15.04, b (?) = 11.524, c (?) = 16.288, ? (?) = 90, ? (?) = 90, ? (?) = 90, Z = 4 and V (? 3 ) = 2823.1. Single crystal structure showed that the coordination geometry around the Ru (II) was a distorted octahedral. The FT-IR spectra of these complexes showed that bands are shifted and their intensity are changed in comparison with free dmb ligand. The interaction of the trans -[Ru(dmb) 2 (EtOH)Cl]PF 6 and [Zn(dmb) 3 ](PF 6 ) 2 complexes with DNA was investigated by UV-vis and fluorescence Spectroscopies, cyclic voltammetry and gel electrophoresis. Absorption spectra titrations of these complexes with fish DNA suggest that these complexes bind to DNA. The magnitude of the binding constant (K b ) was obtained from absorption spectra titration. All the results showed the majority of interaction mode between the complex and DNA was electroestatic. An in vitro cytotoxicity study of the [Zn(dmb) 3 ](PF 6 ) 2 , trans -[Ru(dmb) 2 (EtOH)Cl]PF 6 and [Ru(phen-diox) 3 ](PF 6 ) 2 ,(phen-diox = 2,3-dihydro-4a,12b-(epoxyethanooxy)[1,4]dioxino[2,3-f][1,10]phenanthroline) complexes on human breast adenocarcinoma (MCF7) cell line by an MTT assay indicated that these complexes may have anticancer potency with a cytotoxicity value of 0.96±1.69 µM, 0.6± 1.14 µM and 7.96±1.8µM,respectively and DNA cleavage experiments showed that these complexes induce cleavage of pTZ57 DNA plasmid DNA. The electrocatalytic reduction of CO2 to CO by trans -[Ru(dmb) 2 (EtOH)Cl]PF 6 was investigated using cyclic voltammetry in CH3CN solution. Thedetailed reaction mechanism and intermediates structures for the electrocatalytic reduction were also studied with the aid of density functional theory (DFT).