In this thesis, a new mononuclear polypyridyl ruthenium(II) complex, [Ru(dmbpy)(tptz)(Cl)](PF 6 ) (where dmbpy = 4,4'-dimethyl-2,2'-bipyridine, and tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine), has been prepared and characterized by elemental analysis, IR, 1 H NMR, UV-vis, and X-ray crystallography. The solid-state structure of the complex shows that tptz and dmbpy are coordinated to the ruthenium center as tridentate and bidentate ligands, respectively. The monodentate chloro ligand occupies the sixth coordination site in the complex. The central chromophore, RuN 3 N 2 ?Cl, has a distorted octahedral geometry. The electrochemical behavior of the complex was studied using cyclic voltammetry method and the results indicated a metal-based redox couple, Ru(III/II), in the positive potential and quasi-reversible couples for the polypyridyl ligands in the negative potentials. In addition, the electrocatalytic activity of the complex for the reduction of CO 2 to CO was investigated by cyclic voltammetry. The results show a two- electron reduction of CO 2 in the presence of the complex. According to the theoretical calculations by the Gaussian G09 software and using DFT techniques as well as the experimental data, a proper mechanism for the CO 2 reduction reaction was proposed. Also, the electrocatalytic behavior of the complex has been investigated under different reaction conditions, viz. , different concentrations of the complex, different purging times, and different temperatures of the electrochemical cell. The results indicated that the best electrocatalytic efficiency for the reduction of CO 2 to CO can achieve in 2 mM complex, purging time of 30 min, and cell temperature of 20 °C.