The mononuclear Ru(II) complex, cis -[Ru(tmp) 2 (CH 3 CN) 2 ](NO 3 ) 2 ?EtOH, where tmp is 3, 4, 7, 8- tetramethyl- 1, 10- phenanthroline, has been prepared and characterized by elemental analysis, spectroscopic methods (UV- Vis and FT-IR ) and single crystal X-ray structure analysis. This complex crystallized in the monoclinic crystal system with a space group of P 2(1)/c and the following unit cell parameters: a (?)= 11.1599(3), b (?)= 17.5396(4), c (?) = 19.0239(4), ? (?)= 90, ? (?)= 91.3210, ? (?)= 90, Z = 2 and V (? 3 ) = 3722.75(15). The X-ray analysis of the complex shows that the coordination geometry around the Ru(II) center is a distorted octahedral. Through two acetonitrile molecules in the cis positions and two bidentate tmp ligands. The interaction of the complex with fish sperm DNA (FS-DNA) has been monitored by UV- Vis, fluorescence titration and voltammetric (CV and DPV) techniques. In UV- Vis experiments a significant hypochromic shift in the ? ? ? * transition with red shift was observed upon addition of FS-DNA and the intrinsic binding constant ( K b = 1 × 10 3 M -1 ) was determined. The emission intensity of the complex in the presence of FS-DNA gradually quenched which implies the photoelectron transfer from the guanine base of DNA to the MLCT state of the complex. The results reveal that the complex binds to FS-DNA by a groove binding mode. Also, the electrocatalytic reduction of CO 2 to CO by cis -[Ru(tmp) 2 (CH 3 CN) 2 ](NO 3 ) 2 ?EtOH has investigated with cyclic voltammetry technique. The CV data showed that the multi-electron reduction of CO 2 was catalyzed by the metal complex and a mechanism was proposed for this multi-step reduction.
