Complex series [Ru(tpy)(dpk)(X)]n+ (tpy = 2,2':6',2'-terpyridine; dpk = 2,2'-dipyridyl ketone; X = Cl-, CH3CN, NO2(-), NO+, NO*, NO-): substitution and electron transfer, structure, and spectroscopy

The complex framework Ru(tpy)(dpk)]2+ has been used to study the generation and reactivity of the nitrosyl complex Ru(tpy)(dpk)(NO)]3+ (4]3+). Stepwise conversion of the chloro complex Ru(tpy)(dpk)(Cl)]+ (1]+) via Ru(tpy)(dpk)(CH3CN)]2+ (2]2+) and the nitro compound Ru(tpy)(dpk)(NO2)]+ (3]+) yielded 4]3+; all four complexes were structurally characterized as perchlorates. Electrochemical oxidation and reduction was investigated as a function of the monodentate ligand as was the IR and UV-vis spectroscopic response (absorption/emission). The kinetics of the conversion 4]3+/3]+ in aqueous environment were also studied. Two-step reduction of 4]3+ was monitored via EPR, UV-vis, and IR (nu(NO), nu(CO)) spectroelectrochemistry to confirm the {RuNO}7 configuration of 4]2+ and to exhibit a relatively intense band at 505 nm for 4]+, attributed to a ligand-to-ligand transition originating from bound NO-.