Complex series [Ru(tpy)(dpk)(X)](n+) (tpy=2,2 ': 6 ',2 ''-terpyridine; dpk=2,2 '-dipyridyl ketone; X = Cl-, CH3CN, NO2-, NO+, NO center dot, 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 (v(NO), v(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-