trans-[Ru(16-TMC)(C N)(2)] (1; 16-TMC = 1,5,9,13-tetramethyl-1,5,9,13-tetraazacyclohexadecane) was prepared by the reaction of trans-[Ru(16-TMC)Cl-2]Cl With KCN in the presence of zinc powder. The oxidation of 1 with bromine gave trans-[Ru(16-TMC)(C N)(2)](+) isolated as PF6 salt (2-PF6). The Ru-C/C-N distances are 2.061(4)/ 1.130(5) and 2.069(5)/1.140(7) angstrom for 1 and 2, respectively. Both complexes show a Ru(III/II) couple at 0.10 V versus FeCp2+/0. The UV-vis absorption spectrum of 1 is dominated by an intense high-energy absorption at lambda(max) = 230 nm, which is mainly originated from d(pi)(Ru-II) -> pi*(N C-Ru-C N) charge-transfer transition. Complex 2 shows intense absorption bands at lambda(max) <= 228 nm and weaker vibronically structured absorption bands with peak maxima at 315-441 nm (epsilon(max) approximate to (5-8) x 10(2) dm(3) mol(-1) cm(-1)), which are assigned to d(pi)(Ru-III) -> pi*(N C-Ru-C N) and sigma(-C N) -> d(Ru-III) charge-transfer transition, respectively. Density functional theory and time-dependent density-functional theory calculations have been performed on trans-[(NH3)(4)Ru(C N)(2)] (1') and trans-[(NH3)(4)Ru(C N)2](+) (2') to examine the Ru-cyanide interaction and the nature of associated electronic transition(s). The 230 nm band of 1 has been probed by resonance Raman spectroscopy. Simulations of the absorption band and the resonance Raman intensities show that the nominal nu(C N) stretch mode accounts for ca. 66% of the total vibrational reorganization energy. A change of nominal bond order for the cyanide ligand from 3 to 2.5 is estimated upon the electronic excitation.