MIDINFRARED SPECTRUM OF [RU(PHEN)(3)](2+)ASTERISK

Time-resolved infrared spectra in the fingerprint region (1300-1700 cm (-1)) are reported for the metal-to-ligand charge-transfer (MLCT) exci ted state(s) of [Ru(phen)(3)](2+) and [Os(phen)(DAS)(2)](2+)* (phen i s 1,10-phenanthroline; DAS is 1,2-bis(diphenylarsino)ethane) in aceton itrile-d(3) at 298 K. The spectra are assigned by comparison to electr ochemically generated [Ru-III(phen)(3)](3+) and [Ru-II(phen(.-))(phen) (2)](+). The data provide clear evidence for the localized description [Ru-III(phen(.-))(phen)(2)](2+) on the similar to 100 ns time scale. They also give insight into electronic distribution in the excited st ate, aid in the interpretation of the time-resolved resonance Raman sp ectrum of [Ru(phen)(3)](2+), and suggest why measuring ground- and ex cited-state resonance Raman spectra of phen complexes is difficult.