MIDINFRARED SPECTRUM OF [RU(BPY)(3)](2+)

The first time-resolved infrared difference spectra for metal-to-ligan d charge transfer (MLCT) excited states in the fingerprint region from 1400 to 1625 cm(-1) are reported for [Ru(bpy)(3)](2+) and [Re(bpy)(C O)(3)(4-Etpy)](+) in CD3CN at 298 K (bpy is 2,2'-bipyridine; 4-Etpy i s 4-ethylpyridine). The spectra are assigned by comparison to ground-s tate spectra and electrochemically generated [RuIII(bpy)(3)](3+) and [ Ru-II(bpy(.-))(bpy)(2)](+). The data provide clear evidence for the lo calized description [Ru-III(bpy(.-))(bpy)(2)](2+) on the similar to 1 00 ns time scale. They also give insight into electronic distribution in the excited state based on the magnitudes and directions of the inf rared shifts.