Mid-Infrared Spectrum of [Ru(bpy)₃]²⁺*

Abstract

The first time-resolved infrared difference spectra for metal-to-ligand 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)(CO)3(4-Etpy)]+* in CD3CN at 298 K (bpy is 2,2‘-bipyridine; 4-Etpy is 4-ethylpyridine). The spectra are assigned by comparison to ground-state spectra and electrochemically generated [RuIII(bpy)3]3+ and [RuII(bpy•-)(bpy)2]+. The data provide clear evidence for the localized description [RuIII(bpy•-)(bpy)2]2+* on the ∼100 ns time scale. They also give insight into electronic distribution in the excited state based on the magnitudes and directions of the infrared shifts.