Spectroscopic Evidence for the Nature of the Excited States of the Ru(bpy)²⁺₃System

An overview of the recent developments in the spectroscopy of the Ru(bpy)2+ 3 (bpy=2,2′-bipyridine) system is given. Particular interest lies in the nature of the charge transfer excited states, and an appraisal of various excited state properties, as determined by experiment, is put forward. The validity of the interpretations of some of these experiments is discussed and is related to prevailing current ideas such as “exciton hopping,” “spatially isolated orbitals” and the concept of “localization” in general. On balance, it is suggested that the best initial description of the excited states involves the ligands equivalently, the excitation being fundamentally delocalized. Suggestions are made towards definitive experiments in this area.