Exploration of Uncharted 3PES Territory for [Ru(bpy)3]2+: A New 3MC Minimum Prone to Ligand Loss Photochemistry.

We have identified a new 3MC state bearing two elongated Ru-N bonds to the same ligand in [Ru(bpy)3]2+. This DFT-optimized structure is a local minimum on the 3PES. This distal MC state (3MCcis) is destabilized by less than 2 kcal/mol with respect to the classical MC state (3MCtrans), and energy barriers to populate 3MCcis and 3MCtrans from the 3MLCT state are similar according to nudged elastic band minimum energy path calculations. Distortions in the classical 3MCtrans, that is, elongation of two Ru-N bonds toward two different bpy ligands, are not expected to favor the formation of ligand-loss photoproducts. On the contrary, the new 3MCcis could be particularly relevant in the photodegradation of Ru(II) polypyridine complexes.