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

We have identified a new 3 MC 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 3 PES. This distal MC state (3 MCcis ) is destabilized by less than 2 kcal/mol with respect to the classical MC state (3 MCtrans ), and energy barriers to populate 3 MCcis and 3 MCtrans from the 3 MLCT state are similar according to nudged elastic band minimum energy path calculations. Distortions in the classical 3 MCtrans , 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 3 MCcis could be particularly relevant in the photodegradation of Ru(II) polypyridine complexes.