Efficient Generation of the Ligand Field Excited State of Tris-(2,2‘-bipyridine)-ruthenium(II) through Sequential Two-Photon Capture by [Ru(bpy)3]2+ or Electron Capture by [Ru(bpy)3]3+

The relaxation dynamics and product distribution resulting from the decay of high lying excited states generated via sequential two-photon capture by [Ru(bpy)3]2+ or electron capture by [Ru(bpy)3]3+ have been investigated by flash photolysis and pulse radiolysis techniques. In comparison to the decay dynamics for monophotonic excitation, dramatically different relaxation dynamics have been observed. High-power flash excitation yields both the lowest lying metal-to-ligand charge transfer (3MLCT) state and a new transient photoproduct associated with nonradiative decay through the photodissociative metal-centered (3dd) excited state/s. The photoproduct is postulated to be [RuII(bpy)2(η1-bpy)]2+ where the pendant pyridine has rotated to yield a transient that is stabilized by a π−bonded or a three-centered Ru−C−H agostic interaction.