Picosecond dynamics of nonthermalized excited states in tris(2,2-bipyridine)ruthenium(II) derivatives elucidated by high energy excitation.

The picosecond excited-state dynamics of several derivatives have been investigated using high photon energy excitation combined with picosecond luminescence detection. Instrument response-limited fluorescence (tau(1) approximately equal to 3-5 ps) at 500 nm was observed for all of the complexes, while longer-lived emission (tau(2) > 50 ps), similar in energy, was observed for only some of the complexes. Interestingly, the presence of tau(2) required substitution at the 4,4-positions of the bipyridine ligands and D(3) symmetry for the complex; only the 4,4-substituted homoleptic complexes exhibited tau(2).