Ultrafast luminescence in Ir(ppy)3

A femtosecond luminescence and transient absorption study of fac-tris(2-phenylpyridine) iridium(III) [Ir(ppy)(3)] is reported. An emission with a lifetime component of 230 fs in the spectral region 500-560 nm is assigned to the population equilibration between electronic substates of the lowest excited triplet state, with energy dissipation by intramolecular vibrational redistribution. At shorter wavelengths a strong emission with a faster decay was observed and is attributed to a state with a higher admixture of singlet character. A slower decay on a 3 ps time scale is attributed to vibrational cooling. The results contribute to an understanding of the photophysics of transition metal complexes. (C) 2007 Elsevier B.V. All rights reserved.