Electronic Excited States of [Au2(dmpm)3](ClO4)2 (dmpm= bis(dimethylphosphine)methane)

We present studies of the resonance Raman and electronic luminescence spectra of the [Au2(dmpm)3](ClO4)2 (dmpm = bis(dimethylphosphine)methane) complex, including excitation into an intense band at 256 nm and into a weaker absorption system centered about ∼300 nm. The resonance Raman spectra confirm the assignment of the 256 nm absorption band to a 1(dσ* → pσ) transition, a metal−metal-localized transition, in that ν(Au−Au) and overtones of it are strongly enhanced. A resonance Raman intensity analysis of the spectra associated with the 256 nm absorption band gives the ground-state and excited-state ν(Au−Au) stretching frequencies to be 79 and 165 cm-1, respectively, and the excited-state Au−Au distance is calculated to decrease by about 0.1 A from the ground-state value of 3.05 A. The ∼300 nm absorption displays a different enhancement pattern, in that resonance-enhanced Raman bands are observed at 103 and 183 cm-1 in addition to ν(Au−Au) at 79 cm-1 The compound exhibits intense, long-lived luminescence ...