Laser-Induced Fluorescence of Decamethylrhenocene in Low-Temperature Matrices

Abstract

The emission and excitation spectra of decamethylrhenocene, Re(η5-C5Me5)2 have been recorded in argon and in nitrogen matrices with a tunable pulsed laser as exciting source. In argon matrices two sets of spectra may be excited selectively corresponding to different trapping sites or conformers of the guest molecules. Each set is dominated by a progression in ν8, a vibration corresponding to the in-phase combination of ring−metal−ring and ring−methyl bending modes (ν8‘ = 392 (2) cm-1 ν8‘‘ = 383 (1) cm-1). Much weaker features can be detected corresponding to progressions involving the three other totally symmetric modes (νx + nν8, x = 6, 7, 9, n = 0, 1, 2, ...). The emission and excitation bands in the principal site are symmetrical in shape with full width at half-maximum of only ca. 6 cm-1. The spectra of Re(η5-C5Me5)2 in nitrogen matrices are similar to those in argon matrices, but differ in site/conformer structure. The excited state lifetime in nitrogen matrices has been determined by single photon counting methods to be 3.69 (7) ns. The quantum yield for emission in nitrogen matrices is estimated as 0.010.