Luminescence and excitation spectroscopy of ruthenocene

Abstract

The luminescence and excitation spectra of the perdeuterated and the protonated ruthenocene have been carefully investigated. The electronic origins are at 21 459 cm−1 and at 21 390 cm−1 for the perdeuterated and protonated crystals, respectively. The two observed luminescence progressions in the metal-ring stretch a′1 (D5h notation) in the perdeuterated crystal are separated by 155 cm−1 compared to the 165–170 cm−1 reported for the protonated compound. The metal-ring stretch frequency is reduced to 318 cm−1 in the perdeuterated crystal from the 333 cm−1 found for the protonated compound. In both crystals the observed doubling of the vibrational progression is due to a false origin based on a skeletal bending mode δ(ring-Ru-ring) which transforms as e1 in D5h. This mode is split by 7–8 cm−1 via the low site symmetry (Cs) in the crystal. The excitation spectrum of both compounds shows only a single progression in the metal-ring stretch. This frequency is reduced by 16% in the excited state for both the protonated and the perdeuterated crystal. Deuteration increases the lifetime from 127 μs to 990 μs at 1.5 K.