Solvent-dependent intra- and intermolecular vibrational energy transfer of W(CO)6 probed with sub-picosecond time-resolved infrared spectroscopy

Solvent-dependent intra- and intermolecular vibrational energy transfer from the triply degenerate CO stretch mode of W(CO)6 is observed in nine alkanes (CnH2n + 2, n = 5–13) with single-color sub-picosecond time-resolved infrared spectroscopy. In all the solvents, the vibrational relaxation process is well characterized by three time constants: τ1 (<1 ps), τ2 (3–13 ps) and τ3 (124–160 ps). The solvent dependence of τ2 and τ3 cannot be explained by the macroscopic properties of the solvent. In particular, the longest time constant τ3 shows the minimum value of 124 ps in decane among the nine alkanes. The rate of the vibrational energy relaxation is a sensitive measure of the microscopic environments.