Dynamics of the first excited state of the decatungstate anion studied by subpicosecond laser spectroscopy

The primary events in decatungstate photolysis are investigated by subpicosecond spectroscopy. Steady-state and picosecond fluorescence experiments are also reported. The absorption peak at 776 nm of the transient state called X, involved in photocatalytic reactions with organic substrates on the nanosecond time scale, rises in a few ps after subtle changes of an initial band, extending from the visible to the near-infrared (NIR). The decay in the NIR edge occurs in 25 ps in acetonitrile and 15 ps in water. X is interpreted as a delocalized ligand-to-metal charge transfer (LMCT) excited state, originating from a localized excited state absorbing in the NIR. Re-excitation of X could contribute to the 580 nm fluorescence observed under picosecond excitation.