Monitoring Photochemical Reaction Pathways of Tungsten Hexacarbonyl in Solution from Femtoseconds to Minutes

Metal–organic complexes are widely used across disciplines for energy and biological applications, however, their photophysical and photochemical reaction coordinates remain unclear in solution due to pertaining molecular motions on ultrafast time scales. In this study, we apply transient absorption and tunable femtosecond stimulated Raman spectroscopy (FSRS) to investigate the UV photolysis of tungsten hexacarbonyl and subsequent solvent binding events. On the macroscopic time scale with UV lamp irradiation, no equilibrated intermediate is observed from W(CO)6 to W(CO)5(solvent), corroborated by vibrational normal mode calculations. Upon 267 nm femtosecond laser irradiation, the excited-state absorption band within ∼400—500 nm exhibits distinct dynamics in methanol, tetrahydrofuran, and acetonitrile on molecular time scales. In methanol, solvation of the nascent pentacarbonyl–solvent complex occurs in ∼8 ps and in tetrahydrofuran, 13 ps which potentially involves the associative oxygen-donating ligand re...