Time-Resolved IR Study of the Photobehavior of W(CO)₅(4-Acpy) (4-Acpy = 4-Acetylpyridine)

Fast time-resolved infrared spectroscopy (TRIR) is used to probe the photochemistry of W(CO)₅(4-acetylpyridine) in n-heptane. Visible irradiation (510 nm) populates the lowest MLCT state, which is monitored by TRIR. Subsequent dissociation to W(CO)₅⋯n-heptane, via equilibrium with the ³LF state, is also followed. On UV irradiation (308 nm), the LF state is populated directly and W(CO)₅⋯n-heptane appears immediately. With 510-nm irradiation, the yield of W(CO)₅⋯n-heptane as a function of temperature is measured to give a value for the energy gap between the lowest MLCT state and the ³LF state, −4000 cm⁻¹.