A Systematic Approach To Methyl Cinnamate Photodynamics

Methyl cinnamate (MC) is an ester within the cinnamate family. Recent time-resolved gas-phase studies have suggested that upon excitation to its first singlet pi pi* (1(1)pi pi*) state, there is initial decay to the lowest lying singlet(1)n pi* (1(1)n pi*) state within 10 ps, en route totrans-cisisomerisation. In the present study, we have implemented time-resolved ion yield (TR-IY) and time-resolved photoelectron spectroscopy (TR-PES) experiments in the gas-phase to precisely determine the lifetime of the 1(1)pi pi* state. We found this lifetime to be similar to 4.5 ps using both TR-IY and TR-PES. MC was also studied in a more complex cyclohexane solution environment, using transient electronic absorption spectroscopy. Along with complementary steady-state irradiation and(1)H NMR studies, these studies demonstrate thattrans-cisisomerisation is preserved in the more complex, cyclohexane solution environment.