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 ππ* (11ππ*) state, there is initial decay to the lowest lying singlet 1nπ* (11nπ*) state within 10 ps, en route to trans–cis isomerisation. 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 11ππ* state. We found this lifetime to be ∼ 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 1H NMR studies, these studies demonstrate that trans–cis isomerisation is preserved in the more complex, cyclohexane solution environment.