A systematic approach to methyl cinnamate photodynamics

Abstract

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* (1 1 ππ*) state, there is initial decay to the lowest lying singlet 1 nπ* (1 1 nπ*) 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 1 1 ππ* 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 1 H NMR studies, these studies demonstrate that trans-cis isomerisation is preserved in the more complex, cyclohexane solution environment.

Experimental and Computational Analysis of Para-Hydroxy Methylcinnamate following Photoexcitation

“…For MC, the same NRD process dominates with the 1 ππ*, 1 nπ* and 3 ππ* states having been experimentally observed. The observed lifetimes are also remarkably similar to p-CA, being 4.5 ± 1.1 ps and 20 ns for the 1 ππ* and 3 ππ* states, respectively [23,24]. In contrast, a study by Yamazaki et al for para-methoxy methylcinnamate (p-MMC), a close structural derivative of p-HMC, suggests that multistep intersystem crossing (ISC) from the 1 ππ* state to the 3 ππ* state could involve an intermediate 3 nπ* state [25].…”

“…The experimental setup has been described in detail elsewhere [23,33]. To briefly summarise, a Ti:Sapphire oscillator (Spectra-Physics Tsunami) and regenerative amplifier (Spectra-Physics Spitfire XP) are used to produce ∼40 fs laser pulses at a rate of 1 kHz and centred around 800 nm.…”

A post-HF approach to the sunscreen octyl methoxycinnamate

“…2,10, 13,14 More recently, experimental techniques such as ultrafast transient absorption spectroscopy, 22,23 both in the gas phase and in microsolvation environments, have been adopted for evaluating the fate of cinnamate-based organic filters under UV irradiation. [24][25][26] In particular, Tan et al 27 , by employing resonance two-photon ionization (R2PI), examined the photorelaxation behaviour of trans-octinoxate as isolated a) Electronic mail: gloria.tabacchi@uninsubria.it molecules in the gas phase and in microsolvation water environment. They ascribed the measured nanosecond-scale lifetimes in the gas phase to a long-lived 1 1nπ* state.…”

A Post-HF Approach to the Sunscreen Octyl Methoxycinnamate

“…However, the cis form has a lower absorption capacity than the trans isomer, hence a lower efficacy as a UVB filter. 2,10,13,14 More recently, experimental techniques such as ultrafast transient absorption spectroscopy, 22,23 both in the gas phase and in microsolvation environments, have been adopted for evaluating the fate of cinnamate-based organic filters under UV irradiation [24][25][26] . In particular, Tan et al 27 , by employing resonance two-photon ionization (R2PI), examined the photorelaxation behaviour of trans-octinoxate as isolated molecules in the gas phase and in microsolvation water environment.…”

“…2,10,13,14 More recently, experimental techniques such as ultrafast transient absorption spectroscopy, 22,23 both in the gas phase and in microsolvation environments, have been adopted for evaluating the fate of cinnamate-based organic filters under UV irradiation. [24][25][26] In particular, Tan et al 27 , by employing resonance two-photon ionization (R2PI), examined the photorelaxation behaviour of trans-octinoxate as isolated a) Electronic mail: gloria.tabacchi@uninsubria.it molecules in the gas phase and in microsolvation water environment. They ascribed the measured nanosecond-scale lifetimes in the gas phase to a long-lived 1 1nπ* state.…”