Laser spectroscopic study on sinapic acid and its hydrated complex in a cold gas phase molecular beam

Excited-state dynamics of isolated and (micro)solvated methyl sinapate: the bright and shady sides of a natural sunscreen

“…The fast decay rates observed in the present experiments are puzzling since previous Laser Induced Fluorescence (LIF) and Dispersed Fluorescence (DFL) experiments reported fluorescence lifetimes of 12 and 14 ns at the electronic origins of conformers A and B, respectively [18]. On the other hand, ps pump-probe R2PI experiments on sinapic acid with a probe laser wavelength of 243 nm found for the syn/cis conformer at the origin transition a decay rate of (1.9 ns) −1 [29], which nicely follows what would be expected on the basis of the present experiments [47]. A further consideration is based on the radiative decay rate that is expected on the basis of Fermi's golden rule for vertical emission at an energy ω from the stable minimum of the S 1 state with an oscillator strength f (ω), which is given by…”

“…We then find that it lies about 6 kcal/mol above the minimum of the S 1 (V(ππ*)) state. It is interesting to notice that as a ballpark figure this number is in line with the energy that was calculated for the transition state in the S 1 state of MS in methanol ( ∼ 3 kcal/mol) [32], and for the transition state in the S 1 state of isolated sinapic acid ( ∼ 6 kcal/mol) [29], certainly when associating such a transition state with an (avoided) crossing with a higher-lying electronically excited state. It is also interesting to notice that this energy is roughly speaking in the range of the C = C stretch region for which we concluded above it has a reduced intensity to what was expected on the basis of Franck-Condon simulations.…”

“…Although these compounds have been known for a long time, highresolution laser spectroscopic studies on 2-ethylhexyl-4methoxycinnamate (EHMC) -the most common UV-B filter found in commercial sunscreens-led to the realisation that high-resolution studies in the frequency domain and time-resolved studies in the time domain can contribute significantly to the development of novel sunscreens [15][16][17]. As a result, recent years have witnessed a rapidly increasing interest in the detailed understanding of the spectroscopic properties of the electronically excited states of these compounds and their dynamics, and how to employ this knowledge to design and develop UV filters with improved properties [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”

Laser Spectroscopy and Lifetime Measurements of the S1 State of Tetracyanoquinodimethane (TCNQ) in a Cold Gas‐Phase Free‐Jet

“…These difficulties were overcome in our previous study by combining the high temperature or laser ablation nozzles for the generation of supersonic jet and LIF for the detection. We applied this method for cinnamic acids …”

“…The TCNQ sample, purchased from Tokyo Chemical Industry, was purified by recrystallization with acetonitrile/benzene before experimental use. The details of the experimental setup was described elsewhere,, and brief explanation is given in this communication. The supersonic free‐jet of TCNQ was produced by either of the two methods: (1) high temperature heating nozzle and (2) laser‐ablation nozzle.…”