Electronic State and Photophysics of 2-Ethylhexyl-4-methoxycinnamate as UV-B Sunscreen under Jet-Cooled Condition.
J Phys Chem A
; 124(7): 1272-1278, 2020 Feb 20.
Article
en En
| MEDLINE
| ID: mdl-31992045
ABSTRACT
The title compound, 2-ethylhexyl-4-methoxycinnamate (2EH4MC), is known as a typical ingredient of sunscreen cosmetics that effectively converts the absorbed UV-B light to thermal energy. This energy conversion process includes the nonradiative decay (NRD) trans-cis isomerization and finally going back to the original structure with a release of thermal energy. In this study, we performed UV spectroscopy for jet-cooled 2EH4MC to investigate the electronic/geometrical structures as well as the NRD mechanism. Laser-induced-fluorescence (LIF) spectroscopy gave the well-resolved vibronic structure of the S1-S0 transition; UV-UV hole-burning (HB) spectroscopy and density functional theory (DFT) calculations revealed the presence of syn and anti isomers, where the methoxy (-OCH3) groups orient in opposite directions to each other. Picosecond UV-UV pump-probe spectroscopy revealed the NRD process from the excited singlet (S1 (1ππ*)) state occurs at a rate constant of â¼1010-1011 s-1, attributed to internal conversion (IC) to the 1nπ* state. Nanosecond UV-deep UV (DUV) pump-probe spectroscopy identified a transient triplet (T1 (3ππ*)) state, whose energy (from S0) and lifetime are 18â¯400 cm-1 and 20 ns, respectively. These results demonstrate that the photoisomerization of 2EH4MC includes multistep internal conversions and intersystem crossings, described as "S1 (trans, 1ππ*) â 1nπ* â T1 (3ππ*) â S0 (cis)".
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1
Colección:
01-internacional
Banco de datos:
MEDLINE
Idioma:
En
Revista:
J Phys Chem A
Asunto de la revista:
QUIMICA
Año:
2020
Tipo del documento:
Article
País de afiliación:
Japón