TY - JOUR
T1 - Electronic State and Photophysics of 2-Ethylhexyl-4-methoxycinnamate as UV-B Sunscreen under Jet-Cooled Condition
AU - Muramatsu, Satoru
AU - Nakayama, Shingo
AU - Kinoshita, Shin Nosuke
AU - Onitsuka, Yuuki
AU - Kohguchi, Hiroshi
AU - Inokuchi, Yoshiya
AU - Zhu, Chaoyuan
AU - Ebata, Takayuki
N1 - Funding Information:
This work was financially supported by the Institute for Quantum Chemical Exploration (T.E.), JSPS KAKENHI Grant Nos. JP19K05387 (T.E.), JP16H04098 (Y.I.), and JP19K15507 (S.M.). This work was also supported by the Ministry of Science and Technology, Taiwan (Grant Nos. MOST106-2113-M-009-016-MY3 and MOST108-2811-M-009-508). Calculations were partly performed using the Research Center for Computational Science, Okazaki, Japan.
Funding Information:
This work was financially supported by the Institute for Quantum Chemical Exploration (T.E.), JSPS KAKENHI Grant Nos. JP19K05387 (T.E.), JP16H04098 (Y.I.), and JP19K15507 (S.M.). This work was also supported by the Ministry of Science and Technology, Taiwan (Grant Nos. MOST106-2113-M-009-016-MY3 and MOST108-2811-M-009-508). Calculations were partly performed using the Research Center for Computational Science, Okazaki, Japan.
Publisher Copyright:
Copyright © 2020 American Chemical Society.
PY - 2020/2/20
Y1 - 2020/2/20
N2 - 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 ∼1010-1011 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 18 400 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*) → 1nπ∗ → T1 (3ππ*) → S0 (cis)".
AB - 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 ∼1010-1011 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 18 400 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*) → 1nπ∗ → T1 (3ππ*) → S0 (cis)".
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U2 - 10.1021/acs.jpca.9b11893
DO - 10.1021/acs.jpca.9b11893
M3 - Article
C2 - 31992045
AN - SCOPUS:85080846771
SN - 1089-5639
VL - 124
SP - 1272
EP - 1278
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 7
ER -