TY - JOUR
T1 - Multistep Intersystem Crossing Pathways in Cinnamate-Based UV-B Sunscreens
AU - Yamazaki, Kaoru
AU - Miyazaki, Yasunori
AU - Harabuchi, Yu
AU - Taketsugu, Tetsuya
AU - Maeda, Satoshi
AU - Inokuchi, Yoshiya
AU - Kinoshita, Shin Nosuke
AU - Sumida, Masataka
AU - Onitsuka, Yuuki
AU - Kohguchi, Hiroshi
AU - Ehara, Masahiro
AU - Ebata, Takayuki
N1 - Funding Information:
T.E., Y.I., M.E., and H.K. acknowledge Grants-in-Aid for Scientific Research (KAKENHI) by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Nos. 25410017, 16H04098, 16H04104, and 15KT0065, respectively. S.M., T.T., K.Y., and Y.H. acknowledge a grant from the Japan Science and Technology Agency with Core Research for Evolutional Science and Technology (CREST) in the Area of Establishment of Molecular Technology towards the Creation of New Functions at Hokkaido University.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/10/6
Y1 - 2016/10/6
N2 - The nonradiative decay pathways of jet-cooled para-methoxy methylcinnamate (p-MMC) and para-methoxy ethylcinnamate (p-MEC) have been investigated by picosecond pump-probe and nanosecond UV-Deep UV pump-probe spectroscopy. The possible relaxation pathways were calculated by the (time-dependent) density functional theory. We found that p-MMC and p-MEC at low excess energy undergo multistep intersystem crossing (ISC) from the bright S1 (1ππ∗) state to the lowest triplet T1 (3ππ∗) state via two competing pathways through the T2 state in the time scale of 100 ps: (a) stepwise ISC followed after the internal conversion (IC) from S1 to the dark 1nπ∗ state; (b) direct ISC from the S1 to T2 states. These picosecond multistep ISCs result in the torsion of C=C double bond by ∼95° in the T1 state, whose measured adiabatic energy and lifetime are 16577 cm-1 and ∼20 ns, respectively, for p-MMC. These results suggest that the ISC processes play an indispensable role in the photoprotecting sunscreens in natural plants.
AB - The nonradiative decay pathways of jet-cooled para-methoxy methylcinnamate (p-MMC) and para-methoxy ethylcinnamate (p-MEC) have been investigated by picosecond pump-probe and nanosecond UV-Deep UV pump-probe spectroscopy. The possible relaxation pathways were calculated by the (time-dependent) density functional theory. We found that p-MMC and p-MEC at low excess energy undergo multistep intersystem crossing (ISC) from the bright S1 (1ππ∗) state to the lowest triplet T1 (3ππ∗) state via two competing pathways through the T2 state in the time scale of 100 ps: (a) stepwise ISC followed after the internal conversion (IC) from S1 to the dark 1nπ∗ state; (b) direct ISC from the S1 to T2 states. These picosecond multistep ISCs result in the torsion of C=C double bond by ∼95° in the T1 state, whose measured adiabatic energy and lifetime are 16577 cm-1 and ∼20 ns, respectively, for p-MMC. These results suggest that the ISC processes play an indispensable role in the photoprotecting sunscreens in natural plants.
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U2 - 10.1021/acs.jpclett.6b01643
DO - 10.1021/acs.jpclett.6b01643
M3 - Article
AN - SCOPUS:84990864330
SN - 1948-7185
VL - 7
SP - 4001
EP - 4007
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 19
ER -