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Photoexcited Singlet and Triplet States of a UV Absorber Ethylhexyl Methoxycrylene
Author(s) -
Kikuchi Azusa,
Hata Yuki,
Kumasaka Ryo,
Nanbu Yuichi,
Yagi Mikio
Publication year - 2012
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12017
Subject(s) - phosphorescence , intersystem crossing , electron paramagnetic resonance , excited state , singlet state , triplet state , chemistry , photochemistry , fluorescence , absorption (acoustics) , spectral line , singlet fission , atomic physics , nuclear magnetic resonance , physics , optics , astronomy
The excited states of UV absorber, ethylhexyl methoxycrylene ( EHMCR ) have been studied through measurements of UV absorption, fluorescence, phosphorescence and electron paramagnetic resonance (EPR) spectra in ethanol. The energy levels of the lowest excited singlet (S 1 ) and triplet (T 1 ) states of EHMCR were determined. The energy levels of the S 1 and T 1 states of EHMCR are much lower than those of photolabile 4‐ tert ‐butyl‐4′‐methoxydibenzoylmethane. The energy levels of the S 1 and T 1 states of EHMCR are lower than those of octyl methoxycinnamate. The weak phosphorescence and EPR B min signals were observed and the lifetime was estimated to be 93 ms. These facts suggest that the significant proportion of the S 1 molecules undergoes intersystem crossing to the T 1 state, and the deactivation process from the T 1 state is predominantly radiationless. The photostability of EHMCR arises from the 3 ππ* character in the T 1 state. The zero‐field splitting (ZFS) parameter in the T 1 state is D ** = 0.113 cm −1 .