Dynamics and mechanism of radical formation in a highly sensitive oxime photoinitiator as revealed by time-resolved absorption and EPR measurements

被引：3
|
作者：
Sameshima, Kaori [1 ,2 ]
Kawakami, Tomomi [1 ]
Sotome, Hikaru [1 ]
Fuki, Masaaki [3 ]
Kobori, Yasuhiro [3 ]
Miyasaka, Hiroshi [1 ]
机构：
[1] Osaka Univ, Grad Sch Engn Sci, Div Frontier Mat Sci, Toyonaka, Osaka 5608531, Japan
[2] BASF Japan Ltd, Dev Display Mat, Amagasaki, Hyogo 6660081, Japan
[3] Kobe Univ, Grad Sch Sci, Dept Chem, Rokkoudai Cho,Nada Ku, Kobe 6578501, Japan
来源：
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY | 2023年 / 437卷
关键词：
Photoinitiator; Radical formation; Transient absorption spectroscopy; Time -resolved EPR; ELECTRON-SPIN POLARIZATION; BENZOYLOXYL RADICALS; SOLVENT POLARITY; QUANTUM YIELDS; PHOTOISOMERIZATION; PHOTODECOMPOSITION; DECARBOXYLATION; PHOTOCHEMISTRY; REACTIVITY; PHOTOLYSIS;
D O I：
10.1016/j.jphotochem.2022.114479
中图分类号：
O64 [物理化学（理论化学）、化学物理学];
学科分类号：
070304 ; 081704 ;
摘要：
Reaction dynamics and mechanism of radical formation of a photoinitiator, Irgacure OXE01, were investigated by transient absorption spectroscopy and time-resolved EPR measurements. Femtosecond transient spectroscopy revealed that the S1 state underwent ultrafast intersystem crossing and N-O bond cleavage with a time constant of 1.6 ps, resulting in the production of benzoyloxyl and iminyl radicals. The T1 state also yielded benzoyloxyl and iminyl radicals with a time constant of 300 ps. These radicals decreased in several ns time range by the geminate recombination in the radical pair in competition with the diffusional dissociation into free radicals. Time-resolved EPR measurement indicated that the radical pair produced from the T1 state effectively led to the production of the free radicals. These results strongly suggested the attractive potential via the exchange interaction between the two radicals in the pair suppressed the dissociation process of the radical pair.
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页数：9
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