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Eosin‐sensitized photoreduction of benzil with 1‐benzyl‐1,4‐dihydronicotinamide
Author(s) -
HuiJun Xu,
ShuYin Shen
Publication year - 1985
Publication title -
acta chimica sinica english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 0256-7660
DOI - 10.1002/cjoc.19850030210
Subject(s) - chemistry , benzil , eosin , photochemistry , eosin y , anthracene , quantum yield , excited state , singlet state , quenching (fluorescence) , triplet state , reaction rate constant , phosphorescence , electron transfer , fluorescence , kinetics , organic chemistry , molecule , catalysis , medicine , staining , physics , pathology , photocatalysis , quantum mechanics , nuclear physics
The mechanism of eosin‐sensitized photoreduction of benzil with 1‐benzyl‐1,4‐dihydronicotinamide — a model compound of NAD(P)H and the behavior of the excited states of eosin have been investigated. The effect of anthracene as a diffusion‐controlled quencher of the photoreaction indicates that both excited triplet state and an unquenchable excited singlet state of eosin participated in the sensitized photoreaction. From the Stern‐Volmer plot of quantum yield vs. anthracene concentration, the triplet reaction rate constant has been calculated to be 0.78 × 10 8 L M −1 S −1 while the singlet reaction rate constant determined from quenching of eosin fluorescence by benzil is equal to 7.2 × 10 9 L M −1 S −1 . The singlet and triplet quantum yields are also determined to be 0.09 and 0.18 respectively. Since both the singlet and triplet energies of eosin are lower than that of benzil, energy transfer sensitization is not feasible. It is proposed that electron transfer from the excited eosin to benzil is responsible for the initiation.