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Transient Enol Isomers of Dibenzoylmethane and Avobenzone as Efficient Hydrogen Donors toward a Nitroxide Pre‐fluorescent Probe †
Author(s) -
Aspée Alexis,
Aliaga Carolina,
Scaiano J.C.
Publication year - 2007
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 - 10.1562/2006-08-01-ra-992
Subject(s) - dibenzoylmethane , photochemistry , chemistry , flash photolysis , enol , fluorescence , reactivity (psychology) , quenching (fluorescence) , delocalized electron , adduct , double bond , organic chemistry , catalysis , kinetics , reaction rate constant , medicine , physics , alternative medicine , pathology , quantum mechanics
Abstract Dibenzoylmethane and avobenzone photochemistry involves the formation of transient enol isomers ( Z and E ). Conjugation of the OH group with the carbonyl group in these transient isomers reduces the OH bond energy. A fast reduction of the pre‐fluorescent probe (C 343 T) was observed after addition to photolysed DBM samples in nonpolar solvents. This can be attributed to a hydrogen transfer reaction from the transient E accumulated. While no quenching for Z by TEMPO was detected in the laser flash photolysis timescale. Theoretical calculations of spin densities distribution of the radical formed from Z and E showed a more delocalized distribution that would indicate a low reactivity towards oxygen. Our results suggest that DBM and avobenzone can effectively behave as photoantioxidants or photoactivated antioxidants under conditions where its enol isomers can be accumulated.