Transient enol isomers of dibenzoylmethane and avobenzone as efficient hydrogen donors toward a nitroxide pre-fluorescent probe.
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 (C343T) 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.
Aspée
Alexis
A
Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile. aaspee@usach.cl
Aliaga
Carolina
C
Scaiano
J C
JC
D000975:Antioxidants / Q000737:chemistry*; D047188:Chalcones / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D007536:Isomerism; D015336:Molecular Probe Techniques; D009589:Nitrogen Oxides / Q000737:chemistry; D010777:Photochemistry; D011427:Propiophenones
D000975:Antioxidants; D047188:Chalcones; D005456:Fluorescent Dyes; D009589:Nitrogen Oxides; D011427:Propiophenones; D006859:Hydrogen; C061481:dibenzoylmethane; C049935:avobenzone; C039900:nitroxyl