Triplet excitation dynamics of β-carotene studied in three solvents by ns flash photolysis spectroscopy

Upon anthracene-sensitizing, triplet excitation dynamics of,beta-carotene (beta-Car) were studied in n-hexane, in methanol, and in acetonitrile, respectively, by ns flash photolysis spectroscopy. In n-hexane, only the bleaching of the ground state absorption (GSB) and the excitation triplet ((3)Car*) absorption were observed, and there were no cationic species detected. In both methanol and acetonitrile, similar excitation dynamics were observed, i.e., (3)Car* having a similar lifetime to that in n-hexane, and the immediate generation of the cation dehydrodimer ((#)[Car]2(+))upon excitation following transformation into the radical cation Car(center dot+), since Car(center dot+) has much longer lifetime in acetonitrile than in methanol. The results prove that both solvent and carotenoid structure determine the triplet excitation mechanism. (C) 2016 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.