Abstract
AbstractTriplet‐triplet extinction coefficients for astaxanthin (I) and canthaxanthin (II) in different deaerated polarity solutions of MeCN and benzene were evaluated by laser flash photolysis at 298 K in the spectral region from 350 to 650 nm by energy transfer method, employing 2‐acetonaphthone as sensitizer. The triplet‐triplet extinction coefficients in MeCN and benzene were different in terms of the carotenoid present. The maximum triplet‐triplet extinction coefficient was 0.1–1.7×105 L·mol−1·cm−1 in different solvents. The rate constants of triplet decay were I: 1.25×1010 L·mol−1·s−1, II: 1.12×1010 L·mol−1·s−1 in MeCN; and I: 1.75×1010 L·mol−1·cm−1, II: 3.27×1010 L·mol−1·s−1 in benzene. The bimolecular rate constants of energy transfer from triplet excited 2‐acetonaphthone to carotenoids were determined from the linear regression of the decay rate constant of 2‐acetonaphthone triplet at varying carotenoid concentrations. The triplet lifetimes of 3AST* and 3CAN* in different solvents were also determined. The results indicated that triplet energy transfer was nearly diffusion‐controlled.
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