Photophysical characteristics of two model antenna systems: a fucoxanthin-pyropheoporbide dyad and its peridinin analogue

Photophysical investigations of a fucoxanthin-pheophorbide-alpha dyad and i ts peridinin analogue have revealed that the efficiency of carotenoid-to-ph eophorbide transfer of singlet excitation and of pheophorbide-to-carotenoid transfer of triplet excitation depend markedly both on the solvent and on the dyad, Furthermore, the carotenoid moiety, whose first excited singlet s tate lies higher than that of its pheophorbide partner, is able to quench t he fluorescence of the latter; such indirect quenching, which must entail a process other than the transfer of electronic excitation, might provide a channel for the dissipation of excess energy in some natural antenna system s. (C) 1999 Elsevier Science B.V. All rights reserved.