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

Photophysical investigations of a fucoxanthin–pheophorbide-a dyad and its peridinin analogue have revealed that the efficiency of carotenoid-to-pheophorbide 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 state lies higher than that of its pheophorbide partner, is able to quench the 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 systems.