Triplet Energy Transfer from Polymethine Dimers in the Complexes with Cucurbit[8]urils

Abstract

Effect of cucurbit[8]uril on the efficiency of triplet–triplet energy transfer between the donor dimer and the acceptor monomer or dimer has been studied. The efficiency depends on the rate constant of quenching of donor delayed fluorescence by the triplet energy acceptor, on the lifetime of the donor triplet state in the absence of a quencher, and on the acceptor concentration. Triplet–triplet energy transfer between the 3,3'-diethylthiacarbocyanine dimer (donor) and indodicarbocyanine (acceptor) occurs with a rate constant of 1.5 × 10⁸ L mol^–1 s^–1 . Replacing the indodicarbocyanine monomer by the thiadicarbocyanine dimer decreases the energy transfer rate constant by a factor of 4.5. In the case of the 3,3'-dimethylthiacarbocyanine dimer as a donor, the quantum yield of energy transfer to the indodicarbocyanine monomer decreases fourfold.