Interplay between Energy and Charge Transfers in a Polyaromatic Triplet Donor-Acceptor Dyad

摘要

We report the synthesis and photophysical characterization of a triplet donor-acceptor dyad (3), which was constructed from a quinoidal naphthalene thioamide triplet sensitizer 1 and a perylene derivative 2 as the acceptor. The dyad of interest exhibits convoluted photophysical characteristics from the donor and acceptor chromophores. The kinetic analysis of the phosphorescence of 3 produced two lifetimes tau(1) = 1.1 ms and tau(2) = 20 ms. The shorter component was attributed to the phosphorescence lifetime of the sensitizer (3)(1)* moiety (within the dyad) and the longer lifetime can be assigned to either the triplet state of the acceptor (3)(2)* or a charge transfer (CT)* species. This result was further corroborated with time-resolved transient absorption studies which revealed the CT band in the transient spectrum of the dyad. In this picture, the 1...2 interactions, which led to the formation of the CT species, was found to be the dominant photodynamics. Alternatively, dyad 3 was used to sensitize free perylene acceptor; the bimolecular (3)(3)* -> perylene triplet energy transfer allowed triplet-triplet annihilation based photon upconversion to generate anti-Stokes photoluminescence of perylene using a 532 nm excitation source.