Ultrafast electron transfer reactions initiated by excited CT states of push–pull perylenes

Two new chromophores that absorb in the visible spectrum, the 9-(N-pyrrolidinyl)- and 9-(N-piperidinyl)perylene-3,4-dicarboximides, 5PMI and 6PMI, respectively, were synthesized and shown to possess lowest excited singlet states with about 70% charge transfer (CT) character. Changing the ring size of the cyclic amine from 5 to 6 significantly changes the energies of the CT states, as well as the redox potentials of the chromophores. These chromophores were linked to pyromellitimide (PI) and 1,8:4,5-naphthalenediimide (NI) electron acceptors using a single N–N bond between their respective imides to yield the corresponding donor–acceptor dyads 5PMI–PI, 5PMI–NI, 6PMI–PI, and 6PMI–NI. The donors and acceptors in these molecules are positioned relative to one another in a rod-like arrangement at fixed distances and restricted orientations. The rates of charge separation and recombination were measured using transient absorption spectroscopy. These chromophores were also used to prepare rigid donor–acceptor triads 5PMI–PI–NI and 6PMI–PI–NI, which display one- or two-step electron transfer mechanisms that depend on solvent polarity. These compounds exhibit a broad range of structure and media driven changes in electron transfer mechanism