Photoinduced Electron Transfer in 2,5,8,11-Tetrakis-Donor-Substituted Perylene-3,4:9,10-bis(dicarboximides)

A series of electron donor-acceptor compounds based on substitution of perylene-3,4:9,10,bis(dicarboximide) (PDI) with four electron donors at the 2,5,8,11-positions were synthesized and characterized using femtosecond transient absorption spectroscopy. The distance between the PDI and the N,N-dimethylaniline or phenothiazine donors was varied using one or two phenyl groups. Photoexcitation of PDI results in rapid charge separation followed by charge recombination with time constants ranging from tens of picoseconds to nanoseconds. The electron transfer time constants are compared with those of the corresponding molecules in which the donor is attached to the PDI through its imide nitrogen atom. The electron transfer reactions through the 2,5,8,11-positions of PDI are generally much faster than those through the imide nitrogen positions, in concert with stronger donor electronic coupling to the PDI acceptor core and in contrast to substituents at the imide positions through which the HOMO and LUMO nodal planes pass.