Effect of charge delocalization on radical ion pair electronic coupling

Photoinduced charge separation and recombination were studied in a series of covalent donor–acceptor triads consisting of aniline, 1-aminonaphthalene, or 9-aminoanthracene donors (D) attached to a 4-aminonaphthalene-1,8-dicarboximide chromophore (ANI), which in turn is attached to a naphthalene-1,4:5,8-bis(dicarboximide) acceptor (NI) to give D–ANI–NI. The relationship between the molecular structure of D+ and the magnitude of the electronic coupling between the radicals within D+–ANI–NI− was probed by direct measurements of the spin–spin exchange interaction, 2J, using magnetic field effects on the yield of the neutral triplet state resulting from charge recombination and by density functional theory calculations.