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.