Time-resolved EPR study on reorganization energies for charge recombination reactions in the systems involving hydrogen bonding

Hydrogen bonding effects on reorganization energies (λ) in the photoinduced electron donor–acceptor system of duroquinone (DQ)–1,2,4-trimethoxybenzene (TMB) in benzonitrile have been investigated by time-resolved EPR and cyclic voltammetry measurements. The solvent reorganization energies (λS) determined for the radical ion pair systems involving the hydrogen-bonded complexes are larger by ∼0.2 eV than those calculated from the Marcus continuum dielectric model. The present results suggest that dissociation of the DQ anion–alcohol hydrogen-bonded complex results in the new component of λS for the charge recombination reaction in polar solvents.