A deuterium perturbation upon electron transfer kinetics

Article abstract of DOI:10.1021/ja00147a017

¹H-NMR and X-band EPR were used to study the second-order rate constant for the electron transfer reactions involving naphthalene (C₁₀H₈) and perdeuterated naphthalene (C₁₀D₈) in the absence of ion association. In hexamethylphosphoramide the second-order rate constant for the intermolecular electron transfer from C₁₀D₈^·- to C₁₀D₈ [(6.4 ± 0.2) × 10⁸ M-¹ s^-1] is about 20% larger than it is for C₁₀H₈^·- + C₁₀H₈ = C₁₀H₈ + C₁₀H₈^·- (k_H-H/ k_D-D = 0.80). This is explained in terms of Marcus theory and the known 0.012 A? bond shortening that takes place when H is replaced by D in C₁₀H₈ and an estimated 0.02 A? bond shortening when H is replaced by D in C₁₀H₈^·-. The rate constants for electron transfer from C₁₀D₈^·- to C₁₀H₈ [(9.8 ± 0.1) × 10⁸ M^-1 s^-1] and from C₁₀H₈^·- to C₁₀D₈ (3.5 ± 0.6) × 10⁸ M^-1 s^-1] show that the electron transfer rates increase as the donor naphthalene is deuterated and the acceptor is protonated.