ABINITIO CALCULATION OF INNER-SPHERE REORGANIZATION ENERGIES OF INORGANIC REDOX COUPLES

Values of the inner-sphere reorganization energies (lambda(i)) for a number of small-molecule inorganic redox couples (NO+/NO, NO2+/NO2, NO2/NO2-, N3/N3-, O2/O2-, O3/O3-, SO2/SO2-, ClO/ClO-, ClO2/ClO2-, and Cl2/Cl2-) have been calculated by ab initio methods. The lambda(i) values were calibrated by comparing calculated bond lengths/angles, electron affinities, and ionization potentials with experimental data and were found to be accurate to within +/-2 kcal mol-1 or better. Classically calculated lambda(i) agreed well with the ab initio values, lending further credibility to previous conclusions regarding the electron-transfer chemistry of the redox species involved. In particular, the very high lambda(i) of NO2+/NO2 was reproduced by the ab initio calculations, thus explaining the low ET reactivity of nitronium ion toward organic compounds.