Temperature, pressure and solvent isotope effects on the precursor formation constant and reorganization dynamics in outer-sphere charge transfer between free mobile [Fe(CN)6]3– and [Fe(CN)6]4– ions
Abstract
Temperature (298–348 K), high-pressure (0.1–150 MPa) and solvent isotope (H2O/D2O) effects upon the maximum energy and absorption intensity of the outer-sphere metal–metal charge-transfer (MMCT) absorption band in encounter complexes of free mobile [Fe(CN)6]3– and [Fe(CN)6]4– ions have been investigated. ΔHA=(– 1.82 ± 0.05) kJ mol–1, ΔSA=(– 30.7 ± 1.4) J mol–1, K–1, and ΔVA=(– 1.0 ± 0.2) cm3 mol–1 have been obtained for the precursor formation of the absorbing species at 298 K and 0.1 MPa. The absorption maximum shifts by 120 cm–1 to higher energy upon increasing the temperature from 298 to 348 K while a decrease by 200 cm–1 has been observed in the pressure range 0.1–150 MPa. Replacement of H2O by D2O as the solvent results in a blue shift of the MMCT absorption maximum by 460 cm–1 without change in the intensity. Water molecules of the first solvation sphere, hydrogen bonded to the reactants, contribute considerably to the reorganization Gibbs energy of the optical transition.
Please wait while we load your content...
