Dielectric dispersion in optical electron transfer in solution

Free energies for photoelectron emission by aqueous solutions of hexaquo cations (V2+, Cr2+, Fe2+), metal complexes [Fe(CN)4−6, Co(NH3)2+6], and inorganic anions (OH−, Cl−, Br−, I−) are calculated from theory and compared with experimental threshold energies. Good agreement is obtained within the estimated error (±0.2 eV) on emission free energies. The free energy for outer-sphere reorganization is calculated from a continuous medium model. The inner-sphere reorganization energy is obtained from a bond-stretching model for hexaquo cations and metal complexes. A new method is developed for the calculation of the inner-sphere reorganization energies of univalent anions from their free energies of hydration. Reorganization free energies for electron transfer reactions [V2+/3+, Cr2+/3+, Mn2+/3, Fe2+/3+, Fe(CN)4−/3−6 ] calculated from experimental threshold energies and computed outer-sphere reorganization free energies yield activation free energies in agreement with the values obtained from kinetic measurements. Improvements are discussed for the determination of threshold energies by extrapolation.

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Dispersion spectroscopy of optical electron transfer in solution

Delahay

Dziedzic

1984

The Journal of Chemical Physics

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The effect of dielectric dispersion of the solvent on optical electron transfer is interpreted as a shift ΔGd of the free energy level of the ground state in the photoionization process. The shift ΔGd is derived for transparent and absorbing solvents by application of the Marcus theory of nonequilibrium polarization of a continuous medium. Only the inner-sphere solvation shell contributes significantly to the dispersion correction ΔGd. Application is made to photoelectric emission by solutions. The effect of dispersion on the energetics of emission causes deviation from the expected emission law. The resulting dispersion spectra are obtained for photoelectron emission by 17 inorganic anions in aqueous solution in the 7 to 10 eV range of photon energies. The spectra primarily result from dispersion of the solvent and are not strongly affected by the nature of the photoionized anion. Experimental dispersion spectra agree well with the theoretical spectrum predicted from the real and imaginary dielectric constants obtained from reflectance spectroscopy data of liquid water. Dispersion spectroscopy of optical electron transfer developed in this work provides an experimental probe of the inner-sphere solvation shell.

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Dielectric dispersion in optical electron transfer in solution

Cited by 4 publications

References 20 publications

Electron Transfer: General and Theoretical

Electron Transfer: General and Theoretical

Inner-sphere reorganization in optical electron transfer

Dispersion spectroscopy of optical electron transfer in solution

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