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Published December 1, 2004 | public
Journal Article

Inner-Sphere Electron-Transfer Reorganization Energies of Zinc Porphyrins

Abstract

Inner-sphere electron-transfer reorganization energies of Zn(protoporphyrin IX) and Zn(octaethylporphyrin) are determined from band-shape analyses of the first ionization obtained by gas-phase valence photoelectron spectroscopy. The experimentally determined total inner-sphere reorganization energies for self-exchange (120−140 meV) indicate that structural changes upon oxidation are largely confined to the porphyrin ring, and substituents on the ring or solvent and other environmental factors make smaller contributions. Computational estimates by different models vary over a wide range and are sensitive to numerical precision factors for these low reorganization energies. Of current computational models that are widely available and practical for molecules of this size, functionals that contain a mixture of Hartree−Fock exchange and DFT exchange-correlation appear to be the most applicable.

Additional Information

© 2004 American Chemical Society. Received March 11, 2003. Publication Date (Web): November 5, 2004. We thank F. Ann Walker for providing the sample of Zn(oep). This work was supported by the NSF (CHE-0078809, H.B.G., J.R.W.; CHE-0078457, D.L.L.) and the DOE (DE-FG03-95ER14574, D.L.L.).

Additional details

Created:
August 19, 2023
Modified:
October 25, 2023