Analysis of superexchange coupling in metallocene-metallocenium redox pairs

Journal Article · Wed Mar 20 23:00:00 EST 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100159a039· OSTI ID:5637181

Newton, M D; Ohta, K; Zhong, E ^[1]

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1. Brookhaven National Lab., Upton, NY (United States)

Using a corresponding orbital approach implemented computational with the INDO method of Zerner et al, the authors have evaluated and analyzed the electron-transfer matrix elements (H{sub if}) for the ferrocene/ferrocenium and cobaltocene/cobaltocenium (Cp{sub 2}M/(Cp{sub 2}M){sup +}) electron exchange processes. Taking due account of the relative energies of different orientations of the reactants, they obtain good agreement with estimates of H{sub if} inferred from experimental kinetic data, as well as a detailed interpretation of the coupling based on a fully specified effective one-electron model. This model reveals distinct electronic mechanisms for the M = Fe and M = Co cases, corresponding, respectively, to superexchange of the 'electron' and 'hole' type. Variationally defined effective donor and acceptor orbitals are shown to be essentially equivalent to appropriately selected canonical molecular orbitals of the Cp{sub 2}M/(Cp{sub 2}M){sup +} transition-state complex. Departures from a simple one-electron model affect the calculated H{sub if} values by less than 10% (i.e., the many-electron core overlap integral is {approx gt} 0.9) even though the wave functions properly reflect the appreciable degree of electronic relaxation which is known to accompany the oxidation of the Cp{sub 2}M molecules. {sigma} as well as {pi}-type orbitals of the Cp rings are shown to play a significant role in facilitating the electronic coupling between reactants.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5637181
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:6; ISSN JPCHA; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKENES
CATIONS
CHARGED PARTICLES
CHEMICAL REACTIONS
COBALT COMPOUNDS
COMPUTER CALCULATIONS
CYCLOALKENES
CYCLOPENTADIENE
DATA
DIENES
ELECTRON TRANSFER
ENERGY LEVELS
HYDROCARBONS
INFORMATION
IONS
IRON COMPOUNDS
MATHEMATICAL MODELS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
POLYENES
REDOX REACTIONS
THEORETICAL DATA
TRANSITION ELEMENT COMPOUNDS