Superexchange coupling mechanisms for electron transfer processes

Conference · Sat Dec 31 23:00:00 EST 1988

DOI:https://doi.org/10.1007/978-94-009-0489-7_14· OSTI ID:6094513

Newton, M. D.

Electron transfer matrix elements for electron exchange between various pairs of transition metal complexes in close contact have been calculated and analyzed for a variety of approach geometries for the two reactants. The coupling between the nominal metal ion donor/acceptor sites is achieved by superexchange of the ''hole'' type arising from ligand-to-metal charge transfer (LMCT), the dominant ligand-field interaction for the electron-donor ligands considered (H/sub 2/O, NH/sub 3/, and the cyclopentadienide anion). The pronounced variations of H/sub if/ with geometry are not correlated with the separation distance of the metal ions (between which the direct overlap is negligible) and span the range from non-adiabatic to strongly adiabatic electronic coupling. The values for metallocene/metallocinium redox pairs bracket recently reported experimental values. Analysis of the results using the method of corresponding orbitals demonstrates the validity of an effective 1-electron model for the electron transfer process to within about 10% for the class of systems considered. A higher-order superexchange mechanism was encountered for the Co(NH/sub 3/)/sub 6//sup 2+/3+/ exchange process, in which the LMCT-driven hole-transport mechanism couples excited local states of the metal ions, which in turn are connected to the corresponding ground states by spin-orbit mixing. This mechanism yields on electronic transmission factor within two orders of magnitude of unity. 30 refs., 5 tabs.

• Research Organization: Brookhaven National Lab., Upton, NY (USA)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 6094513
• Report Number(s): BNL-42831; CONF-8905146-1; ON: DE89013568
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
640304 -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
CALCULATION METHODS
CHARGE EXCHANGE
COUPLING
ELECTRON TRANSFER
ELEMENTS
FUNCTIONS
INTERMEDIATE COUPLING
L-S COUPLING
MATRIX ELEMENTS
METALS
WAVE FUNCTIONS