Electron transfer bridging ligand properties

Ondrechen et al. have presented the results of model system calculations of discrete, bridged donor-acceptor complexes, and also of related linear-chain and two-dimensional network systems. These calculations have demonstrated how the bridging ligand can modulate the electron transfer and conductivity properties of the system. 

Traditionally, electron transfer processes in solution and at surfaces have been classified into outer-sphere and inner-sphere mechanisms (1). However, the experimental basis for the quantitative distinction between these mechanisms is not completely clear, especially when electron transfer is not accompanied by either atom or ligand transfer (i.e., the bridged activated complex). We wish to describe how the advantage of using organometals and alkyl radicals as electron donors accrues from the wide structural variations in their donor abilities and steric properties which can be achieved as a result of branching the alkyl moiety at either the a- or g-carbon centers. 

Supramolecular Ru and/or Os complexes of tris(bipyridine) bridging ligands. Syntheses, absorption spectra, luminescence properties, electrochemical behavior, intercomponent energy, and electron transfer. [P. Belser, A. von Zelewsky, M. Frank, C. Seel, F. Vogtle, L. De Cola, F. Barigelletti, V. Balzani, J. Am. Chem. Soc. 1993, 225(10), 4076-4086] [ 23]. 

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