Intervalence electron transfer in bicobaltocene cations: comparison with biferrocenes

摘要: Abstract : The near-infrared absorption parameters for bicobaltocene monocation, (Cp2Co)2+, evaluated in several solvents, are compared with corresponding data biferrocene cation, (Cp2Fe)2+, order to ascertain the consequence of metal substitution upon degree redox-site electronic coupling. From markedly (ca. 5 fold) larger intervalence band intensities, narrower bandwidths, and milder solvent dependence energy observed former system, Co(III)-Co(II) coupling is deduced be substantially greater than Fe(III)-Fe(II). A similar conclusion reached from a comparison spectra bis(fulvalene)-dicobalt -diiron monocations. These differences also reflected more negative comproportionation free energies cobalt mixed-valence analogs, as derived electrochemical data. findings consistent orbital symmetry considerations, since electron transfer system expected involve ligand-centered 4e1g orbital, strongly metal-localized 4e2 or 8a1g orbitals that apparently utilized Fe(III)-Fe(II) metallocene case. Keywords: Mixed valence compounds, Donor acceptor overlap, Electronic coupling, Biferrocene, Bicobaltocene.