Phbtoinduced Valence Tautomerism in Cobalt Complexes Containing Semiquinone Anion as Ligand: Dynamics of the High-Spin [Co~(II)(3,5-dtbsq)_2] to Low-Spin [Co~(III)(3,5-dtbsq)(3,5-dtbcat)j Interconversion

摘要

Cobalt complexes with two semiquin one-derived ligands have been shown to undergo a valence tautoraeric inter-conversion between high-spin [Co~(II)N N)(sq)_2] and low-spin [Co~(III)(N N)(sq)(cat)] forms, where N N is a chelating diiminium ligand suchas 2,2'-bipyridine (bpy). In these molecules, an intramolecular electron transfer converts the high-spin Co~(II) ion to a low-spin Co~(III) ion, and one of the ligands is reduced by one electron from a semiquinone anion ligand (sq~-) to acatecholato (cat~(2-)) ligand There are two different mixed-valence isorners of the Co~(III) complex. The dynamical processes that are possible for such a valence-tautomeric complex are summarized in Scheme 1.