Synthesis, crystal structure, spectroscopy, and magnetism of a mixed valence Co(III)–Co(II)–Co(III) complex stabilized by <i>N</i>-(2-hydroxybenzyl)salicylaldimine

Abstract

Reaction of Co(OAc)2 · 4H2O with N-(2-hydroxybenzyl)salicylaldimine (H2La) in dimethylformamide (DMF)–H2O yields a linear trinuclear mixed valence complex [CoIII(μ-La)(μ-Lb)(μ-OAc)]2CoII · 2DMF (1). Here, HLb is salicylaldimine, which is afforded by an in situ transformation of H2La via cleavage of the C–N bond. Complex 1 has been characterized by X-ray crystallography as well as elemental analysis, UV-Vis, and IR spectroscopy. The cathodic and anodic responses of 1 in DMF appeared at −1.46 V (CoIII → CoII, quasi-irreversible) and +0.99 V (CoII → CoIII, irreversible) versus saturated calomel electrode, respectively. The magnetic behavior of 1 has been analyzed by the one-ion approximation with spin–orbit coupling in Oh symmetry giving λ = −121 cm−1.