Structure and magnetic properties of a cobalt(III) complex with redox-active 1-(2-pyridylazo)-2-phenanthrol (papl)

We report the structural and variable temperature magnetic properties of a cobalt complex with the redox active ligand 1-(2-pyridylazo)-2-phenanthrol (papl). We observe production of an ionic complex consisting of cobalt(III) coordinated to two papl anions, with charge balance provided by a tetrahedral complex of cobalt(II) containing chlorides and THF solvent. The electronic spectra of this complex differs from that observed from other M(papl)2 complexes as a result of contributions from ligand-to-metal charge transfer (LMCT) states, not observed in the spectra of other reported divalent metal complexes. Variable temperature magnetic susceptibility data is typical for a tetrahedrally coordinated cobalt(II) ion with contributions from orbitally degenerate excited states and zero-field splitting. This study represents the first structurally characterized metal complex of papl with a trivalent metal ion. We also investigate the electronic and magnetic properties of the complex and support our results with density functional theory calculations.