Spin coupling interactions in transition metal complexes containing radical o-semiquinone ligands. A review

Transition metal complexes of o-semiquinone (SQ) ligands have been studied extensively over the past 25 years. A particularly interesting aspect of th is coordination chemistry concerns magnetic interactions between paramagnet ic metal ions and the radical anionic ligands. In this review we begin with a survey of relatively simple complexes consisting of a paramagnetic metal ion chelated by a single SQ ligand. Recent studies have revealed the impor tance of SQ-SQ coupling through diamagnetic metals, and complexes of this c lass are described in the second section of the review. Both interactions c ombine to account for the often complicated magnetic properties of complexe s containing multiple SQ ligands chelated to a paramagnetic metal ion. Rese arch on these complexes is surveyed in the third section with a concluding look toward polymeric SQ complexes. A review with 51 references.