Cobalt(III) Bis-o-semiquinone Complexes with p-Tolyl-Substituted Formazan Ligands: Synthesis, Structure, and Magnetic Properties

New heteroligand cobalt(III) bis-3,6-di- tert -butyl- o -benzosemiquinone complexes with p- tolyl-substituted formazan ligands Co(3,6-SQ) 2 L n (L 1 H is 1,5-diphenyl-3- p -tolylformazan ( I ), L 2 H is 1,3,5-tri- p -tolylformazan ( II ), and L 3 H is 3-nitro-1,5-di- p -tolylformazan ( III )) are synthesized and characterized. The molecular structures of compounds I , II , and III in the crystalline state are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 2161722 ( I ), 2167094 ( II ), and 2167095 ( III )). According to the XRD results and magnetic and spectral measurement data, compounds I – III are complexes of low-spin cobalt(III) bound to two radical anion o- semiquinone ligands and one formazan anion. The magnetic behavior of the complexes in a temperature range of 2–300 K is characterized by intramolecular antiferromagnetic exchange interactions between the o- semiquinone ligands. The replacement of the phenyl substituents by p- tolyl groups in positions 1 and 5 of the diamagnetic formazanate ligand results in a significant enhancement of the exchange between the radical centers.