Ferromagnetic interactions in metal complexes with imino nitroxides

Abstract Copper(II), nickel(II), and zinc(II) complexes with tridentate imino nitroxyl diradicals, [CuCl(bisimpy)(MeOH)](PF 6 ) ( 1 ), [NiCl(bisimpy)(H 2 O) 2 ]Cl·2H 2 O ( 2 ), and [ZnCl 2 (bisimpy)] ( 3 ) (bisimpy=2,6-bis(1′-oxyl-4′,4′,5′,5′-tetramethyl-4′,5′-dihydro-1′ H -imidazol-2′-yl)pyridine), were prepared and their magnetic properties studied. In 1–3 the diradicals are ferromagnetically coupled with the inter-radical coupling constant of J = + 6.5 cm - 1 . In 1 and 2 the ferromagnetic interactions between the paramagnetic metal ions and the coordinated imino nitroxides are operative with the J values of +165 and +120 cm −1 ( H =−2 J ij ∑ S i S j ), respectively. Magnetic properties of a Cu(II) complex with a mono radical ligand, [CuCl 2 (impy)] ( 4 ) (impy=2-(1′-oxyl-4′,4′,5′,5′-tetramethyl-4′,5′-dihydro-1′ H -imidazol-2′-yl)pyridine), were also studied; a ferromagnetic coupling constant of J = + 50 ( 2 ) cm - 1 was obtained.