Experimental and theoretical studies on ferromagnetically coupled metal complexes with imino nitroxides

Copper(II), zinc(II), and nickel(II) complexes with tridentate imino nitrox yl diradicals, [CuCl(bisimpy)(MeOH)]-(PF6) (1), [ZnCl2(bisimpy)] (2), and [ NiCl(bisimpy)(H2O)(2)]Cl . 2H(2)O (3) (bisimpy = 2,6-bis(1'-oxyl-4',4',5',5 '-tetramethyl-4',5'-dihydro-1'H-imidazol-2'-yl)pyridine), were prepared, an d their magnetic properties were studied. In 1, the Cu(II) ion has a square pyramidal coordination geometry, of which the equatorial coordination site s are occupied by three nitrogen atoms from the bisimpy and a chloride ion. The coordination geometry of the Zn(II) ion in 2 can be described as a tri gonal bipyramid, with two chloride ions and a bisimpy. In 3, the Ni(II) ion has a distorted octahedral coordination geometry, of which four coordinati on sites are coordinated by the bisimpy and chloride ion, and two water mol ecules occupy the remaining cis positions. Magnetic susceptibility and EPR measurements revealed that in 1 and 3 the Cu(II) and Ni(II) ions with imino nitroxyl diraicals were ferromagnetically respectively, and the coupled, w ith the coupling constants J (H = -2J(ij)SigmaS(i)S(j)) of +165(1) and 109( 2) cm(-1), intraligand ferromagnetic interactions in 1-3 were very weak. DF T molecular orbital calculations were performed on the diradical ligand, 1, and 2 to study the spin density distribution before and after coordination to the metal ions.