Synthesis and magnetic studies of phthalato-bridged oxovanadium(IV) binuclear complexes

Six new mu-phthalato binuclear oxovanadium(IV) complexes, namely [(VO)(2)(PHTH)(L)(2)]SO4 (L denotes 2,2'-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4'-dimethyl-2,2'-bipyridine (Me(2)bpy); 5-nitro-1,10-phenanthroline (NO2-phen); 5-chloro-1,10-phenanthroline (Cl-phen) and 5-methyl-1,10-phenanthroline (CH3-phen), where PHTH is the phthalate dianion), have been synthesized and characterized by elemental analyses, IR, electronic spectra, magnetic moments at room temperature and molar conductivity measurements. The temperature dependence of the magnetic susceptibility of complexes [(VO)(2)(PHTH)(phen)(2)]SO4 (1) and [(VO)(2)(PHTH)(CH3-phen)(2)]SO4 (2) was measured in 4-300 K range and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, (H) over cap=-2J (S) over cap(1) .($) over cap(2), giving the exchange integrals J=-12.8 cm(-1) for 1 and J=-7.9 cm(-1) for 2. This indicates an antiferromagnetic spin-exchange interaction between the metal ions within each molecule.