Synthesis, Spectral and Antiferromagnetic Interaction in Oxalato-Bridged Linear TRinuclear Oxovanadium(IV) Complexes

Three new linear trinuclear oxovanadium(IV) complexes bridged by oxalato (ox) and end-capped with 2,2_-bipyridine (bpy); 1,10-phenanthroline (phen) or 5-nitro-1,10- phenanthroline (NO2phen); respectively, namely [(VO)3(ox)2(bpy)2]SO4 (1), [(VO)3(ox)2(phen)2]SO4 (2) and [(VO)3(ox)2(NO2phen)2]SO4 (3), have been synthesized and characterized by elemental analyses, molar conductivity, magnetic measurements, IR, ESR and electronic spectral studies. It is proposed that these complexes have extended ox-bridged structures, consisting of three oxovanadium(IV) ions, each in a distorted square-pyramidal environment. Variable-temperature magnetic susceptibility measurements (4.2~300 K) of the complexes (1) and (2) revealed the occurrence of an intramolecular antiferromagnetic interaction between the oxovanadium(IV) ions through the oxalato-bridge within each molecule. The magnetic data have been also used to deduce the indicated structure. On the basis of spin Hamiltonian operator, _ _ _ H = 2J(S S S_ S_ ) 1 2 2 3 Ĺ + Ĺ , the magnetic analyses were carried out for the two trinuclear complexes and the spin-coupling constants (J) were evaluated as -9.85 cm-1 for (1) and -10.16 cm-1 for (2).