Synthesis, characterization and magnetism of chloranilato-bridged chromium(III)-chromium(III) binuclear complexes

Four new chloranilato-bridged chromium(III)-chromium(III) binuclear complexes of the formula [Cr-2(CA)L-4](SO4)(2) [L denotes 2,2'-bipyridine (bpy); 1,10-phenanthroline (phen); 5-nitro-1,10-phenanthroline (NO2-phen) and 5-bromo-1,10-phenanthroline (Br-phen), respectively], where CA represents the dianion of chloranilic acid, have been synthesized and characterized. Based on elemental analyses, molar conductivity and magnetic moment of room-temperature measurements and spectroscopic studies, it is proposed that these complexes have CA-bridged structures and consist of two chromium(III) ions, each in a distorted octahedral environment. The complexes [Cr-2(CA)(phen)(4)](SO4)(2) (1) and [Cr-2(CA)(bpy)(4)](SO4)(2) (2) were further characterized by variable temperature (4 similar to 300 K) magnetic susceptibility measurements and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, (H) over cap = 2J (S) over cap(1) . (S) over cap(2), giving the exchange parameter J = -8.9 cm(-1) for (1) and J = -6.6 cm(-1) for (2). This result indicates that there is a weak antiferromagnetic spin-exchange interaction between the two chromium(III) ions within each molecule.