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

Four new chloranilato-bridged chromium(III)-chromium(III) binuclear complex es 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-bro mo-1,10-phenanthroline (Br-phen), respectively], where CA represents the di anion of chloranilic acid, have been synthesized and characterized. Based o n elemental analyses, molar conductivity and magnetic moment of room-temper ature measurements and spectroscopic studies, it is proposed that these com plexes have CA-bridged structures and consist of two chromium(III) ions, ea ch 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 measur ements and the observed data were successfully simulated by the equation ba sed 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 antiferr omagnetic spin-exchange interaction between the two chromium(III) ions with in each molecule.