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

Five new chloranilato-bridged binuclear chromium(III) complexes have been synthesized and identified as [Cr-2(CA)L-4]-(ClO4)(4) [L denotes 5-methyl-1,10-phenanthroline (Me-phen); 2,9-dimethyl-1, 10-phenanthroline (Me-2-phen); 5-chloro-1, 10-phenanthroline (Cl-phen); diaminoethane (pn) or 1,3-diaminopropane (pn)], where CA represents the dianion of chloranilic acid. Based on elemental analyses, molar conductivity and magnetic moment of room-temperature measurements, and IR and electronic spectral studies, it is proposed that these complexes have CA-bridged structures and consist of two chromium(III) ions, each in an octahedral environment. The complexes [Cr-2(CA) (Me-phen)(4)] (ClO4)(4) (1) and [Cr-2(CA) (Me-2-phen)(4)] (ClO4)(4) (2) were further characterized by variable temperature (4.2-300 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 = - 7.8 cm(-1) for (1) and J = - 6.5 cm(-1) for (2). This result indicates that there is weak antiferromagnetic spin-exchange interaction between the two chromium (III) ions within each molecule.