SYNTHESIS, CHARACTERIZATION AND MAGNETIC-PROPERTIES OF DINUCLEAR COMPLEXES OF MANGANESE(III) AND MANGANESE(II) WITH OXO AND BENZOATE DERIVATIVES AS BRIDGING LIGANDS

Four new dinuclear Mn-III complexes were synthesized: (bipy)(H2O)}(2)) (mu-O)(mu-2-ClC6H4COO)(2)](NO3)(2) (1), n(bipy)(H2O)}(2)(mu-O)(mu-3-Cl C6H4COO)(2)](NO3)(2) (2), n(bipy)(H2O)}(2)(mu-O)(mu-4-ClC6H4COO)(2)](N O3)(2) (3) and (bipy)(H2O)}(2)(mu-O)(mu-2-ClC6H4COO)(2)](ClO4)(2) (4), where bipy is 2,2'-bipyridyl and 2-, 3- and 4-ClC6H4COO are 2-, 3- an d 4- chlorobenzoate. Magnetic susceptibility measurements were carried out on this series of complexes and the data were interpreted using t he Keisenberg Hamiltonian -J(12)S(1)S(2) and led to small ferromagneti c coupling for 1 and 2 and small antiferromagnetic coupling for 3 and 4, respectively. By reaction of a solution of these complexes with H2O 2 in the presence of ClO4- anion, three new dinuclear Mn-II complexes, [{(Mn(bipy)(2)}(2) (mu-2-ClC6H4COO)(2)](ClO4)(2) (5), [{Mn(bipy)(2))( 2)(mu-3-ClC6H4COO)(2)](ClO4)(2) (6) and [{Mn(bipy)(2)}(2)(mu-4-ClC6H4C OO)(2)](ClO4)(2) (7), were obtained. Magnetic susceptibility data were interpreted with the same Hamiltonian, but for Mn-II ions instead of Mn-III. The experimental data indicate small antiferromagnetic couplin g in all three complexes. EPR spectra in powder samples and in frozen solutions agree with the formulae proposed.