Synthesis, structure and magnetic properties of a singly carboxylate-bridged dinuclear manganese(II) complex

A novel dinuclear manganese(ii); complex bridged by a single carboxylate ligand [{(Mn(bipy)(2)(H2O)}(2)(Me3NCH2CO2)] [ClO4](4) . 2H(2)O (bipy = 2,2'-bipyridine) has been prepared and structurally characterized by X-ray crystallography. It crystallizes in the monoclinic space group C2, with a = 16.321(5), b = 13.354(5), c = 13.298(2) Angstrom, beta = 96.55(2)degrees. Refinement converged to R = 0.066 for 1975 observed reflections with l greater than or equal to 2 sigma(l). The crystal structure comprises a dinuclear cation, perchlorate anions and lattice water molecules. The pair of metal ions separated at 5.67 Angstrom in the cation is bridged by a single syn-anti carboxylate ligand. Each metal ion is co-ordinated in a distorted octahedral N4O2 geometry by two chelate bipy ligands [Mn-N 2.238(8)-2.257(7) Angstrom], one aqua ligand 12.173(7) Angstrom] and one mu-carboxylate oxygen atom [Mn-O = 2.081(10), 2.193(10) Angstrom]. The powder EPR spectrum at 77 K shows a broad absorption at g = 1.970. The temperature-dependent magnetic susceptibility data (4:4-95.0 K) were fitted:based on H = -2JS(1) . S-2, yielding the intramolecular coupling constant J value of -0.193 cm(-1).