Magneto-structural studies of a one dimensional Mn(II) coordination polymer derived from a flexible polydentate ligand

Abstract

The polydentate ligand LHμ contains bipyridine, hydrazone and oxime functionalities and reacts with Mn(CH3COO)2·4H2O to afford an alternating one dimensional chain comprising Mn(II) ions, [{Mn2(LH)(CH3COO)3(CH3OH)2}·CH3OH]n(1). The structure of 1 contains two Mn(II) ions in the asymmetric unit; Mn1 adopts an unusual pentagonal bipyramidal coordination geometry comprising an [N3O4] donor set, while Mn2 adopts a more conventional octahedral geometry coordinated by an [NO5] donor set. The two manganese ions within the dinuclear unit are connected to each either via Ohydrazone and syn-syn Oacetate bridges. These dinuclear units are then linked by anti-anti Oacetate bridges, affording a magnetic 1-D alternating chain topology. Magnetic studies on 1 reveal the presence of weak antiferromagnetic interactions via Ohydrazone and acetate bridges. The magnetism of 1 was modelled using a dimer model [Ĥ = −2JŜ1Ŝ2], with inter-dimer exchange modelled using a mean field term (zJ’) to afford g = 2.046 ± 0.002, J/k = -1.03 ± 0.02 cm−1 and zJ’ = −0.06 ± 0.01 cm−1.