Synthesis, structure and magnetic properties of the first two-dimensional infinite sheet-like mixed-valence manganese(II,III) complex with bridging salicylate and pyridine-2-carboxylate ligands
Abstract
A two-dimensional infinite sheet-like mixed-valence manganese(II,III) complex [{Na2Mn4(sal)4(pyca)4-(MeOH)2}n]·2nH2O (H2sal = salicyclic acid and Hpyca = pyridine-2-carboxylic acid) has been prepared and characterized by X-ray crystallography and magnetic measurements. The structure consists of a [Mn4(sal)4(pyca)4(MeOH)2]n2n– anion, 2nNa+ cations and 2n non-coordinated H2O. In every [Mn4(sal)4(pyca)4(MeOH)2]2– unit there are two six-co-ordinate MnIII[Mn(1) and Mn(2)] located at symmetry centres, and two six-co-ordinate MnII[Mn(3) and Mn(3′)]. Atoms Mn(1) and Mn(3)[or Mn(2) and Mn(3)] are connected by a salicylate (pyridine carboxylate) carboxylate in a syn-anti configuration, while Mn(3) and Mn(3′) are bridged by two oxygen atoms of two pyridine carboxylates. The Na+ cation is six-co-ordinated, having contacts with six oxygens of carboxylate groups of Mn(1), Mn(2) and Mn(3) polyhedral units. The magnetic behaviour of the complex in the temperature range 1.4–300 K has been interpreted in terms of a dimer unit [MnII2(pyca)2] and two manganese(III) polyhedral units assuming the MnIII to obey a Curie–Weiss law, and the values obtained for J, g and θ were –0.98 cm–1, 2.00 and –5.66 K (–3.93 cm–1), respectively.