Synthesis, structures and magnetic properties of two 3D 3,4-pyridinedicarboxylate bridged manganese(II) coordination polymers incorporating 1D helical Mn(carboxylate)(2) chain or Mn-3(OH)(2) chain

摘要

The hydrothermal reactions of MnCl2• 4H(2)O, 3,4-pyridinedicarboxylic acid (3,4-pydaH(2)) and triethylamine in aqueous medium yield two 3D metal-organic hybrid materials, [Mn(3,4-pyda)] (1) and [Mn-3(OH)(2)(3,4-pyda)(2)(H2O)(2)] (2), respectively. In both complexes, each 3,4-pyda acts as a pentadentate ligand to connect five Mn(II) atoms via the pyridyl group and the two μ(2)-carboxylate groups (one in syn,anti-mode and one in syn-syn mode for 1 and both in syn,anti-mode for 2). Complex 1 possesses an interesting 3D coordination polymeric structure incorporating 1D helical Mn(μ(2)-carboxylate)(2) chain units, in which each Mn(II) atom is coordinated in less common square pyramidal geometry to four carboxylato oxygen atoms and one pyridyl nitrogen atom. Each 3,4-pyda links three helical Mn(μ(2)-carboxylate)(2) chains and each Mn(μ(2)-carboxylate)(2) chain is linked by other eight helical Mn(μ(2)-carboxylate)(2) chains via sharing 3,4-pyda bridges. Complex 2 is a 3D coordination network consisting of ID Mn-3(OH)(2) chains and 3,4-pyda bridges. The repeating trimeric structural unit in the manganese(II) hydroxide chain consists of two edge-sharing symmetry-related manganese octahedra linked via μ(3)-OH to a vertex of Mn-2 octahedron. Each 3,4-pyda links three Mn-3(OH)(2) chains and each Mn-3(OH)(2) chain is linked by other six Mn-3(OH)(2) chains via 3,4-pyda bridges, resulting in a 3D coordination solid. Magnetic measurements reveal that a weak antiferromagnetic interaction between the Mu(II) ions occurs in complex 1 and a 3D magnetic ordering at about 7.0 K in complex 2. © 2005 Elsevier Inc. All rights reserved.