Mn(II) ion centers in novel coordination environment: a new two-dimensional coordination polymer [Mn(3,5-pdc)·2H2O]

The hydrothermal synthesis and structure of the coordination polymer Mn(3,5-pdc)·2H₂O] (3,5-pdc=3,5-pyridinedicarboxylic acid) with a novel seven-coordination mode of Mn(II) ion is reported. The metal ion center is in the pentagonal bipyramid coordination environment. Oxygen atoms from two waters hold the axial sites, and four oxygen atoms from two chelated carboxylic groups and one nitrogen atom from one pyridine ring occupy the five planar sites. This novel coordination environment of Mn(II) ion may be due to the smaller steric effect of chelated carboxylic groups. Each 3,5-pdc ligand is in the same coordination mode to bridge three Mn(II) ion centers and lead to two-dimensional layers with water molecules between the layers. Hydrogen bonds, which are generated by these water molecules and carboxylic groups, connect the layers to form a three-dimensional structure.