Hydrothermal synthesis, structure, and porosity studies of coordination polymer [Na2(H2O)8Cu(pydc)2] n

Abstract

Synthesis and crystal structure of the title compound octaaquadisodium bis(pyridine-2,3-dicarboxylato-N,O,O)copper(II), [Na2(H2O)8Cu(pydc)2] n having a three-dimensional network, is reported (H2pydc = pyridine-2,3-dicarboxylic acid). The compound was prepared by the hydrothermal method. The crystal structure was solved by direct methods using single-crystal X-ray diffraction data collected at room temperature and refined by full-matrix least-squares procedures to a final R value of 0.0318 for 1,911 observed reflections. The compound has distorted octahedral geometry about the copper center due to Jahn–Teller distortion. The copper(II) is bonded to four symmetry-related quinolinate groups: two of them coordinate equatorially in a bidentate fashion through their nitrogen atom and one oxygen, O(1), from the 2-carboxylate group. The axial sites are provided by the other two carboxylates, through the oxygen atoms O(4) from the remaining 3-carboxylate group. Each pyridine-2,3-dicarboxylate (pydc) bridges copper(II) with sodium metal ion in a bidentate bridging mode of carboxylate group at 2-position of pydc. Each pydc also binds two different copper centers, which leads to the formation of a three-dimensional (3D) coordination polymer network. Two sodium ions are bridged through two water molecules and bonded to three more terminal water molecules. Hydrogen-bonding interaction involving water molecules and carboxylate groups strengthens the 3D network formed by the coordination polymer. The coordination polymer has a microporous structure, as is evident from the Brunauer–Emmett–Teller (BET) surface area of 5.42 m2/g. .