One dimensional coordination polymers of Cd(II) and Zn(II): Synthesis, structure, polar packing through strong inter-chain hydrogen bonding and gas adsorption studies

Abstract

Two one dimensional coordination polymers of Cd(II) and Zn(II), {[Cd(NPBI)(BDC)(H2O)]·2H2O}n (1) and {[Zn(NPBI)(BDC)]·H2O}n (2), [NPBI = 1,1′-(4-nitro-1,3-phenylene)bis(1H-benzo[d]imidazole), BDC = 1,3-benzenedicarboxylate] have been synthesized under solvothermal conditions. Both compounds have been characterized by single X-ray crystallography, IR spectroscopy, TGA and elemental analysis. These one dimensional (1D) structures are further stacked to three dimensional (3D) supramolecular framework through polar packing which arises through intensive hydrogen bonding interactions giving rise to 1D dumbbell shaped small cavities which accommodate lattice water molecules. After removal of solvent molecules, permanent porosity in complex 1 with 13.6% void volume was verified by CO2 sorption isotherm that shows selective CO2 gas uptake at low temperature (195 K) as well as at ambient temperature conditions (273 K and 298 K). Topological analysis shows that coordination polymer 1 possesses uninodal 4-connected SP1-periodic net with point symbol {33.42.5} and compound 2 assumes 3-connected SP1-periodic net with point symbol {42.6}.