From Hydrogen-Bonded Net-to-Net Framework to Twofold Interpenetrated (4,6) Net: Effect of Ligand Topology on the Supramolecular Structural Diversity

Two novel metal−organic frameworks (MOFs) of Co(II), {[Co(bpdc)(bpdap)]·1.5H2O}n (1) and [Co(bpdc)(Hpb)(H2O)]n (2) (bpdap = N,N‘-bis(2-pyridyl)-2,6-diaminopyridine, H2bpdc = biphenyl-4,4‘-dicarboxylic acid, and Hpb = 2-(2-pyridyl)-benzimidazole), have been synthesized by a hydrothermal method and structurally characterized. The structure determination reveals that both 1 and 2 crystallize in a triclinic system, space group P1̄. Complex 1 has a 1D zigzag chain where Co(II) is bridged by bpdc in alternate bis(monodentate) and bis(chelate) manners and extends to form a 2D rectangular grid (RG) framework stacking in a staggered manner through hydrogen bonding and π−π interactions to form a net-to-net supramolecular network with a small channel along the c-axis, which accommodates the water molecules. In the case of 2, a zigzag chain with Co(II) connected by bis(monodentate) bpdc results in a 2D RG network based on hydrogen bonding, and every two networks interlock slantwise forming a twofold interpenetrated (4,6) net framework that is stabilized by C−H···π interactions. Magnetic measurement reveals that both 1 and 2 present weakly antiferromagnetic behavior.