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)]center dot 1.5H(2)O}(n) (1) and [Co(bpdc)(Hpb)(H2O)](n) (2) (bpdap = N,N'-bis(2-pyridyl)-2,6-diaminopyridine, H(2)bpdc = 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 P (1) over bar. 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 pi-pi 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 center dot center dot center dot pi interactions. Magnetic measurement reveals that both 1 and 2 present weakly antiferromagnetic behavior.