A series of 1-D to 3-D metal–organic coordination architectures assembled with V-shaped bis(pyridyl)thiadiazole under co-ligand intervention

Six new coordination polymers based on V-shaped linkage 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (bpt) and transition metal ions, [Co(bpt)(pm)0.5(H2O)]n · 3nH2O (1), [Cu2(bpt)(pm)(H2O)4]n (2), [Co(bpt)(pydc)]n · 2nCHCl3 · nH2O (3), [Cu2(bpt)(pydc)2(H2O)2]n (4), [Cu2(bpt)(pydco)2(H2O)2]n · nH2O (5) and [Cd(bpt)(pydco)]n (6) (H4pm = pyromellitic acid, H2pydc = pyridine-2,6-dicarboxylic acid, H2pydco = pyridine-2,6-dicarboxylic acid N-oxide), have been synthesized under the intervention of various polycarboxylate ligands. Complex 1 exhibits a 3-D 4-connected structure with 1-D nanosized open channels encapsulated lots of water molecules. Complex 2 represents a 2-D grid containing two types of rectangular windows. When pydc and pydco instead of pm, complexes 3 and 6 were obtained with highly undulated 2-D layers. The interlayers of 3 are filled with two kinds of solvent molecules, whereas 6 is a double-layered framework without free molecules. Complexes 4 and 5 consist of two distinct 1-D infinite chains held together to form different 2-D supramolecular networks. Importantly, bpt spacer shows changeful conformational geometries and generates complicated crystalline architectures with the introduction of polycarboxylate ligands. Additionally, thermal stability of complexes 1, 3 and 5, fluorescent properties of 6 and X-ray powder diffraction of 1 have also been investigated.