N-donor co-ligand-driven zinc coordination polymers based upon a bithiophene dicarboxylate: syntheses, structures, and luminescent properties

Three zinc compounds assembled from a bithiophene dicarboxylic acid (H₂DMTDC) and different N-donor co-ligands, [Zn(DMTDC)(bpt)(H₂O)]_n (1), {[Zn(DMTDC)(5,5-dmbpy)]·0.5DMF·1.5H₂O}_n (2), and {[Zn(DMTDC)(1,3-bimb)]·2DMF·H₂O}_n (3) (H₂DMTDC = 3,4-dimethylthieno[2,3-b]thiophene-2,5-dicarboxylic acid, bpt = 4-amino-3,5-bis(4-pyridyl)1,2,4-triazole, 5,5′-dmbpy = 5,5′-dimethyl-2,2′-bipyridyl, 1,3-bimb = 1,3-bis(imidazol-1ylmethyl)benzene), were solvothermally synthesized and characterized. Compounds 1 and 2 are 1-D linear and zigzag chains with different supramolecular structures. In 1, adjacent chains form zipper-like structures through N–H⋯N interactions. In 2, however, chains in adjacent layers are stacked in an unusual unparallel level through C–H⋯O interactions. Compound 3 features a highly corrugated 2-D (4,4) layer and the layers are penetrated by each other to give 3-D polycatenations. Right- and left-handed helical Zn-bimb chains are arranged alternately within and between the layers, leading to mesomeric property of the whole network. Thermal stability and the decomposed products of all compounds were investigated. Luminescent properties of the ligands and compounds in the solid state at room temperature have also been explored. Moreover, the luminescence intensities of the compounds in different solvents are largely dependent on the solvent.