Synthesis, crystal structure and characterization of a three‐dimensional Cd II II coordination polymer constructed from 2,5‐bis(1 H H ‐1,2,4‐triazol‐1‐yl)terephthalate

摘要

Bifunctional organic ligands are very popular for the design of coordination polymers because they allow the formation of a great diversity of structures. In the title coordination polymer, the new bifunctional inversion‐symmetric ligand 2,5‐bis(1 H ‐1,2,4‐triazol‐1‐yl)terephthalic acid (abbreviated as H 2 bttpa) links Cd II cations, giving rise to the three‐dimensional Cd II coordination polymer catena ‐poly[diaqua[μ 4 ‐2,5‐bis(1 H ‐1,2,4‐triazol‐1‐yl)terephthalato‐κ 4 O 1 : O 4 : N 4 : N 4′ ]cadmium(II)], [Cd(C 12 H 6 N 6 O 4 )(H 2 O) 2 ] n or [Cd(bttpa)(H 2 O) 2 ] n . The asymmetric unit consists of half a Cd II cation, half a bttpa 2? ligand and one coordinated water molecule. The Cd II cation is located on a twofold axis and is hexacoordinated in a distorted octahedral environment of four O and two N atoms. Four different bttpa 2? ligands contribute to this coordination, with two carboxylate O atoms in trans positions and two triazole N atoms in cis positions. Two aqua ligands in cis positions complete the coordination sphere. The fully deprotonated bttpa 2? ligand sits about a crystallographic centre of inversion and links two Cd II cations to form a chain in a μ 2 ‐terephthalato‐κ 2 O 1 : O 4 bridge. This chain extends in the other two directions via the triazole heterocycles, producing a three‐dimensional framework. O—H…O hydrogen bonds and weak C—H…N interactions stabilize the three‐dimensional crystal structure. The FT–IR spectrum, X‐ray powder pattern, thermogravimetric behaviour and solid‐state photoluminescence of the title polymer have been investigated. The photoluminescence is enhanced and red‐shifted with respect to the uncoordinated ligand.