Molecular self-assembly of cadmium-triazolate complexes via hydrogen bonding: Synthesis, structures and photoluminescent properties

Two new cadmium coordination polymers namely [Cd(HAmTrz–COO)4(NH4+)2] 1; and [Cd(HAmTrz)2I2]n 2; (HAmTrz–COOH = 3-amino-1,2,4-triazole-5-carboxylic acid), have been prepared based on HAmTrz–COOH as ligand. The crystal structures of 1 and 2 have been determined by single-crystal X-ray diffraction technique. In coordination-complex 1 four triazole ligands coordinate via N1 nitrogen leading to a tetrahedral geometry around cadmium ion, while in 2 the ligand prefers to coordinate to the metal in a bidentate bridging mode. The structures of both the coordination polymers can be envisaged as 3D hydrogen bonded networks. Thermogravimetric analysis shows that 2 is more stable than 1 owing to different coordination numbers of cadmium atoms. Photoluminescence properties of both the compounds have been investigated in the solid state.

Graphical AbstractThe synthesis of two new cadmium coordination polymers namely [Cd(HAmTrz–COO)4(NH4+)2] 1; and [Cd(HAmTrz)2I2]n2; (HAmTrz–COOH = 3-amino-1,2,4-triazole-5-carboxylic acid) have been accomplished via variations in the reaction conditions. Both the compounds self-assemble into 3D hydrogen bonded networks assisted by supramolecular synthons. Thermal and photoluminescence properties have been examined in the solid state.Figure optionsDownload as PowerPoint slideResearch Highlights
► In both the polymeric structures, hydrogen bonds working in cooperativity with covalent interactions are capable of ‘maneuvering’ complex ions into desirable motifs.
► These are one of a few d10 transition metal coordination polymers where phenomenon of cooperativity of hydrogen bonding is very prominently manifested in the robustness of the overall framework structures.