Preparation and characterization of four polymeric metal complexes based on the flexible ligand 1H-1,2,4-triazole-1-propionic acid in different conformations

Abstract

Three 2-D layered coordination polymers with (4,4) topology, {[Cu(trzp)₂(H₂O)]·1.18H₂O} _n (1), {[Co(trzp)₂(H₂O)₂]·2H₂O} _n (2), and {[Cd(trzp)₂(H₂O)]·2H₂O} _n (3), have been synthesized with the flexible, bifunctional ligand 1H-1,2,4-triazole-1-propionate (trzp⁻) as a two-connected bridge. In addition, a complicated 3-D MOF [Ag₃(trzp)₂(NO₃)] _n (4) has been obtained with the help of Ag⋯Ag interactions and trzp⁻ as a four-connected linker. Htrzp and 1–4 have been characterized by single-crystal X-ray diffraction, elemental analysis, and infrared spectroscopy. The structural analysis showed that Htrzp has a gauche conformation in the solid state. However, both gauche and trans conformers of trzp⁻ are observed in the crystals of 1; only one conformer of trzp⁻ exists in the other three compounds (trans conformation in 2 and 3, and gauche conformation in 4). The thermal behaviors of 1–4 have been examined by thermal gravimetric analysis under nitrogen, which revealed that metal cyanide salts M(CN) _n (M = Cu(II), Co(II), Cd(II), and Ag(I), n = 1 or 2) may be an intermediate pyrolytic decomposition product of the corresponding compounds.

Keywords:

• Preparation
• Crystal structure
• 1H-1,2,4-Triazole-1-propionic acid
• Conformational flexibility

Acknowledgements

This work was financially supported by the Guangxi Natural Science Foundation of China (grant no. 2010GXNSFF013001, 0832023) and Scientific Research Foundation of Guangxi Normal University.