Effect of pH on the construction of zinc coordination polymers based on carboxylate functionalized triazole derivative ligand

Abstract

Two new coordination polymers, namely, [Zn2(L)2(H2O)4]n·nH2O (1) and [Zn2(L)2(H2O)2]n·nH2O (2) (H2L = 5-(1H-1,2,4-triazol-1-yl)-1,3-benzenedicarboxylic acid), were constructed by changing pH under hydrothermal condition and characterized by elemental analysis, IR and single crystal X-ray diffraction. Compound 1 is formed at pH 3.5, which displays a 3-connected two-dimensional (2D) layer structure with the Schläfli symbol of 63 and are further extended into a three-dimensional (3D) supramolecular network by inter-molecular hydrogen bonds and π … π stacking interactions. While at pH 5.5, compound 2 displays a unusual 3D coordination network which exhibits an intriguing self-interpenetrating (3,6)-connected topological net with the Schläfli symbol of (4.62)2(42.69.83.10). Interestingly, Compounds 1 and 2 were obtained in the similar reaction conditions. The structural differences of two compounds give some insights into the effect of pH on the construction of coordination polymers. Additionally, the thermal stabilities and photoluminescence properties of 1 and 2 were also studied.