Crystal structures and thermal decomposition kinetics of three new Zn(II) coordination polymers based on 3-amino-1,2,4-triazole

Abstract

Solvothermal reactions of Zn(NO3)2·6H2O, 3-amino-1,2,4-triazole as well as three different carboxylate ligands afforded three novel coordination polymers: [Zn2 (azdc) (atz) (OH) (H2O)]n (1), {[Zn1.5 (btc)0.5 (atz)]·1.5H2O}n (2), and {[Zn4 (nipa)2 (atz)3(OH) (H2O)]·2H2O}n (3) (H2azdc = 4,4′-azobenzoic acid, H4btc = 1,2,4,5-benzenetetracarboxylic acid, 5-H2nipa = 5-nitroisophthalic acid, Hatz = 3-amino-1,2,4-triazole). Moreover, the three coordination polymers have been characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, and powder X-ray diffraction techniques. Complex 1 reveals a 2D layer structure, which is further connected through π–π stacking interactions forming a 3D supramolecular network. Complex 2 exhibits a 3D porous framework with 1D open channels. Complex 3 shows a 3D pillared-layer framework. Notably, the thermal decomposition processes of 1–3 were investigated by simultaneous TG−DSC techniques. The TG curves reveal that complexes 1–3 possess pretty good thermostability up to 321 °C, 416 °C and 418 °C, respectively. The apparent activation energy E (E1 = 194.975 kJ mol−1, E2 = 220.360 kJ mol−1, E3 = 223.600 kJ mol−1) and the pre-exponential factor A of skeleton collapse for the complexes 1–3 were calculated by the integral Kissinger's method and Ozawa−Doyle's method. The structural stability could be illustrated from the point of thermal decomposition kinetics.