Synthesis and structural determination of four novel metal-organic frameworks in a Zn-3-amino-1,2,4-triazole system

Four new coordination polymer compounds have been prepared using 3-amino-1,2,4-triazole (AmTRZ) as an organic linker, namely, ZnCl(AmTRZ) (1), Zn(HCO(2))(AmTRZ) (2), Zn(5)(OH)(2)(AmTRZ)(6)(NO(3))(2)center dot 6H(2)O (3), and Zn(5)(OH)(AmTRZH)(AmTRZ)(6)(HCO(2))(3)center dot 5H(2)O (4). They were synthesized under mild hydro- or solvothermal conditions using water or dimethylformamide as solvent. Their crystal structures were characterized by single-crystal X-ray diffraction techniques, and thermal properties of all compounds were examined by thermogravimetric analysis. Isostructural compounds 1 and 2 (Pbca, a = 9.389(1) angstrom, b = 10.115(1) A, c = 11.571(2) A, V = 1098.9(3) angstrom(3), Z = 8 for 1 and a = 9.198(1) angstrom, b = 10.341(1) angstrom, c = 12.577(2) angstrom, V = 1196.2(3) angstrom, Z = 8 for 2) display a two-dimensional layer structure where Zn centers are linked by AmTRZ molecules to form gridlike layers containing eight-membered rings. Structure 3 (Pa (3) over bar, a = 15.0448(6) angstrom, V = 3405.3(2) angstrom(3), Z = 4) is a dense three-dimensional framework, featuring seven-membered channels where water and nitrate anions are located. Structure 4 (I4/m, a = 19.2576(9) angstrom, c = 20.286(2) angstrom, V = 7523.2(9) angstrom(3), Z = 8) is built from porous Zn-AmTRZ layers containing 12- and 8-membered rings, which are connected to each other by dinuclear Zn tetrahedra building units. Water and formate anions occupy the void inside the framework.