Halogeno(triazolyl)zinc complexes as molecular building blocks for metal-organic frameworks

The isomorphous title complexes, dichlorido[4-(3,5-dimethyl-4H-1,2,4-triazol-4-yl) benzoic acid-kappa N(1)]zinc(II) dihydrate, [ZnCl(2)(C(11)H(11)N(3)O(2))(2)]center dot 2H(2)O, and dibromido[4-(3,5-dimethyl-4H-1,2,4- triazol-4-yl) benzoic acid-kappa N(1)]zinc(II) dihydrate, [ZnBr(2)(C(11)H(11)N(3)O(2))(2)]center dot 2H(2)O, were synthesized and crystallized by slow evaporation of the solvent from a solution of the ligand and either zinc chloride or zinc bromide, respectively, in water/ethanol. The Zn(II) ions occupy twofold axes in the noncentrosymmetric orthorhombic space group Fdd2. The metal ion is approximately tetrahedrally coordinated by two monodentate triazole groups of the ligands and additionally by two halide ions. The water molecules incorporate the complexes into a three-dimensional framework made up by hydrogen bonds. Furthermore, each complex possesses two hydrogen-bond-donor sites represented by the carboxy groups and two acceptor sites at the noncoordinating N atoms of the triazoles.