Three open-framework coordination polymers with new topological structures built on two tripod ligands

By using flexible tricarboxylate 4,4′,4″-(((2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene))tris(oxy))tribenzoic acid (H3L) and multiimidazole 1,3,5-tri(imidazo-1-ylmethyl)-2,4,6-trimethylbenzene (titb) ligands simultaneously, three novel coordination polymers [M3L2(titb)2]·2H2O·2.5DMF (M = Co,1; Zn, 2; Cd, 3) were synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction, thermogravimetric and photoluminescent studies. The three compounds are isomorphous and possess a three-dimensional (3D) framework built from 2D sheets of L3− ligands and M ions, and 1D chains of titb ligands and M ions. Topological analyses showed that they exhibit a novel (3,3,4,4) four-nodal 3D net constructed from two 4-connecting metal, and two 3-connecting L3− and titb nodes. Compounds 2 and 3 are photoluminescent upon excitation at room temperature.