An isomer of a POM-based hybrid compound formed through different linkage between CuI ions and pyrazine

One 3D Keggin polyoxometalates-based hybrid compound, [Cu4(pz)6(H2O)2(SiW12O40)] (1) (pz = pyrazine), was hydrothermally synthesized and characterized by an elemental analysis, IR spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. In compound 1, [Cu4(pz)6(H2O)2] n 4n+ polymeric cation has 2D network structure including ten-metal rings. The two 2D networks are linked through sharing a coordination water into a double-layer structure. [SiW12O40]4− anions are embedded between two double-layers through the coordination of Ot atoms to Cu atoms. The pyrazine molecule is in situ formed from the decarboxylation of pyrazine-2,3-dicarboxylic acid. The IR data of 1 also proved the correctness of the structure due to no characteristic peak of carbonyl group in IR spectrum. Thermogravimetric analysis and fluorescence of 1 are also analyzed and discussed.