Structures and Properties of Two New Three-Dimensional Inorganic-Organic Hybrid Compounds Based on Isopolymolybdate Clusters

Two new inorganic-organic hybrid materials containing different isopolymolybdate units, namely, [Ce(pdca)(H2O)}{Ce(pdca)(H2O)(5)}](2){Mo8O26}center dot 10H(2)O (1), [Cu(phen)(H2O)(2)](2)[Mo6O20] (2) (pdca=pyridine-2,6-dicarboxylic acid, phen=1,10-phenanthroline) have been successfully synthesized under hydrothermal conditions, and characterized by elemental analyses, IR spectra, thermal gravimetric analyses (TGA), single-crystal X-ray diffraction and powder X-ray diffraction (PXRD). In compound 1, Ce(III) ions are bridged by pdca ligands to form cerium-organic coordination layers, which are further pillared by octamolybdate clusters via the covalent bonding of Ce-O, leading to the formation of a 3D pillar-layered open-framework architecture. Compound 2 features a 3D supramolecular structure constructed by hydrogen bond interactions between 1D molybdate chains aggregated by [Mo6O20](4-) polyoxoanions and coordinated water molecules. It was remarkable that H-3[PMo12O40]center dot H2O decomposes into hexamolybdate anions, which are linked together with phen ligands by Cu(II) cation. Moreover, UV-vis spectra and fluorescence properties of compounds 1-2 have also been investigated in detail.