Hydrothermal Syntheses And Characterization Of Organic-Molybdate Hybrid Materials

Combining the merits of organic materials and inorganic materials, organic-inorganic hybrid materials have diverse potential applications. In such materials, the inorganic oxide contributes to the increased complexity and hence functionality through incorporation as one component in a multilevel-structured material where there is a synergistic interaction between the organic and inorganic components. As a subclass of the hybrid materials, organic-molybdate hybrid materials are of great importance. They are enjoying widespread interests due to their potential applications in catalysis, medicine, electron conductivity, magnetism and photochemistry as well as their interesting structure features. In this paper, we have hydrothermally prepared eight organic-molybdate hybrid materials associated with organic amines or their transition metal coordination groups. They have been characterized by elemental analysis, single crystal X-ray diffraction, IR, thermal analysis, UV-Vis DRS. These eight compounds are [M(en)₃]MoO₄ (en = ethylenediamine) (M= Cd, 1; Zn, 2; Ni, 3), (H₂en-Me)Mo₃O₁₀ (enMe = 1,2-propanediamine) (4), (H₂pn)Mo₃O₁₀·2H₂0 (pn = 1,3-propanediamine) (5), (H₂tren)₂[Mo₅O₁₅(HPO₄)₂]·4H₂O (tren = diethylenetriamine) (6), (Htren)₂{Ni[Mo₆O₁₂-(OH)₃(H₂PO₄)₃(HPO₄)]₂}·2tren·8H₂O (7), (H₂tren)₂(HamImi)₂[Co₃Mo₁₂O₂₄(OH)₆(HPO₄)₆-(PO₄)₂]₂·5.26H₂O (amImi = 1-(2-aminoethyl)-2-methyl-2-Imidazoline) (8)。The synthesis experiments indicated that the products were complicatedly affected by the employed hydrothermal conditions such as the systematic pH, temperature and the ratio of starting materials. Compounds 1, 2 and 3 are isostructural, in which the metal-ligand subunits M(en)3²⁺ serve as isolated coordination cations. The double chains in compounds 4 and 5 are built up from edge-shared MoO₆ octahedra, while propanediamine cations are located between the one-dimensional chains. The Strandberg type anions in compound 6 are isolated and interacted with the organic substrates through hydrogen bonds. Both compounds 7 and 8 contain Mo₆P₄ clusters. In compound 7, two Mo₆P₄ units are connected by octahedral Ni²⁺ to form a sandwich-shaped cluster. In compound 8, each two Mo₆P₄ units are connected by octahedral Co²⁺ into a sandwich-shaped cluster, the sandwich-shaped clusters are then linked by tetrahedrally-coordinated cobalt into two-dimensional layers. Owing to the hydrogen bonds, compounds 1-8 all form the extended three-dimensional supramolecular network.