Four high-dimensional compounds constructed from V-shaped multidentate organic ligands and octamolybdates: Syntheses, crystal structures and properties

By using a V-shaped multidentate N-donor ligand, four new octamolybdate-based inorganic-organic hybrids, formulated as [Cu4(H3X)4(H2O)2(β-Mo8O26)2]·7H2O (1), [Cu2(H2X)(β-Mo8O26)0.5]·H2O (2), [Co(H3X)2(H4Mo8O28)] (3) and [Ni(H3X)2(H4Mo8O28)] (4) (H2X = 2,6-dimethyl-3,5-bis(pyrazol-3-yl)pyridine), have been synthesized successfully under hydrothermal conditions and characterized by single crystal X-ray diffraction analyses, elemental analyses and IR spectra. Compounds 1 and 2 with helical chains exhibit three-dimensional (3D) frameworks with (3,4)-connected {83}2{85;10} and (3,4,6)-connected {4;62}2{42;64}2{42;68;82;103} topologies, respectively. Compounds 3 and 4 are isostructural, in which [H4Mo8O28]4− clusters act as bidentate ligands to join 1D {[M(H3X)2]4+}n (M = Co or Ni) chains to generate a 2D layer. Moreover, the luminescent properties of compounds 1 and 2 have been investigated. The electrochemical study displays that compound 3 could be used as electrocatalysts in the electrical reduction of nitrite.