Variations on a One-Dimensional Theme: The Hydrothermal Syntheses of Inorganic/Organic Composite Solids of the Iron Molybdate Family

The hydrothermal reactions of molybdenum oxide starting materials with iron(II) and iron(III) halides in the presence of 2,2′-bipyridine have afforded the three related one-dimensional solid materials [MoO₄{Fe(III)Cl(2,2′-bpy)}] (1), [Mo₃O₁₂{Fe(III)(2,2′-bpy)} ₂]·0.25H₂O (2), and [Mo₄O₁₅{Fe(III)(2,2′-bpy)}₂] (3). The structures of these three materials are based on a common one-dimensional ribbon exhibited by 1. The ribbon is constructed from four-polyhedra rings consisting of two {MoO₄} tetrahedra and two {FeXN₂O₃} (X = Cl for 1, O for 2 and 3) octahedra. These polyhedra corner share such that each molybdenum center serves to bridge the two iron octahedra in the ring. Attachment to the next such four-ring is through the third corner sharing interaction of each molybdenum tetrahedron. Replacement of the pendant chloride substituents on adjacent iron centers in 1 with an {MoO₄} unit leads to compound 2, while an {Mo₂O₇} linkage between adjacent iron centers affords 3.