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)].0.25H(2)O (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.