Hydrothermal syntheses and structural characterizations of organic-inorganic hybrid materials of the M(II)-ligand/vanadium oxide system (M(II) = Cu(II) and Zn(II); ligand = 2,2′-bipyridine and 2,2′:6′,2″-terpyridine)

Investigation into the incorporation of complex transition metal-organic units into vanadium oxide structures has resulted in the preparation of several novel composite materials. Hydrothermal reactions of V₂O₅, 2,2′-bipyridine, an appropriate Zn or Cu starting material, and H₂O under a variety of conditions yielded the organic-inorganic hybrid materials [{Zn(2,2′-bpy)}₂V₄O₁₂] (1) and [Cu(2,2′-bpy)V₄O_10.5] (2). Blocking an additional coordination site on the secondary metal center by using a tridentate organonitrogen ligand, 2,2′:6′,2″-terpyridine in place of 2,2′-bipyridine, allowed the isolation of [Cu(terpy)V₂O₆] (3) and [{Zn(terpy)}₂V₆O₁₇] (4). The structure of 1 is a two-dimensional zinc vanadate layer, composed of rings containing four comer-sharing {VO₄} vanadium(V) tetrahedra linked through six zinc square pyramids, with the 2,2′-bipyridine groups attached to the zinc centers and directed above and below the plane of the layer. In contrast to 1, the layer of 2 is based on a two-dimensional vanadium oxide substructure composed of vanadium(IV) square pyramids and vanadium(V) tetrahedra with copper square pyramids attached through corner-sharing interactions with vanadium tetrahedra such that the bipyridine ligands attached to the copper sites form staggered stacks above and below the plane of the layer. Compound 3 consists of one-dimensional vanadium oxide chains of corner-sharing tetrahedra linked through copper-terpyridine units into a two-dimensional bimetallic oxide of composition {CuV₂O₆}, while the layer structure of 4 contains more complex one-dimensional vanadium oxide chains composed of fused rings of six corner-sharing vanadium oxide tetrahedra which are linked into a layer through {Zn(terpy)}²⁺ units.