Hydrothermal synthesis, structure and characterization of a novel layered vanadium oxide with metal coordination complexes: [Ni(en)2][V6O14]

Abstract

The hydrothermal reaction of V₂O₅, Ni(NO₃)₂·6H₂O, ethylenediamine and H₂O in the molar ratio of 1∶1∶3.5∶519 at 180 °C yields black plates of [Ni(en)₂][V₆O₁₄]. This compound has been characterized structurally, magnetically, electrically, and spectroscopically. The crystal structure consists of novel mixed-valence vanadium oxide layers and interlayer metal coordination complexes. Each of the three VO₅ square pyramids share two edges to form a V₃O₁₁ group. The V₃O₁₁ groups are connected through sharing edges to produce a linear ribbon. Adjacent strips share corners to form a layer structure. The two oxygen atoms from the neighbouring vanadium oxide layers are coordinated to each nickel atom in a trans-fashion, and form a three-dimensional framework structure. An EHT (Extended Hückel Theory) calculation was performed to analyze the electronic structure, and the electrical resistivity measurements confirmed the expected semiconducting behavior of [Ni(en)₂][V₆O₁₄].