A Mixed-Valence Vanadate as Model for the Vanadium Mineral Melanovanadite: Hydrothermal Synthesis, Crystal Structure and Magnetic Properties of MgV^V₂V^IV₂O₁₀·4H₂O

Abstract

A mixed-valence vanadate, MgVV 2VIV 2O10·4H2O (1), has been synthesized hydrothermally and characterized by single-crystal X-ray diffraction, spectroscopic and thermogravimetric analyses, and temperature dependent magnetic measurements. The compound shows magnetic properties with domination of intrasheet exchange interactions versus intersheet interactions due to large distance between vanadate sheets. It represents a synthetic analogue of the mineral melanovanadite: Ca2VV 4VIV 4O20·10H2O. The framework structure in 1 consists of vanadium oxide layers cross-linked by {Mg (H2O)4} groups. The vanadium oxide layers are composed of edge shared {VIVO5} square pyramids, forming {V2O8} dimers, which share corners with {VVO4} tetrahedral units. Crystal data for 1: triclinic space group P1̅ with a = 6.3232(14) Å, b = 6.3917(14) Å, c = 7.9388(17) Å, α = 88.264(19)°, β = 67.428(16)°, γ = 79.433(20)°, V = 290.97(12) Å3, Z = 1.