A mixed-valence vanadate as model for the vanadium mineral melanovanadite: Hydrothermal synthesis, crystal structure and magnetic properties of MgV ~V _2V ~(IV) _2O _(10)?4H _2O

摘要

A mixed-valence vanadate, MgV ~V _2V ~(IV) _2O _(10)?4H _2O (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: Ca _2V ~V _4V ~(IV) _4O _(20)?10H _2O. The framework structure in 1 consists of vanadium oxide layers cross-linked by {Mg (H _2O) _4} groups. The vanadium oxide layers are composed of edge shared {V ~(IV)O _5} square pyramids, forming {V _2O _8} dimers, which share corners with {V ~VO _4} tetrahedral units. Crystal data for 1: triclinic space group P1? with a = 6.3232(14) ?, b = 6.3917(14) ?, c = 7.9388(17) ?, α = 88.264(19)°, β = 67.428(16)°, γ = 79.433(20)°, V = 290.97(12) ? 3, Z = 1.