Syntheses, crystal structures, and properties of three new lanthanum(iii) vanadium iodates

Abstract

Systematic explorations of new compounds in the La³⁺–V⁴⁺/V⁵⁺-iodate system led to three new lanthanum(III) vanadium iodates, namely, LaVO(IO₃)₅, LaV₂O₆(IO₃), and LaVO₂(IO₃)₄·H₂O. LaVO(IO₃)₅ is isostructural with LaTiO(IO₃)₅ and its structure contains a 0D [VO(IO₃)₅]³⁻ anionic unit composed of one VO₆ octahedron linked to five IO₃⁻ groups. Such 0D anionic units are separated by La³⁺ ions. LaV₂O₆(IO₃) exhibits a unique 3D framework composed of 1D [V₂O₆]²⁻ ladder like chains and 2D [La(IO₃)]²⁺ layers. LaVO₂(IO₃)₄·H₂O is isostructural with LnMoO₂(IO₃)₄(OH) (Ln = La, Nd, Sm, Eu) with a polar space group P2₁, its structure contains a novel 0D [VO₂(IO₃)₄]³⁻ anionic unit composed of one VO₆ octahedron linked with four IO₃⁻ groups and two terminal O²⁻ anions. Such 0D anionic units are separated by La³⁺ ions. The structure of LaVO₂(IO₃)₄·H₂O can also be described as the 8-MR channels of the 3D [La(IO₃)₄]⁻ anion being filled by the VO₆ octahedra and lattice water molecules. LaVO₂(IO₃)₄·H₂O displays a weak SHG response of about 0.2 times that of KDP. Optical, thermal stability and magnetic susceptibility measurements as well as theoretical calculations have also been performed.