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

摘要

Systematic explorations of new compounds in the La~(3+)-V ~(4+)/V~(5+)-iodate system led to three new lanthanum(iii) vanadium iodates, namely, LaVO(IO_3)_5, LaV _2O_6(IO_3), and LaVO_2(IO _3)_4·H_2O. LaVO(IO_3) _5 is isostructural with LaTiO(IO_3)_5 and its structure contains a 0D [VO(IO_3)_5]~(3-) anionic unit composed of one VO_6 octahedron linked to five IO _3~- groups. Such 0D anionic units are separated by La ~(3+) ions. LaV_2O_6(IO_3) exhibits a unique 3D framework composed of 1D [V_2O_6]~(2-) ladder like chains and 2D [La(IO_3)]~(2+) layers. LaVO _2(IO_3)_4·H_2O is isostructural with LnMoO_2(IO_3)_4(OH) (Ln = La, Nd, Sm, Eu) with a polar space group P2_1, its structure contains a novel 0D [VO_2(IO_3)_4]~(3-) anionic unit composed of one VO_6 octahedron linked with four IO_3~- groups and two terminal O~(2-) anions. Such 0D anionic units are separated by La~(3+) ions. The structure of LaVO_2(IO _3)_4·H_2O can also be described as the 8-MR channels of the 3D [La(IO_3)_4]~- anion being filled by the VO_6 octahedra and lattice water molecules. LaVO _2(IO_3)_4·H_2O 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.