New vanadium tellurites: Syntheses, structures, optical properties of noncentrosymmetric VTeO₄(OH), centrosymmetric Ba₂V₄O₈(Te₃O₁₀)

Two new vanadium tellurites, VTeO₄(OH) (1) and Ba₂V₄O₈(Te₃O₁₀) (2), have been synthesized successfully with the use of hydrothermal reactions. The crystal structures of the two compounds were determined by single-crystal X-ray diffraction. Compound 1 crystallizes in the polar space group Pca2₁ (No. 29) while compound 2 crystallizes in the centrosymmetric space group C2/c (No. 15). The topography of compound 1 reveals a two-dimensional, layered structure comprised of VO₆ octahedral chains and TeO₃(OH) zig-zag chains. Compound 2, on the contrary, features a three-dimensional [V₄O₈(Te₃O₁₀)]^4- anionic framework with Ba²⁺ ions filled into the 10-member ring helical tunnels. The [V₄O₈(Te₃O₁₀)]^4- anionic network is the first 3D vanadium tellurite framework to be discovered in the alkaline-earth vanadium tellurite system. Powder second harmonic generation (SHG) measurements indicate that compound 1 shows a weak SHG response of about 0.3×KDP (KH₂PO₄) under 1064 nm laser radiation. Infrared spectroscopy, elemental analysis, thermal analysis, and dipole moment calculations have also been carried out. - Graphical abstract: VTeO₄(OH) (1) crystallizes in the noncentrosymmetric space group Pca2₁ (No. 29) while Ba₂V₄O₈(Te₃O₁₀) (2) crystallizes in the centrosymmetric space group C2/c (No. 15). - Highlights: • VTeO₄(OH) (1) and Ba₂V₄O₈(Te₃O₁₀) (2) have been synthesized successfully with the use of hydrothermal reactions. • VTeO₄(OH) (1) crystallizes in the noncentrosymmetric space group Pca2₁ and displays a weak SHG response. • VTeO₄(OH) (1) represents only the fourth SHG-active material found in vanadium tellurite systems. • Ba₂V₄O₈(Te₃O₁₀) (2) exhibits a novel three-dimensional [V₄O₈(Te₃O₁₀)]^4- anionic framework.