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Four new alkali metal aluminum/gallium iodates, namely A2M(IO3)4(H0.5IO3)2 (A = K, Rb and M = Al, Ga), have been successfully synthesized via a hydrothermal reaction and structurally characterized through single-crystal X-ray diffraction analysis. These compounds are isostructural and crystallize in the P1¯ space group (no. 2) with one formula unit in each unit cell. The rare half-protonated H0.5IO3 building units were identified, and their structure feature isolated [M(IO3)4(H0.5IO3)2]2− anions, which are separated by alkali metal cations. The optical diffuse reflectance spectroscopy measurements associated with the Tauc analysis showed direct energy gaps, which are in good agreement with the theoretical calculation prediction. Moreover, this study also indicates that the electronic properties of these compounds are mainly determined by the IO3 and H0.5IO3 anionic units, and the alkali metal cations show a remarkable effect on their energy gap values, whereas the impacts of the group 13 elements aluminum and gallium are insignificant. [ABSTRACT FROM AUTHOR]

We reported the synthesis and crystal structures of alkali metal and alkali-earth metal phosphite, namely, CsV 2 (H 3 O)(HPO 3 ) 4 ( 1 ), and Ba 3 V 2 (HPO 3 ) 6 ( 2 ). Both compounds were prepared by hydrothermal reactions and feature unique new structures. They both exhibit 3D complicated frameworks based on VO 6 octahedra which are connected by HPO 3 tetrahedra via corner-sharing. Alkali or alkali earth metal cations are filled in the different channels of the frameworks. Topological analysis shows that the framework of CsV 2 (H 3 O) (HPO 3 ) 4 ( 1 ) is a new 3,3,3,4,5-connected network with the Schläfli symbol of {4.6 2 } 2 {4 2 .6 6 .8 2 }{6 3 }{6 5 .8}. The investigations of X-ray photoelectron spectroscopy (XPS) and magnetic measurement on CsV 2 (H 3 O)(HPO 3 ) 4 suggest a +3 oxidation state of the vanadium ions in compound 1 . Photocatalytic performance was evaluated by photocatalytic H 2 evolution and degradation of methylene blue, which shows that both compounds exhibit activity under visible-light irradiation. IR spectrum, UV–vis-NIR spectrum and thermogravimetric analysis (TGA) of compounds were also investigated. [ABSTRACT FROM AUTHOR]

A new alkali-metal borogermanate with noncentrosymmetric structure, namely, Cs2GeB409, has been discovered, and a large crystal with dimensions of 20 × 16 × 8 mm(3) has been grown by a high-temperature top-seeded solution method using Cs2O-B2O2 as a flux. The compound crystallizes in the tetragonal space group I4 with a = b = 6.8063(2) Å, c = 9.9523(7) Å, V = 461.05(4) Å3, and Z = 2. It features a three-dimensional anionic open framework based on GeO4 tetrahedra and B4O9 clusters that are interconnected via corner-sharing, forming one-dimensional channels of nine-/ten-membered rings along the a and b axes, which are occupied by Cs+ cations. Cs2GeB409 exhibits a very high thermal stability with a melting point of 849 °C, and it possesses a short-wavelength absorption edge onset at 198 nm determined by UV-vis transmission spectroscopy measurements on a slab of polished crystal. Powder second-harmonic generation (SHG) measurement on sieved crystals reveals that Cs2GeB409 is a type I phase-matchable material with a strong SHG response of about 2.8 × KH2PO4. The preliminary investigation indicates that Cs2GeB409 is a new promising second-order nonlinear-optical crystalline material. [ABSTRACT FROM AUTHOR]