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The potential of cesium polysulfide-flux reactions for the synthesis of chalcogenogallates was investigated by using X-ray diffraction and Raman spectroscopy. An investigation of possible factors influencing the product formation revealed that only the polysulfide content x in the Cs2S x melts has an influence on the crystalline reaction product. From sulfur-rich melts (x > 7), CsGaS3 is formed, whereas sulfur-poor melts (x < 7) lead to the formation of Cs2Ga2S5. In situ investigations using high-temperature Raman spectroscopy revealed that the crystallization of these solids takes place upon cooling of the melts. Upon heating, CsGaS3 and Cs2Ga2S5 release gaseous sulfur due to the degradation of S2 2- units. This decomposition of CsGaS3 to Cs2Ga2S5 and finally to CsGaS2-mC16 was further studied in situ by using high-temperature X-ray powder diffraction. A combination of the polysulfide reaction route and the high-temperature decomposition leads to the possibility of the directed interconversion of these thiogallates. The presence of disulfide units in the anionic substructures of these thiogallates has a significant influence on the electronic band structures and their optical properties. This influence was studied by using UV/vis-diffuse reflectance spectroscopy and DFT simulations, revealing a trend of smaller band gaps with increasing S2 2- content. [ABSTRACT FROM AUTHOR]

A reinvestigation of the alkali metal thiosulfates has led to the new phase Cs2S2O3·H2O. At first cesium thiosulfate monohydrate was obtained as a byproduct of the synthesis of Cs4In2S5. Further investigations were carried out using the traditional synthesis reported by J. Meyer and H. Eggeling. Cs2S2O3·H2O crystallizes in transparent, colorless needles. The crystal structure of the title compound was determined by single crystal X-ray diffraction at room temperature: space group C2/ m (No. 12), unit cell dimensions: a = 11.229(4), b = 5.851(2), c = 11.260(5) Å, β = 95.89(2)°, with Z = 4 and a cell volume of V = 735.9(5) Å3. The positions of all atoms including the hydrogen atoms were located in the structure refinement. Cs2S2O3·H2O is isotypic with Rb2S2O3·H2O. Isolated tetrahedra [S2O3]2− are coordinated by the alkali metal cations, and in addition they serve as acceptors for hydrogen bonding. For both Cs atoms the shortest distances are observed to oxygen atoms of the S2O32− anions whereas the terminating sulfur atom has its shortest contacts to the water hydrogen atoms. Thus, an extended hydrogen bonding network is formed. The title compound has also been characterized by IR spectroscopy. IR spectroscopy reveals the vibrational bands of the water molecules at 3385 cm−1. They show a red shift in the OH stretching and bending modes as compared to free water. This is due both to the S···H hydrogen bonding and to the coordination of H2O molecules to the cesium atoms. [ABSTRACT FROM AUTHOR]

The reaction of CsN3 with GaS and S at elevated temperatures results in Cs2Ga2S5. Its crystal structure was determined from single-crystal X-ray diffraction data. The colorless solid crystallizes in space group C2/ c (no. 15) with V=1073.3(4) Å3 and Z=4. Cs2Ga2S5 is the first compound that features one-dimensional chains ${{{\hfill 1\atop \hfill \infty }}}$[Ga2S3(S2)2−] of edge- and corner-sharing GaS4 tetrahedra. The vibrational band of the S22− units at 493 cm−1 was revealed by Raman spectroscopy. Cs2Ga2S5 has a wide bandgap of about 3.26 eV. The thermal decomposition of CsN3 yields elemental Cs, which reacts with sulfur to provide Cs2S6 as an intermediate product. The crystal structure of Cs2S6 was redetermined from selected single crystals. The red compound crystallizes in space group ${P\bar 1}$ with V=488.99(8) Å3 and Z=2. Cs2S6 consists of S62− polysulfide chains and two Cs positions with coordination numbers of 10 and 11, respectively. Results of DFT calculations on Cs2Ga2S5 are in good agreement with the experimental crystal structure and Raman data. The analysis of the chemical bonding behavior revealed completely ionic bonds for Cs, whereas GaS and SS form polarized and fully covalent bonds, respectively. HOMO and LUMO are centered at the S2 units. [ABSTRACT FROM AUTHOR]

Cs2Ga2Se5 was obtained by the reaction of CsN3 with stoichiometric amounts of GaSe and Se at elevated temperature. It forms yellow crystals embedded in a pure orange microcrystalline powder. The crystal structure of Cs2Ga2Se5 was determined by single-crystal X-ray diffraction at 123 K. The compound crystallizes monoclinically in the space group C2/ c (No. 15) with a = 15.3911(5) Å, b = 7.3577(2) Å, c = 12.9219(3) Å, β = 126.395(3)°, V = 1177.89(7) Å3, and Z = 4. The structure features one-dimensional chains 1∞[Ga2Se3(Se2)2-], consisting of edge- and corner sharing GaSe4 tetrahedra. Raman spectroscopic measurements reveal vibrational bands of the Se22- units at 236 cm-1, and the bands of Ga-Se vibrations at 254 and 273 cm-1. UV/Vis diffuse reflectance spectroscopy shows the bandgap at about 1.95 eV. [ABSTRACT FROM AUTHOR]

Cs2Ga2Se5 was obtained by the reaction of CsN3 with stoichiometric amounts of GaSe and Se at elevated temperature. It forms yellow crystals embedded in a pure orange microcrystalline powder. The crystal structure of Cs2Ga2Se5 was determined by single-crystal X-ray diffraction at 123 K. The compound crystallizes monoclinically in the space group C2/ c (No. 15) with a = 15.3911(5) Å, b = 7.3577(2) Å, c = 12.9219(3) Å, β = 126.395(3)°, V = 1177.89(7) Å3, and Z = 4. The structure features one-dimensional chains 1∞[Ga2Se3(Se2)2-], consisting of edge- and corner sharing GaSe4 tetrahedra. Raman spectroscopic measurements reveal vibrational bands of the Se22- units at 236 cm-1, and the bands of Ga-Se vibrations at 254 and 273 cm-1. UV/Vis diffuse reflectance spectroscopy shows the bandgap at about 1.95 eV. [ABSTRACT FROM AUTHOR]

The new compounds Rb4Al2S5 (I) and Cs4In2S5 (II) are prepared by the azide route using RbN3 (CsN3), Al (In), and S in the molar ratio of 4:2:5 (evacuated quartz tubes, 500 °C, 8-10 d) which in case of compound (II) is repeated for 15 d. [ABSTRACT FROM AUTHOR]

The reaction of CsN3 with GaS and S at elevated temperatures results in Cs2Ga2S5. Its crystal structure was determined from single-crystal X-ray diffraction data. The colorless solid crystallizes in space group C2/ c (no. 15) with V=1073.3(4) Å3 and Z=4. Cs2Ga2S5 is the first compound that features one-dimensional chains ${{{\hfill 1\atop \hfill \infty }}}$[Ga2S3(S2)2−] of edge- and corner-sharing GaS4 tetrahedra. The vibrational band of the S22− units at 493 cm−1 was revealed by Raman spectroscopy. Cs2Ga2S5 has a wide bandgap of about 3.26 eV. The thermal decomposition of CsN3 yields elemental Cs, which reacts with sulfur to provide Cs2S6 as an intermediate product. The crystal structure of Cs2S6 was redetermined from selected single crystals. The red compound crystallizes in space group ${P\bar 1}$ with V=488.99(8) Å3 and Z=2. Cs2S6 consists of S62− polysulfide chains and two Cs positions with coordination numbers of 10 and 11, respectively. Results of DFT calculations on Cs2Ga2S5 are in good agreement with the experimental crystal structure and Raman data. The analysis of the chemical bonding behavior revealed completely ionic bonds for Cs, whereas GaS and SS form polarized and fully covalent bonds, respectively. HOMO and LUMO are centered at the S2 units. [ABSTRACT FROM AUTHOR]

Cs2Ga2S5 is prepared by slow thermal decomposition of CsN3 in presence of stoichiometric amounts of GaS and S in dynamic vacuum followed by annealing (quartz tube, 803 K, several d). [ABSTRACT FROM AUTHOR]