The Indium Borate In₁₉B₃₄O₇₄(OH)₁₁ with T2 Supertetrahedra

The trigonal indium borate In₁₉B₃₄O₇₄(OH)₁₁ was synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 13 GPa and 1150 °C. The crystal structure could be determined by single-crystal X-ray diffraction data collected at room temperature. In₁₉B₃₄O₇₄(OH)₁₁ crystallizes in the trigonal space group <i>R</i>3̅ (Z = 3) with the lattice parameters <i>a</i> = 1802.49(6) pm, <i>c</i> = 1340.46(5) pm, and <i>V</i> = 3.7716(3) nm³. The structure of In₁₉B₃₄O₇₄(OH)₁₁ contains alternating B–O T2 supertetrahedra units. The presence of hydroxyl groups was confirmed with vibrational spectroscopic methods such as Raman and IR. Besides H₂InB₅O₁₀, In₁₉B₃₄O₇₄(OH)₁₁ is now the second known compound in the system In–B–O–H

New High-Pressure Gallium Borate Ga₂B₃O₇(OH) with Photocatalytic Activity

The new high-pressure gallium borate Ga₂B₃O₇(OH) was synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 10.5 GPa and 700 °C. For the system Ga–B–O–H, it is only the second known compound next to Ga₉B₁₈O₃₃(OH)₁₅·H₃B₃O₆·H₃BO₃. The crystal structure of Ga₂B₃O₇(OH) was determined by single-crystal X-ray diffraction data collected at room temperature. Ga₂B₃O₇(OH) crystallizes in the orthorhombic space group <i>Cmce</i> (<i>Z</i> = 8) with the lattice parameters <i>a</i> = 1050.7(2) pm, <i>b</i> = 743.6(2) pm, <i>c</i> = 1077.3(2) pm, and <i>V</i> = 0.8417(3) nm³. Vibrational spectroscopic methods (Raman and IR) were performed to confirm the presence of the hydroxyl group. Furthermore, the band gap of Ga₂B₃O₇(OH) was estimated via quantum-mechanical density functional theory calculations. These results led to the assumption that our gallium borate could be a suitable substance to split water photocatalytically, which was tested experimentally

Structural Redetermination and Photoluminescence Properties of the Niobium Oxyphosphate (NbO)₂P₄O₁₃

The structure of (NbO)₂P₄O₁₃ was solved and refined based on new single-crystal diffraction data revealing considerably more complexity than previously described. (NbO)₂P₄O₁₃ crystallizes in the triclinic space group <i>P</i>1̅ with <i>Z</i> = 6. The lattice parameters determined at room temperature are <i>a</i> = 1066.42(4) pm, <i>b</i> = 1083.09(4) pm, <i>c</i> = 1560.46(5) pm, α = 98.55(1)°, β = 95.57(1)°, γ = 102.92(1)°, and <i>V</i> = 1.7213(2) nm³. The superstructure contains 64 unique atoms including two disordered semioccupied oxygen positions. An unusual 180° bond angle between two [P₄O₁₃]^6– groups was refined to form half-occupied, split positions in agreement with previous reports. The IR and Raman spectra reflect the appearance of overlapping bands assignable to specific group vibrations as well as P–O–P linkages present in the [P₄O₁₃]^6– entities. Investigation of the powdered product concerning its photoluminescence properties revealed an excitability in the UV at 270 nm assigned to O2p–Nb4d charge transfer transitions. A resulting broad-band emission with the maximum in the visible region at 455 nm was determined