M6[Cd2(CO3)2(B12O18)(OH)6] (M = K, Rb): Borate-Carbonates with Two CdCO3 Embedded in a Cyclic Oxoboron Anion

Two metal borate-carbonates, M6[Cd2(CO3)2(B12O18)(OH)6] [M = K (1), Rb (2)], were obtained under surfactant-thermal conditions. In 1 and 2, each cyclic [(B12O18)(OH)6]6- anion captures two CdCO3 in two sides of the rings and finally forms the unusual (CdCO3)2@[(B12O18)(OH)6] cluster. Both 1 and 2 show moderate birefringence. Density functional theory calculations indicate that carbonate groups have a major contribution to electron-related optical transition.

Magnesium cations as templates for the self-assembly of supramolecular luminescent {Mg@[B18φ34-35]}-clusters

Solvothermal reaction of magnesium nitrate and boron oxide in N,N-dimethylformamide produced a number of particularly complex supramolecular magnesium borates. Five topologically different types of negatively charged {Mg@[B18φ34-35]}-clusters, φ = O, OH, were observed with the magnesium cation as a core and octadecaborate anions as shells. The clusters assemble via common borate polyhedra forming 1D chains, a 2D mesoporous layer, and 3D mesoporous frameworks with an effective channel width of up to 16 Å. Topological analysis of the clusters in combination with the modular crystallography approach indicates that numerous new functional materials can be obtained by varying their assembly mode. At least one compound containing such clusters exhibits a very strong luminescence.

Two New Aluminoborates with 3D Porous-Layered Frameworks

Two new aluminoborates, NaKCs[AlB₇O₁₃(OH)]·H₂O (1) and K₄Na₅[AlB₇O₁₃(OH)]₃·5H₂O (2), have been hydro(solvo)thermally made with mixed alkali metal cationic templates. Both 1 and 2 crystallize in the monoclinic space group P2₁/n and contain similar units of [B₇O₁₃(OH)]^6- cluster and AlO₄ tetrahedra. The [B₇O₁₃(OH)]^6- cluster is composed of three classical B₃O₃ rings by vertex sharing, of which two of them connect with AlO₄ tetrahedra to constitute monolayers, and one provides an O atom as a bridging unit to link two oppositely orientated monolayers by Al-O bonds to form 3D porous-layered frameworks with 8-MR channels. UV-Vis diffuse reflectance spectra indicate that both 1 and 2 exhibit short deep-UV cutoff edges below 190 nm, revealing that they have potential applications in deep-UV regions.

Crystal structure of Rb6[B12O18(OH)6]·2H2O

The solvothermal reaction of H3BO3, sodium tert-butoxide, Rb2CO3 and pyridine led to a new alkaline metal borate hexa-rubidium hexa-hydroxy-dodeca-borate dihydrate, Rb6[B12O18(OH)6]·2H2O. Its structure contains a large cyclic dodeca-oxoboron cluster, [B12O18(OH)6]6-, formed by six {B3O3} rings. In the crystal, O-H⋯O hydrogen bonds between the components lead to the formation of a three-dimensional supra-molecular framework.

Two layered galloborates from centric to acentric structures: syntheses and NLO properties

Two layered galloborates (GBOs), Na₃GaB₄O₉ (1) and Na₅Ga[B₇O₁₂(OH)]₂·2B(OH)₃ (2), have been solvothermally made. 1 exhibits an unprecedented layer built by GaO₄ tetrahedra and B₄O₉ clusters. 2 was made by raising the ratio of B/Ga and the reaction temperature of 1, featuring a 2D acentric layer built by GaO₄ groups and B₇O₁₃(OH) clusters. 2 shows the highest second-harmonic generation (SHG) response of 4.6 times that of KDP (KH₂PO₄) among main group metal borates (MBOs).

Syntheses, structures and optical properties of two B3O7 cluster-based borates

1 is a 2D fluctuant layered borate made from two different B3O7 clusters. 2 features a 3D open framework with large 17-MR channels filled with Li-BO(OH)2-Ca chains.