Three Inorganic-Organic Hybrid Gallo-/Alumino-Borates with Porous-Layered Structures Containing [MB4O10(OH)] (M = Al/Ga) Cluster Units.

Three inorganic-organic hybrid gallo-/alumino-borates [Ga2B7O14(OH)]·H2dah (1, dah = 1,6-diaminohexane), K2[Ga2B7O14(OH)(en)0.5] (2, en = ethylenediamine), and K2[Al2B7O14(OH)(en)0.5]·H2O (3) were synthesized under solvothermal conditions. Compound 1 features a 3D porous-layered structure built by the alternation of [GaB4O10(OH)]6-, [B3O6]3- clusters and GaO4 tetrahedra, in which the novel [GaB4O10(OH)]6- cluster is first observed. Compounds 2 and 3 are isostructural and made by [MB4O10(OH)]6-, [B3O6(en)0.5]3- clusters and MO4 tetrahedra (M = Ga/Al); their 3D porous layers are similar to those of 1 and further bridged by en linkers through the rare B-N-C covalent bonds, resulting in the 3D inorganic-organic hybrid framework. This is the first main-group metal borate with organic molecules participating in the oxoboron frameworks through B-N bonds. Optical diffuse-reflectance spectra reveal that 1, 2, and 3 are potential wide-band-gap semiconductors.