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.