From discrete borate cluster to three-dimensional open framework

Abstract

Two new borates [NH₃(CH₂)₂NH(CH₂)₂NH₃]₂[B₁₄O₂₀(OH)₆] (1) and [NH₃(CH₂)₂NH(CH₂)₂NH₃]₂[Al₂B₁₀O₂₀]·4H₂O (2) have been synthesized in the presence of the same organic amine (diethylenetriamine) under hydro(solvo)thermal conditions. 1 is an isolated structure containing a large ring-shape polyborate cluster [B₁₄O₂₀(OH)₆]⁴⁻. The structural building units (SBUs) of 2 are the [B₅O₁₀]⁵⁻ cluster anions and AlO₄ tetrahedra, which are alternately joined to form a three-dimensional framework with 11-membered rings (MRs). 2 crystallizes in the chiral space group P2₁ and displays good second harmonic generation (SHG) efficiencies of about 2.0 times that of the value of KDP (KH₂PO₄). Though the same structure-directing agents (SDAs) were introduced under similar reaction conditions, 1 and 2 have very different chemical compositions and structures. To our knowledge, this is the first such observation in the family of the organoamine-templated borates.