Synthesis, crystal structure and NLO property of a nonmetal pentaborate [C6H13N2][B5O6(OH)4]

A nonmetal pentaborate [C6H13N2][B5O6(OH)4] (1) has been synthesized by 1,4-diazabicyclo[2.2.2] octane (DABCO) and boric acid, and characterized by single-crystal X-ray diffraction, FTIR, elemental analysis, and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic system with space group Cc (no. 9), a=10.205(2) Å, b=14.143(3) Å, c=11.003(2) Å, β=113.97(3)°, V=1451.1(5) Å3, Z=4. The anionic units, [B5O6(OH)4]−, are interlinked via hydrogen bonding to form a three-dimensional (3D) supramolecular network containing large channels, in which the protonated [C6H13N2]+ cations are located. Second-harmonic generation (SHG) measurements on the powder samples reveal that 1 exhibits SHG efficiency approximately 0.9 times that of potassium dihydrogen phosphate (KDP).