Supramolecular assembly of borate with quaternary ammonium: Crystal structure and tunable luminescent properties

A new borate [C6H16N][B5O6(OH)(4)] (1) is synthesized hydrothermally by the reaction of isopropyltri-methylammonium hydroxide with boric acid. It crystallizes in the triclinic space group P-1 with the parameters a=9.1578(10) angstrom, b=9.372(9) angstrom, c=9.9812(10) angstrom, alpha=66.508(2)degrees, beta=74.751(2)degrees, gamma=81.893(2)degrees. The [B5O6(OH)(4)](-) anions are interlinked via hydrogen bonding forming a 3D supramolecular network containing large cavities, where reside the (CH3)(3)(i-C3H7) N+ cations. This borate shows tunable luminescent properties with temperature, heating-treatment, exciting-light, and solvents. The fluorescent intensity of 1 enhances 6-fold with decreasing the temperature from 25 K to 78 K. By treatment under different temperatures, the luminescence of I shifted from blue to white and the sample treated at 230 degrees C emits bright white light to naked eyes. The hybrid borate can disperse in different solvents, and shows a red-shifted and intense emission in polar solvents. (C) 2013 Elsevier Inc. All rights reserved.