Synthesis, structure and characterization of Pr[B5O8(OH)]NO3.2H2O

A new rare earth metal borate crystalline compound Pr[B5O8(OH)]NO3.2H2O (1) containing nitrate anions was obtained using a hydrothermal method. The crystal structure was examined using single-crystal X-ray diffraction. The compound crystallises in the monoclinic system (space group P21/n) with a = 6.4619(5) angstrom, b = 15.4518(13) angstrom, c = 10.5754(8) angstrom, beta = 90.357(2)degrees and V = 1055.91(14) angstrom 3. The basic building block of the compound was [B5O10(OH)]6-polyanion cluster, which forms a two-dimensional B-O layered structure; The Pr3+ ions fill the windows of the B-O layers, whereas the nitrates and water molecules occupy the gaps between the B-O layers. The crystal structure was further characterised using powder diffraction, infrared transmission spectroscopy and thermogravimetric analysis. In addition, the solid-state fluorescence emission spectra of the crystal were measured, showing the characteristic emission peaks of Pr3+.