Ba2B13O19(OH)5·5H2O: A promising nonlinear optical material with a unique 2[B13O19(OH)5]∞ two-dimensional layer

Abstract

A case of hydrous borate with the formula of Ba2B13O19(OH)5·5H2O was synthesized by the traditional hydrothermal method. It crystallizes in the chiral P1 space group and has a unique two-dimensional 2[B13O19(OH)5]∞ layer that is constructed by the hydrogen involved [B13O22(OH)5] fundamental building blocks (FBBs). The Ba atoms and H2O molecules are filled in the three-dimensional pore constructed by the 2[B13O19(OH)5]∞ layer. Interestingly, Ba2B13O19(OH)5·5H2O is the first case of hydrous borates that has the above rare [B13O22(OH)5] FBB and 2[B13O19(OH)5]∞ layer, which enriching the structural chemistry of borate system. The diffuse reflection spectrum result shows that the ultraviolet (UV) cutoff edge of Ba2B13O19(OH)5·5H2O is below 200 nm. Its second harmonic generation (SHG) response is approximately 1.0 times that of potassium dihydrogen phosphate at the 1064 nm fundamental wavelength and it is also phase-matchable. Both results indicate that the title compound is a nonlinear optical crystal for UV spectral region. Theoretical simulation calculation shows that the occupied VE states are mainly contributed by the O-2p orbitals, and therefore [B13O22(OH)5] groups are the main sources of SHG effects.