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

A case of hydrous borate with the formula of Ba 2 B 13 O 19 (OH) 5 ·5H 2 O was synthesized by the traditional hydrothermal method . It crystallizes in the chiral P 1 space group and has a unique two-dimensional 2 [B 13 O 19 (OH) 5 ] ∞ layer that is constructed by the hydrogen involved [B 13 O 22 (OH) 5 ] fundamental building blocks (FBBs). The Ba atoms and H 2 O molecules are filled in the three-dimensional pore constructed by the 2 [B 13 O 19 (OH) 5 ] ∞ layer. Interestingly, Ba 2 B 13 O 19 (OH) 5 ·5H 2 O is the first case of hydrous borates that has the above rare [B 13 O 22 (OH) 5 ] FBB and 2 [B 13 O 19 (OH) 5 ] ∞ layer, which enriching the structural chemistry of borate system. The diffuse reflection spectrum result shows that the ultraviolet (UV) cutoff edge of Ba 2 B 13 O 19 (OH) 5 ·5H 2 O 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 [B 13 O 22 (OH) 5 ] groups are the main sources of SHG effects.