Synthesis, Structure, and Characterization of d0 Transition-Metal Iodate: BaTi(IO3)6·0.5H2O.

A new noncentrosymmetric (NCS) d0 transition-metal (TM) iodate BaTi(IO3)6·0.5H2O has been successfully synthesized by the typical hydrothermal method. The single-crystal X-ray diffraction shows that BaTi(IO3)6·0.5H2O crystallizes in the polar trigonal space group R3 (no. 146) with a = b = 11.1920(12) Å, c = 24.006(3) Å. The reported compound features zero-dimensional (0D) [Ti(IO3)6]2- clusters that are separated by Ba2+ cations and bound water in the structure. By comparing BaTi(IO3)6·0.5H2O with the centrosymmetric (CS) α- and β-BaTi(IO3)6 that were reported before, it can be found that the bound water plays an important role for the formation of NCS structure for BaTi(IO3)6·0.5H2O. In addition, based on the powder second harmonic (SHG) measurement, BaTi(IO3)6·0.5H2O can achieve type-I phase matching with a moderate SHG effect (∼1 × KDP). The source of SHG effect was analyzed by dipole moment calculation and structure comparison. UV-vis-NIR diffuse reflectance spectroscopy, infrared spectroscopy, and thermogravimetric measurements are also presented.