Synthesis, Structure, and Characterization of Transition-Metal Iodate: BaTi(IO)·0.5HO.

A new noncentrosymmetric (NCS) transition-metal (TM) iodate BaTi(IO)·0.5HO has been successfully synthesized by the typical hydrothermal method. The single-crystal X-ray diffraction shows that BaTi(IO)·0.5HO crystallizes in the polar trigonal space group 3 (no. 146) with = = 11.1920(12) Å, = 24.006(3) Å. The reported compound features zero-dimensional (0D) [Ti(IO)] clusters that are separated by Ba cations and bound water in the structure. By comparing BaTi(IO)·0.5HO with the centrosymmetric (CS) α- and β-BaTi(IO) that were reported before, it can be found that the bound water plays an important role for the formation of NCS structure for BaTi(IO)·0.5HO. In addition, based on the powder second harmonic (SHG) measurement, BaTi(IO)·0.5HO 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.