New Series of Polar and Nonpolar Platinum Iodates A2Pt(IO3)6 (A = H3O, Na, K, Rb, Cs).

A new series of platinum iodates, namely, α-(H3O)2Pt(IO3)6, β-(H3O)2Pt(IO3)6, and A2Pt(IO3)6 (A = Na, K, Rb, Cs), have been synthesized. Interestingly, among these six stoichiometrically identical compounds, α-(H3O)2Pt(IO3)6 is polar, whereas other compounds are nonpolar and centrosymmetric. They all consist of zero-dimensional [Pt(IO3)6](2-) molecular units separated by H3O(+) or A(+) cations. All of the lone electron pairs of the IO3(-) groups are aligned and almost point to one direction for α-(H3O)2Pt(IO3)6, whereas IO3(-) groups are located trans to each other in other compounds. The material, α-(H3O)2Pt(IO3)6, exhibits very strong second harmonic generation (SHG) effects, approximately 1.2 × KTiOPO4 (KTP), and is phase-matchable. Thermogravimetric analysis, elemental analysis, infrared spectra, UV-vis spectra, nonlinear optical properties, and theoretical calculations are also reported.