A new series of platinum iodates, namely, alpha-(H3O)(2)Pt(IO3)(6),beta-(H3O)(2)Pt(IO3)(6), and A(2)Pt(IO3)(6) (A = Na, K, Rb, Cs), have been synthesized. Interestingly, among these six stoichiometrically identical compounds, alpha-(H3O)(2)Pt(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 alpha-(H3O)(2)Pt(IO3)(6), whereas IO3- groups are located trans to each other in other compounds. The material, alpha-(H3O)(2)PT(IO3)(6), exhibits very strong second harmonic generation (SHG) effects, approximately 1.2 X KTiOPO4 (KTP), and is phase-matchable. Thermogravimetric analysis, elemental analysis, infrared spectra, UV-vis spectra, nonlinear optical properties, and theoretical calculations are also reported.