New Metal Iodates: Syntheses, Structures, and Characterizations of Noncentrosymmetric La(IO₃)₃ and NaYI₄O₁₂ and Centrosymmetric β-Cs₂I₄O₁₁ and Rb₂I₆O₁₅(OH)₂·H₂O

Four new metal iodates, β-Cs2I4O11, Rb2I6O15(OH)2·H2O, La(IO3)3, and NaYI4O12, have been synthesized hydrothermally, and the structures were determined by single-crystal X-ray diffraction techniques. All of the reported materials contain I5+ cations that are in asymmetric coordination environments attributable to their stereoactive lone pair. Second-order nonlinear optical measurements on noncentrosymmetric La(IO3)3 and NaYI4O12, using 1064-nm radiation, indicate that both materials have second-harmonic-generating properties with efficiencies of approximately 400 × SiO2. Converse piezoelectric measurements revealed d33 values of 5 and 138 pm V-1 for La(IO3)3 and NaYI4O12, respectively. Infrared and Raman spectroscopy and thermogravimetric analyses are also presented for all of the reported materials. Crystal data: β-Cs2I4O11, monoclinic, space group P21/n (No. 14), with a = 12.7662(14) Å, b = 7.4598(8) Å, c = 14.4044(16) Å, β = 106.993(2)°, V = 1311.9(2) Å3, and Z = 4; Rb2I6O15(OH)2·H2O, triclinic, space group P1̄ (No. 2), with a = 7.0652(17) Å, b = 7.5066(18) Å, c = 18.262(4) Å, α = 79.679(4)°, β = 85.185(4)°, γ = 70.684(4)°, V = 898.9(4) Å3, and Z = 2; La(IO3)3, monoclinic, space group Cc (No. 9), with a = 12.526(2) Å, b = 7.0939(9) Å, c = 27.823(4) Å, β = 101.975(4)°, V = 2418.4(6) Å3, and Z = 4; NaYI4O12, monoclinic, space group Cc (No. 9), with a = 31.235(3) Å, b = 5.5679(5) Å, c = 12.5451(12) Å, β = 91.120(3)°, V = 2181.3(4) Å3, and Z = 4.