title: K2 Au(IO3)5 and β-KAu(IO3)4: Polar Materials with Strong SHG Responses Originating from Synergistic Effect of AuO4 and IO3 Units.
abstract: Two new polar potassium gold iodates, namely, K2 Au(IO3)5 (Cmc21) and β-KAu(IO3)4 (C2), have been synthesized and structurally characterized. Both compounds feature zero-dimensional polar [Au(IO3)4](-) units composed of an AuO4 square-planar unit coordinated by four IO3(-) ions in a monodentate fashion. In β-KAu(IO3)4, isolated [Au(IO3)4](-) ions are separated by K(+) ions, whereas in K2 Au(IO3)5, isolated [Au(IO3)4](-) ions and non-coordinated IO3(-) units are separated by K(+) ions. Both compounds are thermally stable up to 400 °C and exhibit high transmittance in the NIR region (λ=800-2500 nm) with measured optical band gaps of 2.65 eV for K2 Au(IO3 )5 and 2.75 eV for β-KAu(IO3)4. Powder second-harmonic generation measurements by using λ=2.05 μm laser radiation indicate that K2 Au(IO3)5 and β-KAu(IO3)4 are both phase-matchable materials with strong SHG responses of approximately 1.0 and 1.3 times that of KTiOPO4, respectively. Theoretical calculations based on DFT methods confirm that such strong SHG responses originate from a synergistic effect of the AuO4 and IO3 units.
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, 350002, P.R. China), Fax.
authors.forename: Xiang
authors.initials: X
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, 350002, P.R. China), Fax.
authors.forename: Chun-Li
authors.initials: CL
authors.lastname: Hu
authors.affiliation: Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, 350002, P.R. China.
authors.forename: Bing-Xuan
authors.initials: BX
authors.lastname: Li
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, 350002, P.R. China), Fax. mjg@fjirsm.ac.cn.
authors.forename: Jiang-Gao
authors.initials: JG
authors.lastname: Mao
keywords: iodine; polar material; second-harmonic generation; single-crystal structures; synergistic effects