K₂Au(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.

HBa2.5(IO3)6(I2O5) and HBa(IO3)(I4O11): Explorations of Second-Order Nonlinear Optical Materials in the Alkali-Earth Polyiodate System

“…Calculations of the dipole moments were calculated on the polar compound with the method previously reported (Table S3 in the Supporting Information) . The local dipole moments for the IO 3 units were calculated to be 14.03–17.37 D for HBa 2.5 (IO 3 ) 6 (I 2 O 5 ), which are in accordance with the reported values. − For the polar compound HBa 2.5 (IO 3 ) 6 (I 2 O 5 ), the calculated a and b -components of the polarization from the IO 3 units in a unit cell are cancelled out, while the c -components are added up, leading to a net dipole moment of the structure. The dipole moments per unit volume of HBa 2.5 (IO 3 ) 6 (I 2 O 5 ) is 0.068 D Å –3 , which is a relatively small value, in accordance with the moderate SHG response.…”

Bi(IO3)F2: The First Metal Iodate Fluoride with a Very Strong Second Harmonic Generation Effect

“…The local dipole moment of the I1O 3 unit was calculated to be 14.90 D, which compares well with those of IO 3 groups reported previously . Each unit cell contains four I1O 3 units, and the x and z components of the polarizations from the four IO 3 groups within one unit cell cancel each other out completely while the y components add up to a net dipole moment of 54.96 D. Taking into consideration the unit‐cell volume, the dipole moment per unit volume of Bi(IO 3 )F 2 was calculated to be 0.135 D Å −3 , which is comparable to those of other reported polar iodates with excellent SHG effects, for example, K 2 Au(IO 3 ) 5 (0.114 D Å −3 ) . Dipole moment calculations were also conducted for BiOIO 3 , which gave values of 15.16 D for the local dipole moment of the IO 3 group and 0.168 D Å −3 for the dipole moment per unit volume.…”

Two Polar Molybdenum(VI) Iodates(V) with Large Second-Harmonic Generation Responses

“…Among all known iodates, there are only two types of coordination geometries of the I 5+ cation, i.e., [IO 3 ] − and [IO 4 ] 3– units, if the weak I–O interactions (I–O bond lengths of >2.4 Å) are neglected. The “isolated” [IO 3 ] − units are common, and they are observed in PbPt­(IO 3 ) 6 (H 2 O), ABi 2 (IO 3 ) 2 F 5 (A = K, Rb, and Cs), K 2 Au­(IO 3 ) 5 , Bi­(IO 3 )­F 2 , Ba­(MoO 2 ) 2 (IO 3 ) 4 O, etc. The neutral dimeric [I 2 O 5 ] units formed by two corner-sharing [IO 3 ] − units could also be observed in Rb 3 (IO 3 ) 3 (I 2 O 5 )­(HIO 3 ) 4 (H 2 O) and HIO 3 (I 2 O 5 ) .…”