Square‐Planar Noble Metal Iodate [M(IO₃)₄]^n– (M = Pd^II, Au^III; n = 2, 1) Anions and Their Ability to Form Polar and Centrosymmetric Architectures

K2Au(IO3)5 and β‐KAu(IO3)4: Polar Materials with Strong SHG Responses Originating from Synergistic Effect of AuO4 and IO3 Units

“…À ions as those in a-KAu(IO 3 ) 4 (P1) reported by Albrecht-Schmitt et al, [23] but the local symmetry of the [Au(IO 3 ) 4 ]…”

Structures and properties of functional metal iodates

“…The lone pairs of IO 3 iodate groups are aligned trans to each other (oriented in opposite directions), which resulted in the cancellation of their local dipole moments, hence it is non-polar. The structure of K 2.5 Pd(IO 3 ) 4 (H 0.5 IO 3 ) (C2/m, CS) features a 0D [Pd(IO 3 ) 4 ] 2 anionic unit which is composed of a PdO 4 square unit corner-sharing with four iodate groups, such anionic units are separated by the K + cations and "isolated" HIO 3 groups [52]. It is interesting to note that all of the four iodate anions in the [Pd(IO 3 ) 4 ] 2 anionic unit are aligned on the same side of the PdO 4 square plane, therefore such anionic unit is polar.…”

“…For example, Li 2 Ti(IO 3 ) 6 and Na 2 Ti(IO 3 ) 6 are isostructural and polar with strong SHG responses of 500 and 400 times that of -SiO 2 respectively whereas A 2 Ti(IO 3 ) 6 (M = K, Rb, Cs, Tl) are structurally centrosymmetric (CS) [48,49]. Recently, transition metal ions with a square planar coordination geometry, such as gold(III) and palladium(II), also have been used to prepare new metal iodates [52,53]. The combination of another types of lone-pair cations (Pb 2+ and Bi 3+ ) with I(V) cations in the same compound were also reported [54][55][56][57][58][59].…”

Recent advances on second-order NLO materials based on metal iodates

“…So far, such compounds are still rare and the d 8 -TM ions are mainly gold(III) and palladium(II) [117][118][119]. The NCS metal iodates containing a square planar d 8 -TMO 4 unit are listed in Table 5.…”

“…A number of metal iodates containing polyiodate anions (I O I bridges) possess very large SHG effects [73][74][75][76]. Several synthetic strategies have been developed successfully to design new metal iodates with excellent SHG properties, such as the introduction of other lone pair containing cations such as Pb 2+ and Bi 3+ [78][79][80][81][82][83][84][85][86][87], octahedrally coordination d 0 -TM cations such as Ti 4+ , V 5+ , Mo 6+ , and the d 8 -TMO 4 square planar units into the metal iodate systems [117][118][119]. Our group has been working on metal iodates for many years and a number of NLO compounds based on metal iodates have been obtained by our group such as ␣-AgI 3 O 8 and ␤-AgI 3 O 8 (9.0 × KDP and 8.0 × KDP) [74], PbPt(IO 3 ) 6 (H 2 O) (8.0 × KDP) [87], [99], BaNbO(IO 3 ) 5 (14 × KDP) [105], etc.…”