HBa_2.5(IO₃)₆(I₂O₅) and HBa(IO₃)(I₄O₁₁): Explorations of Second-Order Nonlinear Optical Materials in the Alkali-Earth Polyiodate System

Abstract

Two new barium polyiodate compounds in the alkali-earth system, namely, HBa2.5(IO3)6(I2O5) (Fdd2) and HBa­(IO3)­(I4O11) (P1̅) have been obtained through hydrothermal reaction. Interestingly, the structures of both compounds feature different polyiodate groups, i.e., I2O5 and I4O11 groups. HBa2.5(IO3)6(I2O5) can be depicted as an alternative stacking of two-dimensional (2D) [Ba4(IO3)8(I2O5)2] and [Ba­(IO3)4(I2O5)2]2– layers with the I2O5 and IO3 group serving as linkers. HBa­(IO3)­(I4O11) can be depicted as a 3D network with 2D [Ba­(I4O11)] layers being interconnected by IO3 groups. The 0D I4O11 polyiodate group can be seen also viewed as formed by an I3O8 group further corner-sharing with an IO3 group or an I2O5 group further corner-sharing with two IO3 groups. Powder second harmonic generation (SHG) measurements show that HBa2.5(IO3)6(I2O5) crystals display a moderate SHG efficiency of ∼1.6 times that of KH2PO4 (KDP) and are phase-matchable. Optical properties measurements, thermal analyses, and laser damage threshold (LDT) measurements have been performed. Results of theoretical calculation show that the formation of I4O11 2– is thermodynamically much easier than I3O8 – and I2O5, because of the lower reaction energy. Our studies shed light on exploring alkali-earth polyiodates as potential NLO materials.

REI5O14 (RE=Y and Gd): Promising SHG Materials Featuring the Semicircle‐Shaped I5O143− Polyiodate Anion

“…The I 5 O 14 pentamer could be viewed as an I 3 O 8 unit corner‐sharing with two additional IO 3 groups (one on each end). This condensation fashion is consistent with other polyiodate anions (IO 3 ‐IO 4 ‐IO 3 for I 3 O 8 ; and IO 3 ‐IO 4 ‐IO 4 ‐IO 3 for I 4 O 11 ) (Scheme ) . Herein, the elongated I−O bonds (2.428 (8) Å in YI 5 O 14 and 2.423 (18) Å in GdI 5 O 14 ) linking I 3 O 8 and IO 3 were assigned into intra‐molecular bonds, for the reason that the oxidation state of I(2a) should be close to +5 (Tables S2–S3) .…”

“…The isolated I 4 O 11 2− anion is only observed in HBa(IO 3 )(I 4 O 11 ) . During the preparation of HBa(IO 3 )(I 4 O 11 ), phosphoric acid played an important role, probably owing to the fact that the consistency of the reaction media was strengthened by H 3 PO 4 . To the best of our knowledge, the study of metal polyiodates only involves the alkali metal or Ag + and Ba 2+ iodate systems.…”

“…For example, the introduction of the strongly distorted d 0 ‐TM polyhedron (e.g., TiO 6 , VO 5 , VO 6 , VO 4 F 2 , NbO 6 , and MoO 6 ) or stereo‐chemical‐active lone‐pair (SCALP) bismuth (III) oxide or fluoride frameworks (e.g., , ) into iodates have largely guided the discovery of many novel and excellent SHG materials. On the other hand, the iodate units, IO x ( x= 3 and 4), are able to be condensed into new SHG‐active groups . Some monovalent metal polyiodates have been reported to display very strong SHG effects, such as α‐Cs 2 I 4 O 11 (400×SiO 2 ), NaI 3 O 8 (300×α‐SiO 2 ), and α‐ and β‐AgI 3 O 8 (9×KDP) .…”

From Ag2Zr(IO3)6 to LaZr(IO3)5F2: A Case of Constructing Wide‐band‐gap Birefringent Materials through Chemical Cosubstitution

“…So far, the introduction of other SOJT distortive cations (V 5+ , Nb 5+ , Bi 3+ , Pb 2+ , etc .) into metal iodates or condensation of IO 3 − and IO 4 3− anions to form polyiodate anions are the two major routes for exploring new metal iodates, which have led to the discovery of many metal iodates with excellent SHG performance [12–33] …”

[o‐C5H4NHOH]2[I7O18(OH)]⋅3 H2O: An Organic–Inorganic Hybrid SHG Material Featuring an [I7O18(OH)] Branched Polyiodate Chain

“…enhance the SHG effects, such as Bi(IO 3 )F 2 (11.5 KDP), aand b-Ba 2 [GaF 4 (IO 3 ) 2 ](IO 3 ) (6 KDP); [15,16] (d) Combination of IO 3 À and the delocalized p-conjugated groups such as nitrate and carbonate as in Sc(IO 3 ) 2 (NO 3 ) (4 KDP); [17] and (e) Condensation of IO x (x = 3 and 4) into polyiodates with strong SHG effects exampled by NaI 3 O 8 (300 SiO 2 ) and REI 5 O 14 (RE = Y and Gd) (14 and 15 KDP). [18][19][20][21][22][23][24] At present, only a few polyiodates exhibiting strong SHG effects have been reported, such as NaI 3 O 8 (300 SiO 2 ), [18] aand b-AgI 3 O 8 (9 and 8 KDP), [20] a-Cs 2 I 4 O 11 (300 SiO 2 ), [23] and REI 5 O 14 (RE = Y and Gd) (14 and 15 KDP). [24] It is believed that the condensation of IO x (x = 3 and 4) may enhance the densities of SHG active iodate groups per unit cell, hence it has a significant impact on the structures and SHG capabilities of the polyiodates formed.…”