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Trigonal planar units with large polarizability anisotropy and high physicochemical stability are ideal structural units for exploring nonlinear optical (NLO) materials. Integrating the merits of two types of triangular‐like moieties, a family of second‐order NLO‐active hybrid halides, MATX (X = Cl (1), Br (2), and I (3)), are achieved. MATX crystallizes in a nonpolar space group of P6¯$P\overline 6 $2c but exhibits the optimal spatial arrangement and superior NLO performance. The low coordination planar trigonal AgX3 units enable segregation in layers of the three‐winged propeller‐like Me3TPA units. All of the layers are packed in a perfect parallel fashion, making the functional materials exhibit superior NLO performances, including the phase matchable behavior with strong SHG responses (6.2/1, 6.5/2, and 7.6/3 times that of potassium dihydrogen phosphate), large birefringence (0.232/1, 0.252/2 and 0.260/3 at 1064 nm), high laser damage threshold, wide transparent window, and easiness of crystal growth. The first‐principles calculations reveal that the coexistence of strong linear and nonlinear optical properties are ascribed to the synergistic effect of the trigonal moieties. This study points out a useful path for the rational design of excellent NLO materials. [ABSTRACT FROM AUTHOR]

Thioborates are considered new potential mid-infrared nonlinear optical (NLO) crystals with wide band gaps and large second-harmonic generation (SHG) coefficients. Despite the fact that many rare-earth thioborates are structurally non-centrosymmetric, their SHG properties have only been studied very recently and their mid-infrared (Mid-IR) nonlinear optical properties have not yet been studied. In this work, we provide a new synthetic route for LaBS3 (LBS) by solid state reactions of La2S3, B and S with Li2S as flux, and we further study its thermal and optical properties, and theoretically explore the origin of its IR nonlinear optical properties by DFT calculations. Remarkably, LBS possesses balanced properties required for a good Mid-IR NLO crystal, a large SHG effect (1.2 × AgGaS2@2.05 μm – the largest among all known ortho-thioborates), a high laser induced-damage threshold (14 times of AgGaS2), a wide band gap (3.18 eV), a wide infrared transmission range (0.35–25 μm) and high thermal stability. Theoretical calculations suggest that its large SHG effect originates from the synergy effects of the π-conjugated [BS3]3− anions (41.82%) and the [LaS9]15− groups (58.18%). [ABSTRACT FROM AUTHOR]

The first NLO-active metal iodate-phosphates, namely, Cd2(IO3)(PO4) and Cd1.62Mg0.38(IO3)(PO4) (1 and 2), with three types of NLO groups, have been reported. 1 and 2 are isostructural and the structure of 1 features a 3D network formed by the Cd4(IO3)8/4(PO4)6/3 groups. 1 and 2 with strong SHG signals of 4 × and 3.5 × KH2PO4 are promising SHG materials in the visible region. [ABSTRACT FROM AUTHOR]

Three nonlinear optical materials Cd4REO(BO3)3 (RE = Sm, Eu, Tb) have been synthesized through high-temperature solid-state reactions. In their crystal structures, Cd(1)O8 and Cd(2)O6 polyhedra are interconnected via sharing edges and corners into a 3D anion framework with two types of tunnels based on 4- and 7-membered rings; the BO3 groups are grafted into the above-mentioned types, creating new tunnels based on Cd4B3 seven-membered rings, which are filled by RE3+ cations. Powder SHG measurements revealed that the Cd4REO(BO3)3 (RE = Sm, Eu, Tb) samples display SHG signals that are approximately 1.2, 5.6 and 1.5 times that of the KDP sample. In addition, Cd4EuO(BO3)3 and Cd4TbO(BO3)3 emit red and green light, respectively. The lifetime of the Eu(5D0) state for λex,em = 464, 610 nm in Cd4EuO(BO3)3 is measured to be about 1.43 ms whereas the lifetime of the Tb(5D4) state for λex,em = 376, 543 nm in Cd4TbO(BO3)3 is measured to be about 1.01 ms. [ABSTRACT FROM AUTHOR]

Through systematic experiments, two novel mercury iodate sulfates, namely, Hg2(IO3)2(SO4)(H2O) and Hg2(IO3)2(SO4) were obtained. They crystallize in monoclinic space group C2 and C2/c, respectively. Hg2(IO3)2(SO4)(H2O) exhibits the [Hg(IO3)]+ polar cationic layer inherited from Hg(IO3)2 and the three‐dimensional (3D) framework inherited from HgSO4. This enables Hg2(IO3)2(SO4)(H2O) to generate a strong second harmonic generation (SHG) response of 6 times that of KH2PO4 (KDP). The structure of Hg2(IO3)2(SO4) is very similar to that of Hg2(IO3)2(SO4)(H2O), and they can be transformed into each other. Hg2(IO3)2(SO4)(H2O) shows a large optical band gap of 3.98 eV and a high dehydration temperature of 250 °C. This study indicates that by reasonable design, the introduction of multiple functional groups into a compound may combine their advantages to achieve good overall optical performance. [ABSTRACT FROM AUTHOR]

An organic–inorganic hybrid polyiodate, namely, [o‐C5H4NHOH]2[I7O18(OH)]⋅3 H2O (I), featuring a novel branched polyiodate chain has been obtained by evaporation method. [o‐C5H4NHOH]2[I7O18(OH)]⋅3 H2O (I) crystalizes in the polar space group Ia and features an [I7O18(OH)]∞2- branched polyiodate chain in which [I3O9]3− trimers are grafted on the same side of the one‐dimensional (1D) chain based on [I4O11(OH)]3− tetramers. The asymmetric organic amine groups are beneficial to the polymerization of iodate groups and inducing the formation of the non‐centrosymmetric (NCS) structure. Compound I exhibits a rather large Second‐Harmonic‐ Generation (SHG) signal of 8.5×KH2PO4 (KDP) upon 1064 nm laser radiation, a moderate band gap of 3.90 eV and a high laser‐induced‐damage‐threshold (LIDT) of 182.34 MW cm−2, hence it is a promising new SHG material. The relationship between the structures of the organic amine groups and the overall structures has been also analyzed. [ABSTRACT FROM AUTHOR]

The introduction of coordination polyhedra containing stereo-chemically active lone pairs into the chalcogenide structures is beneficial for realizing centric-to-acentric structural transformation and further enhancing the second-harmonic generation (SHG) efficiency (dij) and the birefringence (Δn) for IR nonlinear optical (NLO) applications; however, this has been rarely reported. Herein, non-centrosymmetric (NCS) arsenates M2As2Q5 (M = Ba, Pb; Q = S, Se) have been screened out by combined experiments and theoretical calculations as a new source of IR NLO materials. Interestingly, they feature unique zero-dimensional structures containing diverse types of discrete As-based coordination polyhedra with M2+ cations located among them, which is discovered for the first time in the IR-NLO chalcogenides. More significantly, they all exhibit multiple key NLO parameters for practical applications in the IR region, including wide phase-matching ranges (>950–1370 nm), remarkable dij (1.0–2.7 × AgGaS2) and large laser-induced damage thresholds (LIDTs = 6.8–12.4 × AgGaS2). Theoretical studies demonstrate that the discrete As-based coordination polyhedra play a critical role in the linear optical and NLO responses of the title compounds. We believe that this work can not only enrich the diversity of NLO-active groups, but also provide a new choice for material design in NCS chalcogenides. [ABSTRACT FROM AUTHOR]

A novel mixed-anion NLO crystal, namely, Bi4O(I3O10)(IO3)3(SeO4), containing a brand-new "pinwheel-like" I3O105− polyiodate anion group was constructed from the trimeric condensation of IO43− monomers. Bi4O(I3O10)(IO3)3(SeO4) exhibits a complex 3D topological structure and gives a moderate second harmonic generation (SHG) signal about 1.1 times that of KH2PO4 (KDP). [ABSTRACT FROM AUTHOR]

The first alkali‐metal vanadium iodate fluoride, CsVO2F(IO3), with a novel 3D anionic framework, has been rationally designed and hydrothermally synthesized. The 3D [VO2F(IO3)]− framework in CsVO2F(IO3) is built from 0D Λ‐shaped cis‐[VO3F(IO3)2]4− polyanions via corner‐sharing of oxo anions and bridging of the iodate groups. CsVO2F(IO3) displays both a strong second‐harmonic generation (SHG) 1.1 times as strong as KTiOPO4 (KTP) under 2.05 μm laser radiation and high laser‐induced damage threshold (LIDT) of 107.9 MW cm−2. This work provides a new route to design SHG crystals with stable 3D anionic structures from low‐dimensional structural building units. [ABSTRACT FROM AUTHOR]

A large nonlinear optical (NLO) coefficient and a wide band gap are two crucial but contradictory parameters that are difficult to achieve simultaneously in a single infrared (IR) NLO compound. A salt‐inclusion chalcogenide (SIC), Li[LiCs2Cl][Ga3S6] (1), was prepared that presents a nanosized tunnel framework constructed from monotype chalcogenide tetrahedra. Highly oriented covalent GaS4 tetrahedra in the host lead to a moderate second harmonic generation response (0.7 AgGaS2), and ionic guests effectively broaden the band gap to the widest value (4.18 eV) among all IR NLO chalcogenides, thereby achieving a remarkable balance between NLO efficiency and band gap. [ABSTRACT FROM AUTHOR]

It is highly desirable but challenging to design and synthesize novel non-centrosymmetric (NCS) metal–organic frameworks (MOFs) with excellent nonlinear optical (NLO) properties. And the origin of their NLO responses remains vague. Herein, a novel 1D Zn-based MOF with unique zigzag helical chains, [Zn(bct)(H2O)2] (MOF-FJ1), has been prepared from achiral precursors. It crystallizes in an NCS space group P212121 (no. 19) and is found to be a remarkable NLO material with a strong second-harmonic-generation (SHG) response (3.5 × commercial KH2PO4 (KDP)) and high laser-induced damage threshold (1.6 × commercial KDP). Moreover, theoretical calculations based on the length-gauge formalism are discussed to unveil a deepened cognition of the structure–property relationship, providing theoretical insight into the origin of the NLO response. [ABSTRACT FROM AUTHOR]

New middle and far-infrared (MFIR) nonlinear optical (NLO) chalcogenides have been receiving increasing attention for their great importance in military and civil fields. In addition, the current challenge in the efforts for identifying a promising MFIR NLO material lies in achieving simultaneously large second-harmonic generation (SHG) intensity and high laser-induced damage threshold (LIDT) in the same material. In this study, two quaternary non-centrosymmetric (NCS) sulfides, BaAg2GeS4 (1) and BaAg2SnS4 (2), were synthesized from a high-temperature solid-state reaction using BaCl2 flux in evacuated closed silica tubes. Although 1 and 2 show identical stoichiometry, they crystallize in different NCS space groups, tetragonal I4̅2m (no. 121) and orthorhombic I222 (no. 23), respectively, based on the results of crystal structure solution. In their structures, highly distorted AgS4 tetrahedra interconnect together via corner-sharing to form two-dimensional (2D) layers, which are further bridged with isolated GeS4 or SnS4 units to produce a three-dimensional (3D) framework structure with Ba cations lying in the tunnels. Remarkably, they not only possess phase-matchable (PM) abilities but also exhibit a good balance between strong SHG responses (1.7× and 0.4× AgGaS2) and high LIDTs (3.2× and 1.5× AgGaS2). Moreover, theoretical calculations based on density functional theory (DFT) methods have aided the understanding of energy bands, electronic structures, and linear and NLO properties. [ABSTRACT FROM AUTHOR]

To develop new mid-infrared (MIR) nonlinear optical (NLO) materials, which can overcome the low laser damage threshold (LDT) of the commercial MIR-NLO crystals (AgGaS2, AgGaSe2 and ZnGeP2) and simultaneously keep the large NLO susceptibility, is necessary for high-power MIR laser frequency conversion technology. To improve the LDT, a new strategy of increasing lattice stability was adopted. Here, the strongly covalent structural unit of the PS4 tetrahedron was introduced into AgGaS2 (AGS), and that led to the isolation of the first compound in AgI-GaIII-PV-S system, namely, AgGa2PS6 ( Cc). It retains a large SHG efficiency (1.0×AGS) with phase-matchable ability, and also exhibits an improved LDT (5.1×AGS), indicating AgGa2PS6 is a new promising MIR-NLO crystal. Moreover, a novel 3D framework of [Ga2PS6]−, with triangular-shaped channels, as well as interesting single triangular geometry of AgS3-both of which are very rare in reported sulfides-was discovered in AgGa2PS6. Furthermore, theoretical calculations, and lattice energy and thermal expansions analyses suggest that the PS4 group makes a large contribution to the large SHG efficiency and high LDT. [ABSTRACT FROM AUTHOR]

Two new polar potassium gold iodates, namely, K2Au(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 K2Au(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 K2Au(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 K2Au(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. [ABSTRACT FROM AUTHOR]

Two new ternary rare earth chalcogenides, Dy3GaS6 (1) and Y3GaS6 (2), are reported here. They both crystallize in the orthorhombic space group Cmc21 (no. 36). Both are synthesized in pure phase and show phase-matchable second harmonic generation (SHG) of about 0.2 and 0.5 times, respectively for 1 and 2, as strong as that of KTiOPO4 (KTP) based on the powder SHG measurement at the wavelength of 1910 nm. They possess high powder laser induced damage thresholds (LIDTs), respectively, about 14 and 18 times that of AgGaS2 (AGS) based on the powder LIDT measurements under 1064 nm laser irradiation. They both exhibit wide transparency in the IR region (2.5–25 μm). It is believed that the title compounds are new candidates for nonlinear optical (NLO) materials in the IR region. To gain further insights into the NLO and LIDT properties of 1 and 2, the calculations of second-order NLO susceptibility and lattice energy density (LED) were also performed to explain their SHG efficiencies and high LIDTs. [ABSTRACT FROM AUTHOR]

The new compounds Ba3(BS3)1.5(MS3)0.5 (I) with M: Sb, Bi and Ba3(BQ3)(SbQ3) (II) with Q: S, Se are synthesized by solid state reaction of stoichiometric mixtures of the elements (graphite crucible in an evacuated silica tube, 820-920 °C). [ABSTRACT FROM AUTHOR]

New middle and far-infrared (MFIR) nonlinear optical (NLO) chalcogenides have been receiving increasing attention for their great importance in military and civil fields. In addition, the current challenge in the efforts for identifying a promising MFIR NLO material lies in achieving simultaneously large second-harmonic generation (SHG) intensity and high laser-induced damage threshold (LIDT) in the same material. In this study, two quaternary non-centrosymmetric (NCS) sulfides, BaAg2GeS4 (1) and BaAg2SnS4 (2), were synthesized from a high-temperature solid-state reaction using BaCl2 flux in evacuated closed silica tubes. Although 1 and 2 show identical stoichiometry, they crystallize in different NCS space groups, tetragonal I4̅2m (no. 121) and orthorhombic I222 (no. 23), respectively, based on the results of crystal structure solution. In their structures, highly distorted AgS4 tetrahedra interconnect together via corner-sharing to form two-dimensional (2D) layers, which are further bridged with isolated GeS4 or SnS4 units to produce a three-dimensional (3D) framework structure with Ba cations lying in the tunnels. Remarkably, they not only possess phase-matchable (PM) abilities but also exhibit a good balance between strong SHG responses (1.7× and 0.4× AgGaS2) and high LIDTs (3.2× and 1.5× AgGaS2). Moreover, theoretical calculations based on density functional theory (DFT) methods have aided the understanding of energy bands, electronic structures, and linear and NLO properties. [ABSTRACT FROM AUTHOR]

Exploring new material systems is a highly significant task in the field of inorganic chemistry. A new mixed-valent selenium compound, Hg 3 Se(SeO 3 )(SO 4 ), was successfully synthesized through in situ reactions. This compound exhibits a novel three-dimensional structure composed of Hg 3 Se(SO 4 ) layers bridged by SeO 3 trigonal pyramids. It is the first structure containing (SeO 3 ) 2- , (SO 4 ) 2- , and Se 2- simultaneously. In addition, Hg 3 Se(SeO 3 )(SO 4 ) possesses a wide bandgap (3.5 eV), moderate birefringence (Cal:0.064@546 nm, Exp:0.069@546 nm), a high laser-induced damage threshold (23.35 MW cm -2 ), and a wide transmittance window (0.28-6.6 μm). Our work demonstrates that mixed-valent (+4, -2) selenite selenide can be potential optical materials for the mid-infrared region.

Second-harmonic generation (SHG) response and birefringence are crucial properties for linear and nonlinear optical (NLO) materials, while it is difficult to further optimize these two key properties by using a single traditional functional building block (FBB) in one compound. Herein, a novel IO 4 5- unit is identified, which possesses a square-planar configuration and two stereochemically active lone-pairs (SCALPs). By combining IO 4 5- and IO 3 - units, the first examples of mixed-valent polyiodates featuring an unprecedented bowl-shaped I 5 O 12 - polymerized unit, namely (NH 4 ) 2 (I 5 O 12 )(IO 3 ) and K 1.03 (NH 4 ) 0.97 (I 5 O 12 )(IO 3 ), are successfully synthesized. Excitingly, both crystals exhibit strong SHG responses (16 × KDP and 19.5 × KDP @1064 nm) as well as giant birefringence (∆n exp  = 0.431 and 0.405 @546 nm). Detailed structure-property analyses reveal that the parallel aligned planar IO 4 5- units induce the properly aligned high-density SCALPs, leading to strong SHG response and giant birefringence for both materials. This work not only provides two new potential NLO and birefringent crystals, but also discovers a novel promising FBB (IO 4 5- ) for developing high-performance linear and nonlinear optical materials., (© 2023 Wiley-VCH GmbH.)

Two new mixed-anion cerium iodates, namely, Ce(IO 3 ) 3 F and Ce(IO 3 ) 2 (NO 3 ), have been rationally designed through the integration of hybrid anionic functional building blocks (FBBs). The structure of Ce(IO 3 ) 3 F features a novel [Ce(IO 3 ) 3 F] bilayer, and the material exhibits large birefringence (0.225 @546 nm). The structure of Ce(IO 3 ) 2 (NO 3 ) features [Ce 3 (IO 3 ) 6 ] 3+ triple layers that are further linked by planar NO 3 - units. Ce(IO 3 ) 2 (NO 3 ) shows a moderate SHG response (1 × KDP) and a high laser-induced damage threshold value (22 × AgGaS 2 ). This work demonstrates that the rich coordination geometries of cerium cations facilitate tuning of the structures of related compounds through modulating anionic FBBs.

Organic-inorganic hybrid nonlinear optical (NLO) materials are highly anticipated because of the integration of both merits of the organic and inorganic moieties. Herein, the 2-pyrimidinone cation (C 4 H 5 N 2 O) + has been incorporated into the iodate system to form two polymorphic organic-inorganic hybrid iodates, namely, α- and β-(C 4 H 5 N 2 O)(IO 3 )·HIO 3 . They crystallize in different polar space groups ( Ia and Pca 2 1 ), and their structures feature one-dimensional (1D) chain structures composed of (C 4 H 5 N 2 O) + cations, IO 3 - anions, and HIO 3 molecules interconnected via hydrogen bonds. α- and β-(C 4 H 5 N 2 O) (IO 3 )·HIO 3 exhibit strong and moderate second-harmonic-generation (SHG) responses of 6.4 and 0.9 × KH 2 PO 4 (KDP), respectively, the same band gaps of 3.65 eV, and high powder laser-induced damage threshold (LIDT) values [51 and 57 × AgGaS 2 (AGS)]. The results of theoretical calculations revealed that the large SHG effect of α-(C 4 H 5 N 2 O)(IO 3 )·HIO 3 originated from the IO 3 and HIO 3 groups. This work indicates that (C 4 H 5 N 2 O) + is a potential group for designing new NLO materials with brilliant optical performances.

Inorganic chalcogenides have been studied as the most promising infrared (IR) nonlinear optical (NLO) candidates for the past decades. However, it is proven difficult to discover high-performance materials that combine the often-incompatible properties of large energy gap (E g ) and strong second harmonic generation (SHG) response (d eff ), especially for rare-earth chalcogenides. Herein, centrosymmetric Cs 3 [Sb 3 O 6 ][Ge 2 O 7 ] is selected as a maternal structure and a new noncentrosymmetric rare-earth oxychalcogenide, namely, Nd 3 [Ga 3 O 3 S 3 ][Ge 2 O 7 ], is successfully designed and obtained by the module substitution strategy for the first time. Especially, Nd 3 [Ga 3 O 3 S 3 ][Ge 2 O 7 ] is the first case of breaking the trade-off relationship between wide E g (>3.5 eV) and large d eff (>0.5 × AgGaS 2 ) in rare-earth chalcogenide system, and thus displays an outstanding IR-NLO comprehensive performance. Detailed structure analyses and theoretical studies reveal that the NLO effect originates mainly from the cooperation of heteroanionic [GaO 2 S 2 ] and [NdO 2 S 6 ] asymmetric building blocks. This work not only presents an excellent rare-earth IR-NLO candidate, but also plays a crucial role in the rational structure design of other NLO materials in which both large E g and strong d eff are pursued., (© 2023 Wiley-VCH GmbH.)

A new polar hafnium iodate, CsHfF 4 (IO 3 ), was successfully designed and synthesized by integrating fluorinated hafnium-oxygen polyhedra (HfF 6 O 2 ) and IO 3 - anionic functional groups. Owing to the weak electronic effect of Hf 4+ and the bond-network-induced out-of-center distortion of the HfF 6 O 2 dodecahedra, CsHfF 4 (IO 3 ) achieves a good balance between a strong second-harmonic-generation effect (3.5 × KH 2 PO 4 ) and a rather large band gap (4.47 eV), which is the largest among the d 0 transition-metal iodates. In addition, CsHfF 4 (IO 3 ) possesses a wide transparent region (0.27-9.9 μm), a large birefringence for phase-matching (0.161), and a high laser-induced damage threshold (55.41 MW cm -2 , 26 × AgGaS 2 ) and is nonhygroscopic. This work indicates that the integration of mixed-ligand acentric coordination polyhedra and functional groups containing lone electron pairs is an effective strategy for developing novel inorganic nonlinear-optical materials with balanced overall properties.

Large-sized crystals of the quaternary iodate NaVO 2 (IO 3 ) 2 (H 2 O) (NVIO) with centimeter-scale dimensions (23 mm × 18 mm × 6 mm as a representative) have been successfully grown by the top-seeded hydrothermal method. Linear optical properties have been measured, including the optical transmission spectrum and refractive index. The NVIO crystal possesses an optical window with high transmittance (above 80%) over the range of 500-1410 nm and exhibits strong optical anisotropy with large birefringence Δ n ( n z - n x ) of 0.1522 at 1064 nm and 0.1720 at 532 nm. Based on the measured refractive indices, the phase-matching conditions for second-harmonic generation (SHG) have been calculated, and SHG devices have further been fabricated along the calculated type I and type II phase-matching directions of (θ = 39.0°, φ = 3.8°) and (θ =53.8°, φ = 1.3°). Laser experiments of extra-cavity frequency doubling have been performed on these NVIO devices. It has been confirmed that the effective SHG conversion from 1064 to 532 nm could be achieved with an energy conversion efficiency of 8.1%. Our work demonstrates that large-sized NVIO crystals are promising in the frequency-doubling application.