Bi(SO4)F·H2O and Bi(SO4)(NO3)·3H2O: Chemical Substitution-Induced Birefringence Enhancement in Bismuth Sulfates.

Two new Bi(III)-based sulfates, namely, Bi(SO4)F·H2O (BSOF) and Bi(SO4)(NO3)·3H2O (BSNO), have been successfully synthesized through aliovalent replacement of partial [SO4]2- groups with F- and [NO3]- anions, respectively, in the parent structure of Bi2(SO4)3. Such chemical replacement altered the coordination environment of Bi3+ cations, facilitating changes in the structure and optical properties. Notably, the birefringence values of BSOF and BSNO are found to be 4.4 and 15.5 times that of parent Bi2(SO4)3. Further investigation into the structure-property relationship revealed that the birefringence enhancement in BSOF and BSNO is attributed to the improvement of the polarizability anisotropy of Bi3+-centered polyhedra in BSOF and BSNO compared to that of Bi2(SO4)3. In addition, the existence and optimized arrangement of planar [NO3]- groups are also indispensable for further birefringence improvement of the BSNO compound.

Crystal clear: unveiling giant birefringence in organic-inorganic cocrystals.

Coplanar groups with large anisotropic polarizability are suitable as birefringence-active groups for investigating compounds with significant birefringence. In this study, the organic coplanar raw reagent, o-C5H5NO (4HP), was selected as an individual complement. Utilizing the cocrystal engineering strategy, we successfully designed two cocrystals: [LiNO3·H2O·4HP]·4HP (Li-4HP2) and [Mg(NO3)2·6H2O]·(4HP)2 (Mg-4HP), and one by-product: LiNO3·H2O·4HP (Li-4HP), which were grown using a mild aqua-solution method. The synergy of the coplanar groups of NO3 - and 4HP in the structures resulted in unexpectedly large birefringence values of 0.376-0.522@546 nm. Furthermore, the compounds exhibit large bandgaps (4.08-4.51 eV), short UV cutoff edges (275-278 nm), and favorable growth habits, suggesting their potential as short-wave UV birefringent materials.

Correction: Hydrogen bonding bolstered head-to-tail ligation of functional chromophores in a 0D SbF3·glycine adduct for a short-wave ultraviolet nonlinear optical material.

[This corrects the article DOI: 10.1039/D4SC01353K.].

Breaking Boundaries: Giant Ultraviolet Birefringence in Dimension-Reduced Zn-Based Crystals.

Birefringent crystals have essential applications in optical communication areas. Low-dimensional structures with inherited structural anisotropy are potential systems for investigating birefringent materials with large birefringence. In this work, the zero-dimensional (0D) [(o-C5H5NO)2ZnCl2] (1) and [o-C5H6NO]2[ZnCl4] (2) were obtained by introducing the π-conjugated o-C5H5NO (4HP) into the three-dimensional (3D) ZnCl2. Remarkably, 1 exhibits a giant birefringence of 0.482@546 nm, which is the largest among Zn-based ultraviolet (UV) compounds and 160 times that of ZnCl2. According to structural and theoretical calculation analyses, the large optical polarizability, high spatial density, ideal distribution of the [(4HP)2ZnCl2]0 cluster, and the low dimension of 1 result in the dramatically increased birefringence compared to ZnCl2. This work will provide a valid route for accelerating the design and synthesis of compounds with excellent birefringence in low-dimensional systems.

Hydrogen bonding bolstered head-to-tail ligation of functional chromophores in a 0D SbF3·glycine adduct for a short-wave ultraviolet nonlinear optical material.

The key properties of nonlinear optical (NLO) materials highly rely on the quality of functional chromophores (FCs) and their optimized interarrangement in the lattice. Despite the screening of various FCs, significant challenges persist in optimizing their arrangement within specific structures. Generally, FC alignment is achieved by designing negatively charged 2D layers or 3D frameworks, further regulated by templating cations. In this study, a novel 0D adduct NLO material, SbF3·glycine, is reported. Neutrally charged 0D [SbF3C2H5NO2] FCs, comprising [SbF3] pyramids and zwitterionic glycine, are well-aligned in the structure. The alignment is facilitated by the hydrogen bonding, reinforcing a 'head-to-tail' ligation of [SbF3C2H5NO2] FCs. Consequently, the title compound exhibits favorable NLO properties, including a large second-harmonic generation efficiency (3.6 × KDP) and suitable birefringence (cal. 0.057 @ 1064 nm). Additionally, its short absorption cut-off edge (231 nm) positions it as a promising short-wave ultraviolet NLO material. Importantly, the binary SbF3-amino acid system is expected to serve as a new resource for exploring ultraviolet NLO crystals, owing to the abundance of the amino acid family.

Guanidinium Vanadate [C(NH2)3]3VO4·2H2O Revealing Enhanced Second-Harmonic Generation and Wide Band Gaps.

A new guanidinium-templated vanadate, [C(NH2)3]3VO4·2H2O, has been synthesized in a phase-pure form. It crystallizes in a noncentrosymmetric polar space group, Cc, and the crystal structure is built upon a framework of guanidinium, vanadate tetrahedra, and water molecules linked by hydrogen bonds. Notably, optical measurements reveal that the material exhibits an approximately 9.6-fold enhancement in second-harmonic generation efficiency compared to its phosphate analogue. The enhancement can be attributed to the increased geometrical distortion of the VO4 tetrahedra. Furthermore, we found that the coordination number of the central vanadium atom significantly affects the optical band gaps. Among various coordination numbers, the 4-coordinate VO4 tetrahedra are found to be more favorable for widening the optical band gap of materials compared to the 5- and 6-coordinate vanadium polyhedra, as demonstrated by this work.

Exceptional Optical Anisotropy Enhancement Achieved Through Dual-Ions Cosubstitution Strategy in Novel Hybrid Bismuth Halides.

Guided by a superb dual-ions cosubstitution strategy, two novel, highly optically anisotropic hybrid bismuth halides are designed and synthesized. The first compound, Gu3Bi2NO3Cl8 (Gu = C(NH2)3), is developed using the 2D perovskite halide Cs3Bi2Cl9 as the maternal structure. This involved substituting all Cs+ cations with organic Gu+ and replacing some Cl- anions with [NO3]-. Further substitution of Cl- with additional [NO3]- resulted in the formation of nitrate-rich Gu2Bi(NO3)3Cl2 crystal, exhibiting a 3.4-fold increase in [NO3]- per unit volume. Both compounds have a structurally 0D nature, comprising bismuth-centered polyhedra formed by coordinated chlorides and monodentate/bidentate nitrate moieties, with Gu+ serving as a separator and linker. Notably, the presence of superb optically anisotropic dual-ions, i.e., planar Gu+ and [NO3]-, enables these crystals to possess sharply enhanced optical anisotropy, with birefringence values more than 1 order of magnitude higher than that of the initial crystal Cs3Bi2Cl9 (0.162/0.186vs 0.011 at 546 nm). The discovery and characterization of Gu3Bi2NO3Cl8 and Gu2Bi(NO3)3Cl2 crystals provide new insights into achieving expected modifications in optical properties through the utilization of a dual-ions cosubstitution strategy.

Designing Optical Anisotropy: Silver-Aminoalkylpyridine Nitrate Complexes with Tunable Structures.

To introduce a design strategy for improving optical properties, two silver-amino alkylpyridine nitrate complexes, AgC6H8N3O3 and Ag2C14H20N6O6, were successfully synthesized using a recrystallization method. By employing polarizable π-conjugated [NO3-] ions, two types of pyridine ligands, and silver cations with a high affinity for pyridine, we obtained a one-dimensional chain structure with 4-aminomethylpyridine (AgC6H8N3O3) and a zero-dimensional molecular compound by introducing a relatively flexible aliphatic chain with 4-(2-aminoethyl)pyridine (Ag2C14H20N6O6). The compounds crystallize in the triclinic crystal system with the centrosymmetric P-1 space group, exhibiting a change in orientation between the π-conjugated system and the silver ion. Despite similar optical band gaps (3.69 eV for AgC6H8N3O3 and 3.73 eV for Ag2C14H20N6O6), AgC6H8N3O3 shows higher absorption in the 350-600 nm range. Electronic structure calculations support the ultraviolet absorption findings, suggesting that charge transfer with π-conjugated systems influences birefringence. Ag2C14H20N6O6 exhibits experimental birefringence (0.261@546.1 nm) surpassing that of AgC6H8N3O3 (0.212@546.1 nm), placing it among the highest recorded values within metal-pyridine incorporating nitrate complexes. The nonconventional orientation of π-conjugated [NO3-] ions contributes to this phenomenon, enhancing the action of free π-conjugated orbitals. This design strategy for micromodulating the alignment of the π-conjugated system promises to be an effective approach for enhancing optical properties, such as birefringence.

Deep-Ultraviolet Transparent Mixed Metal Sulfamates with Enhanced Nonlinear Optical Properties and Birefringence.

Enhancing anisotropy through the controlled arrangement of anionic groups is essential for improving the nonlinear optical (NLO) performance of non-π-conjugated NLO materials. In this study, we present the successful synthesis of the first examples of mixed alkali metal-alkaline earth metal sulfamate materials, including noncentrosymmetric Cs2 Mg(NH2 SO3 )4 ⋅ 4H2 O (1), as well as centrosymmetric K2 Ca(NH2 SO3 )4 (2) and Rb2 Ca(NH2 SO3 )4 (3). All three compounds feature promising deep ultraviolet cut-off edges, notably 1 with a cut-off edge below 180 nm. The synergy of Cs+ and Mg2+ cations in 1 facilitated the successful alignment of polar [NH2 SO3 ] tetrahedra in a uniform orientation. Remarkably, 1 stands as the sole instance among reported sulfamate compounds with a co-parallel anionic arrangement, yielding a very large dipole moment compared to other non-π-conjugated NLO materials. Moreover, the substantial dipole moment of 1 yields an enhanced second harmonic generation response, approximately 2.3 times that of KH2 PO4 , and a large birefringence of 0.054 at 546.1 nm. The approach of regulating the arrangement of anionic groups using aliovalent cations holds promise for advancing the exploration of non-π-conjugated NLO materials.

Designing Sulfate Crystals with Strong Optical Anisotropy through π-Conjugated Tailoring.

Sulfate crystals typically exhibit minimal optical anisotropy due to the near-zero polarizability anisotropy (δ) of [SO4 ]2- tetrahedra, arising from highly symmetrical electron clouds. Recent research sought to enhance δ via chemical modifications, such as fluorination. However, the resultant crystals often maintain subpar optical anisotropy, frequently with birefringence values below 0.1. In this study, we have uncovered that δ can be significantly strengthened by chemically tailoring the tetrahedral [SO4 ]2- with anisotropic π-conjugated modules. This has been demonstrated by several newly proposed S-O-Org (Org: π-conjugated organic species) moieties, which show a sharp increase in δ based on theoretical computations. To further validate this experimentally, we synthesized and characterized six new 3-pyridinesulfonate crystals with the formula A(3-C5 H4 NSO3 ) ⋅ xH2 O (A=Li, Ag, K, Rb, Cs, and NH4 ; x=0 and 1). Notably, these materials exhibit strong optical anisotropy, with birefringence values ranging from 0.240 to 0.312 at 546 nm. These values are approximately 23 to 145.5 times greater than those of corresponding sulfates, and they outperform a vast number of sulfate-related optical materials, thus verifying the effectiveness of the proposed strategy. Furthermore, the title compounds exhibit diverse microstructure peculiarities influenced by the size and binding natures of the counter cations.

Chiral amino acid-templated tin fluorides tailoring nonlinear optical properties, birefringence, and photoluminescence.

In this study, we successfully synthesized two types of new chiral amino acid-templated tin fluoride crystals: (R)-[(C8H10NO3)2]Sn(IV)F6, (S)-[(C8H10NO3)2]Sn(IV)F6, (R)-[C8H10NO3]Sn(II)F3, and (S)-[C8H10NO3]Sn(II)F3, employing a slow evaporation method. The crystal structures of Sn(IV)-compounds were determined to belong to the noncentrosymmetric (NCS) nonpolar space group, P21212. Conversely, the structures of Sn(II)-compounds were found to crystallize in the NCS polar space group, P21, as revealed by single-crystal X-ray diffraction analysis. Remarkably, Sn(IV)-compounds exhibited a larger birefringence (0.328@546.1 nm), attributed to the well-stacked arrangement of planar π-conjugated benzene rings along the b-axis. The ability of tin(IV) fluorides to form more hydrogen bonds with ligands increased the probability of π-π interactions between benzene rings, enabling the growth of centimeter-sized crystals in Sn(IV)-compounds. In contrast, Sn(II)-compounds displayed a stronger second-harmonic generation (SHG) response (0.85 × KDP) than Sn(IV)-compounds (0.46 × KDP). This enhanced SHG response in Sn(II)-compounds was attributed to the increased dipole moments resulting from the presence of lone pairs. Additionally, Sn(II)-compounds exhibited photoluminescent properties due to the transition from the metal-to-ligand charge transfer state, facilitated by the presence of the lone pairs.

Multifunctional Chiral d10 -Metal Coordination Polymers: Tunable Photoluminescence and Efficient Second-Harmonic Generation with Circular Dichroic Response.

A series of homochiral coordination polymers (HCPs), [M2 (SIAP)2 (bpy)2 ] [M(S)] and [M2 (RIAP)2 (bpy)2 ] [M(R)] (M = Zn or Cd, SIAP or RIAP = (S,S)- or (R,R)- 2,2'-(isophthaloylbis(azanediyl))di-propionic acid, bpy = 4,4'-bipyridine), is successfully synthesized through solvothermal reactions, self-assembling d10 metal cations, chiral dicarboxylic ligands, and π-conjugated bipyridyl ligands. The HCPs crystallize in the extremely rare triclinic chiral space group, P1, and present 3D framework structures attributed to the strong intermolecular interactions, such as hydrogen bonds and π-π stacking. Due to the unique crystal structures, the title compounds reveal efficient photoluminescence emission across a broad visible range, with significant brightness and color tuning by varying the excitation wavelength. Moreover, they exhibit efficient phase-matched second-harmonic generation (SHG) with very high laser-induced damage thresholds, essential for high-power nonlinear optical (NLO) applications. Intriguingly, the title compounds exhibit a measurable contrast in the SHG response under right- and left-handed circularly polarized excitation, thereby providing a unique case of SHG circular dichroism from the chiral centers of SIAP2- or RIAP2- ligand packed in the noncentrosymmetric environment. These exceptional attributes position these HCPs as promising candidates for multifunctional materials, with potential applications ranging from NLO devices to tailored luminescent systems with polarization control.

Cu(I)-thioether coordination complexes based on a chiral cyclic ß-amino acid ligand.

Coordination complexes, particularly metalloproteins, highlight the significance of metal-sulfur bonds in biological processes. Their unique attributes inspire efforts to synthetically reproduce these intricate metal-sulfur motifs. Here, we investigate the synthesis and characterization of copper(I)-thioether coordination complexes derived from copper(I) halides and the chiral cyclic ß-amino acid trans-4-aminotetrahydrothiophene-3-carboxylic acid (ATTC), which present distinctive structural properties and ligand-to-metal ratios. By incorporating ATTC as the ligand, we generated complexes that feature a unique chiral conformation and the capacity for hydrogen bonding, facilitating the formation of distinct geometric structures. Through spectroscopic analyses and density functional theory (DFT) calculations, we studied the complexes' optical properties, including their emission bands and variable second-harmonic generation (SHG) efficiencies, which vary based on the halide used. Our findings underscore the potential of the ATTC ligand in creating unusual coordination complexes and pave the way for further investigations into their potential applications, particularly within materials science.

Synthesis and Anti-Inflammatory Activity of N(2)-Arylindazol-3(2H)-One Derivatives: Copper-Promoted Direct N-Arylation via Chan-Evans-Lam Coupling.

Inflammatory-related diseases are becoming increasingly prevalent, leading to a growing focus on the development of anti-inflammatory agents, with a particular emphasis on creating novel structural compounds. In this study, we present a highly efficient synthetic method for direct N-arylation to produce a variety of N(2)-arylindazol-3(2H)-ones 3, which exhibit anti-inflammatory activity. The Chan-Evans-Lam (CEL) coupling of N(1)-benzyl-indazol-3-(2H)-ones 1 with arylboronic acids 2 in the presence of a copper complex provided the corresponding N(2)-arylindazol-3(2H)-ones 3 in good-to-excellent yields, as identified with NMR, MS, and X-ray crystallography techniques. The cell viability and anti-inflammatory effects of the synthesized compounds (3 and 5) were briefly assessed using the MTT method and Griess assay. Among them, compounds 5 exhibited significant anti-inflammatory effects with negligible cell toxicity.

Green and Red Photoluminescent Manganese Bromides with Aminomethylpyridine Isomers.

Two positional isomers, 4-amino-3-methylpyridine and 3-amino-5-methylpyridine, produce 4-amino-3-methylpyridinium and 5-methylpyridin-3-aminium, respectively, under acidic conditions. The two protonated isomers create different hydrogen bonding networks, resulting in different coordination environments of the [MnX4]2- unit embedded in molecular compounds such as 4-amino-3-methylpyridinium manganese bromide, [(C6H9N2)2MnBr4] and 5-methylpyridin-3-aminium manganese bromide, [(C6H9N2)4MnBr4(H2O)·(MnBr4)]. Both compounds can be prepared using the slow evaporation method or mechanochemical synthetic procedures. Single-crystal structure analysis of [(C6H9N2)2MnBr4] and [(C6H9N2)4MnBr4(H2O)·(MnBr4)] revealed different manganese halide units, including tetrahedral and tetrahedral with distorted trigonal bipyramidal structures, which emit photoluminescence in the green (527 nm) and red (607 nm) regions, respectively. Electronic structure calculations were conducted to support the validity and interpretation of the UV-vis and photoluminescence (PL) spectral data. Thin films deposited using the [(C6H9N2)2MnBr4] precursor also exhibit PL properties. The diverse pseudo-three-dimensional networks can be constructed by using positional isomers with different hydrogen bonding pathways and π-π stacking of organic units, in which the design strategy successfully enables the tuning of various optical properties.

Yb Substitution and Ultralow Thermal Conductivity of the Ca3-xYbxAlSb3 (0 ≤ x ≤ 0.81(1)) System.

A series of Yb-substituted Zintl phases in the Ca3-xYbxAlSb3 (0 ≤ x ≤ 0.81(1)) system has been synthesized by initial arc melting and post-heat treatment, and their isotypic crystal structures were characterized by both powder and single crystal X-ray diffraction analysis. All four title compounds adopted the Ca3AlAs3-type structure (space group Pnma, Pearson code oP28, Z = 4). The overall structure can be described as a combination of the 1-dimensional (1D) infinite chain of ∞1[Al(Sb2Sb2/2)] formed by two vertices sharing [AlSb4] tetrahedral moieties and three Ca2+/Yb2+ mixed sites located in between these 1D chains. The charge balance and the resultant independency of the 1D chains in the title system were explained by the Zintl-Klemm formalism [Ca2+/Yb2+]3[(4b-Al1-)(1b-Sb2-)2(2b-Sb1-)2/2]. A series of DFT calculations proved that (1) the band overlap between the d-orbital states from two types of cations and the p-orbital states from Sb at the high symmetry Γ point implied a heavily doped degenerate semiconducting behavior of the quaternary Ca2YbAlSb3 model and (2) the site preference of Yb for the M1 site was due to the electronic-factor criterion based on the Q values of each atomic site. The electron localization function calculations also proved that the two different shapes of lone pairs of the Sb atoms─the "umbrella-shape" and the "C-shape"─are determined by local geometry and the coordination environment on the anionic frameworks. Thermoelectric measurements of the quaternary title compound Ca2.19(1)Yb0.81AlSb3 showed an approximately two times larger ZT value than that of ternary Ca3AlSb3 at 623 K due to increased electrical conductivity and ultralow thermal conductivity originated from Yb substitution for Ca.

Cd2 Nb2 Te4 O15 : A Novel Pseudo-Aurivillius-Type Tellurite with Unprecedented Nonlinear Optical Properties and Excellent Stability.

Oxides are emerging candidates for mid-infrared (mid-IR) nonlinear optical (NLO) materials. However, their intrinsically weak second harmonic generation (SHG) effects hinder their further development. A major design challenge is to increase the nonlinear coefficient while maintaining the broad mid-IR transmission and high laser-induced damage threshold (LIDT) of the oxides. In this study, it is reported on a polar NLO tellurite, Cd2 Nb2 Te4 O15 (CNTO), featuring a pseudo-Aurivillius-type perovskite layered structure composed of three types of NLO active groups, including CdO6 octahedra, NbO6 octahedra, and TeO4 seesaws. The uniform orientation of the distorted units induces a giant SHG response that is ≈31 times larger than that of KH2 PO4 , the largest value among all reported metal tellurites. Additionally, CNTO exhibits a large band gap (3.75 eV), a wide optical transparency window (0.33-14.5 µm), superior birefringence (0.12@ 546 nm), high LIDT (23 × AgGaS2 ), and strong acid and alkali resistance, indicating its potential as a promising mid-IR NLO material.

A Polar Tetragonal Tungsten Bronze with Colossal Second-Harmonic Generation.

A polar tetragonal tungsten bronze, Pb1.91 K3.22 □0.85 Li2.96 Nb10 O30 (□: vacancies), has been successfully synthesized by a high temperature solid-state reaction. Single crystal and powder X-ray diffraction indicate that the structure of Pb1.91 K3.22 □0.85 Li2.96 Nb10 O30 crystallizing in the noncentrosymmetric (NCS) space group, P4bm, consists of 3D framework with highly distorted NbO6 , LiO9 , PbO12 , and (Pb/K)O15 polyhedra. While NCS Pb1.91 K3.22 □0.85 Li2.96 Nb10 O30 undergoes a reversible phase transition between polar (P4bm) and nonpolar (P4/mbm) structure at around 460 °C, the material decomposes to centrosymmetric Pb1.45 K3.56 Li3.54 Nb10 O30 (P4/mbm) once heated to 1200 °C. Powder second-harmonic generation (SHG) measurements with 1064 nm radiation indicate that Pb1.91 K3.22 □0.85 Li2.96 Nb10 O30 exhibits a giant phase-matchable SHG intensity of ≈71.5 times that of KH2 PO4 , which is the strongest intensity in the visible range among all nonlinear optical materials reported to date. The observed colossal SHG should be attributable to the synergistic effect of dipole moments from the well-aligned NbO6 octahedra, the constituting distortive channels with vacancies, and highly polarizable cations.

DFT-Based Study for the Enhancement of CO2 Adsorption on Metal-Doped Nitrogen-Enriched Polytriazines.

Nitrogen-enriched polytriazine (NPT), a carbon nitride-based material, has received much attention for CO2 storage applications. However, to enhance the CO2 uptake capacity more efficiently, it is necessary to understand the interaction mechanism between CO2 molecules and NPT through appropriate modification of the structures. Here, we introduce a method to enhance the CO2 adsorption capacity of NPT by incorporating metal atoms such as Sn, Co, and Ni into the polytriazine network. DFT calculations were used to investigate the CO2 adsorption mechanism of the polytriazine frameworks by tracking the interactions between CO2 and the various interaction sites of NPT. By optimizing the geometry of the pure and metal-containing NPT frameworks, we calculated the binding energy of metal atoms in the NPT framework, the adsorption energy of CO2 molecules, and the charge transfer between CO2 molecules and the corresponding adsorption systems. In this work, we demonstrate that the CO2 adsorption capacity of NPT can be greatly enhanced by doping transition-metal atoms into the cavities of NPT.

Unveiling the Superior Optical Properties of Novel Melamine-Based Nonlinear Optical Material with Strong Second-Harmonic Generation and Giant Optical Anisotropy.

Two melamine-based metal halides, (C3 N6 H7 )(C3 N6 H6 )HgCl3 (I) and (C3 N6 H7 )3 HgCl5 (II), are synthesized by incorporating the heavy d10 cation, Hg2+ , and the halide anion, Cl- . The noncentrosymmetric structure of I results from two unique attributes: large asymmetric secondary building units produced by direct covalent coordination of melamine to Hg2+ and a small dihedral angle between melamine molecules. The former makes inorganic modules locally acentric, while the latter prevents planar organic groups from forming deleterious antiparallel arrangement. The unique coordination in I results in an enlarged band gap of 4.40 eV. Due to the large polarizability of the heavy Hg2+ cation and the π-conjugated system of melamine, I exhibits a strong second-harmonic generation efficiency of 5 × KH2 PO4 , larger than any reported melamine-based nonlinear optical materials to date. Density functional theory calculations indicate that I possesses giant optical anisotropy, with a birefringence of 0.246@1064 nm.