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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) [(p‐C5H5NO)2ZnCl2] (1) and [p‐C5H6NO]2[ZnCl4] (2) were obtained by introducing the π‐conjugated p‐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. [ABSTRACT FROM AUTHOR]

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 Cs2Mg(NH2SO3)4 ⋅ 4H2O (1), as well as centrosymmetric K2Ca(NH2SO3)4 (2) and Rb2Ca(NH2SO3)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 [NH2SO3] 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 KH2PO4, 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. [ABSTRACT FROM AUTHOR]

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‐C5H4NSO3) ⋅ xH2O (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. [ABSTRACT FROM AUTHOR]

The approach of synergistically combining mixed chromophores has garnered significant attention attributed to its ability to leverage the advantages of both groups and design novel nonlinear optical (NLO) materials. Herein, Sr(NO3)(NH2SO3)·H2O, a noncentrosymmetric compound, which represents the first reported nitrate sulfamate compound, is successfully designed and synthesized. The compound features zigzag [SrNO10(H2O)]∞ infinite layers, forming a honeycomb‐like graphene topology in its layered structure. The unique arrangement results in an excellent second harmonic generation response, 5.1 times that of KH2PO4, and an optimized birefringence of 0.06650 at 532 nm. In addition, the presence of interlayered covalent [NH2SO3] groups facilitates improved crystal growth habits, resulting in a large single crystal measuring 19.0 × 17.0 × 3.5 mm3. In this discovery, a new class of NLO materials is introduced and the scope of structural chemistry is significantly expanded. [ABSTRACT FROM AUTHOR]

Exploring nonlinear optical crystals with large birefringence in the short‐wavelength ultraviolet (SWUV) regions (≤300 nm) is a valuable pursuit. Herein, KHC2O4·B(OH)3, which is composed of infinite [HC2O4]− and [B(OH)3] chains, was successfully grown via the slow evaporation method. The [HC2O4]− and [B(OH)3] chains endow KHC2O4·B(OH)3 with the largest birefringence (0.164@1064 nm) of all B(OH)3‐containing compounds that have been reported in the SWUV regions. Moreover, it possesses a moderate second‐harmonic generation response (0.3 × KH2PO4) and a short UV cutoff edge of 254 nm. The electron localization function diagram indicates the large birefringence originates from the HC2O4 and B(OH)3 groups. This work provides a new method to investigate crystals with large birefringence in the B(OH)3‐based oxalate system. [ABSTRACT FROM AUTHOR]

Discovering novel sulfate optical materials with strong second‐harmonic generation (SHG) and large birefringence is confronted by a great challenge attributed to the intrinsically weak polarizability and optical anisotropy of tetrahedral SO4 groups. Herein, two superior‐performing sulfate optical materials, namely, noncentrosymmetric Hg3O2SO4 and centrosymmetric CsHgClSO4 ⋅ H2O, have been successfully synthesized through the introduction of a highly polarizable d10 metal cation, Hg2+. The unique component layers in the reported compounds, [Hg3O2SO4]∞ layers in Hg3O2SO4 and [HgClSO4(H2O)]∞- layers in CsHgClSO4 ⋅ H2O, induce enlarged birefringence in each sulfate. Remarkably, Hg3O2SO4 exhibits a very large SHG response (14 times that of KH2PO4), which is the strongest efficiency among all the reported nonlinear optical sulfates. Detailed theoretical calculations confirm that the employment of highly polarizable Hg2+ is an effective strategy to design superior optical materials with large birefringence and strong SHG response. [ABSTRACT FROM AUTHOR]

NLO Materials. Deep‐ultraviolet transparent mixed metal sulfamates with enhanced nonlinear optical properties and birefringence are presented by Qun Jing, Kang Min Ok et al. in their Research Article (e202315434)...By Xuefei Wang; Xudong Leng; Yunseung Kuk; Jihyun Lee; Qun Jing and Kang Min OkReported by Author; Author; Author; Author; Author; Author [Extracted from the article]

Keywords: Birefringence; Optical Anisotropy; Sulfate Crystals; TetrahedraA design strategy for significantly enhancing the polarizability anisotropy of isotropic tetrahedra in sulfate crystals is reported by Zhiyong Bai and Kang Min Ok in their Research Article (e202315311). This strategy involves chemically alternating tetrahedral [SO4]2− units with π‐conjugated organic groups. Experimental validation of the approach utilized 3‐pyridinesulfonate anion functional building blocks for crystal synthesis...By Zhiyong Bai and Kang Min OkReported by Author; Author [Extracted from the article]

Keywords: Birefringence; Optical Anisotropy; Sulfate Crystals; TetrahedraA design strategy for significantly enhancing the polarizability anisotropy of isotropic tetrahedra in sulfate crystals is reported by Zhiyong Bai and Kang Min Ok in their Research Article (e202315311). This strategy involves chemically alternating tetrahedral [SO4]2− units with π‐conjugated organic groups. Experimental validation of the approach utilized 3‐pyridinesulfonate anion functional building blocks for crystal synthesis...By Zhiyong Bai and Kang Min OkReported by Author; Author [Extracted from the article]