Chen Xinglong, Ok Kang Min
Department of Chemistry, Sogang University 35 Baekbeom-ro, Mapo-gu Seoul 04107 Korea
Chem Sci. 2022 Mar 15;13(14):3942-3956. doi: 10.1039/d1sc07121a. eCollection 2022 Apr 6.
Second-order nonlinear optical (NLO) materials have drawn enormous academic and technological attention attributable to their indispensable role in laser frequency conversion and other greatly facilitated applications. The exploration of new NLO materials with high performances thus has long been an intriguing research field for chemists and material scientists. However, an ideal NLO material should simultaneously satisfy quite a few fundamental yet rigorous criteria including a noncentrosymmetric structure, large NLO coefficients, desired transparent range, large birefringence, high laser damage threshold, and availability of a large-size single crystal. Therefore, the identification of promising compound systems, targeted design, and experience-based syntheses are crucial to discover novel NLO materials working in the spectral region of interest. As an important family of mixed-anion compounds, versatile metal oxyhalides containing metal-centered oxyhalide functional units ([MO X ] (X = F, Cl, Br, and I)) are becoming a marvelous branch for interesting NLO materials. Especially, when the central metals are d/d transition metals or heavy post-transition metals, a number of novel NLO materials with superior functionalities are expected. Our thorough review on the recent achievements of metal oxyhalides for NLO materials are divided into the fast-growing NLO metal oxyhalides with single type halogen anions and the newly identified NLO metal oxyhalides with mixed halogen anions. Here we mainly focus on the design strategy, structural chemistry, NLO-related properties, and structure-property correlation of the metal oxyhalides with relatively large NLO responses. We hope this review can provide an insight on the rational design and future development of emerging metal oxyhalides for NLO and other applications.
二阶非线性光学（NLO）材料因其在激光频率转换及其他诸多便利应用中不可或缺的作用而备受学术界和技术领域的广泛关注。因此，探索具有高性能的新型NLO材料长期以来一直是化学家和材料科学家们感兴趣的研究领域。然而，理想的NLO材料应同时满足一些基本但严格的标准，包括非中心对称结构、大的NLO系数、所需的透明范围、大的双折射、高的激光损伤阈值以及大尺寸单晶的可得性。因此，识别有前景的化合物体系、进行有针对性的设计以及基于经验的合成对于发现工作在感兴趣光谱区域的新型NLO材料至关重要。作为混合阴离子化合物的一个重要家族，包含以金属为中心的卤氧化物功能单元（[MO X ]（X = F、Cl、Br和I））的多功能金属卤氧化物正成为有趣的NLO材料的一个奇妙分支。特别是，当中心金属是d/d过渡金属或重后过渡金属时，有望得到许多具有优异功能的新型NLO材料。我们对金属卤氧化物用于NLO材料的最新成果进行的全面综述分为快速发展的具有单一类型卤素阴离子的NLO金属卤氧化物和新发现的具有混合卤素阴离子的NLO金属卤氧化物。在这里，我们主要关注具有相对较大NLO响应的金属卤氧化物的设计策略、结构化学、与NLO相关的性质以及结构 - 性质相关性。我们希望这篇综述能够为新兴金属卤氧化物用于NLO及其他应用的合理设计和未来发展提供见解。
