中山大学赵存元团队报道了一种新型杂化盐中由分子动力学逐步变化引起的特殊热致四态非线性光开关。相关研究成果于2021年10月15日发表在《德国应用化学》。

非线性光学通道中的开关材料是非线性光学材料科学中的一个重要研究方向。许多晶体NLO开关是基于结构相变产生的，但大多数都是在两种不同的二次谐波产生（SHG）状态之间的单步开关，很少涉及三种或更多的SHG状态。

该文中，研究人员报道了一种新的有机-无机杂化盐，(Me3NNH2)2[CdI4]，其是一种前所未有的在SHG静默态、中态、低态和高态之间进行可逆三步NLO切换的实例，在213–303 K的温度范围内其高对比度分别为~25.5/4.3/9.2。综合使用变温X射线单晶结构分析、介电常数、固态¹³C核磁共振光谱和Hirshfeld表面分析技术，研究人员揭示了这种四态可切换的SHG行为和极性有机阳离子的逐步变化的分子动力学密切相关。

该发现很好地证明了简单杂化盐分子动力学的复杂性及其在设计新型高级多步开关材料方面的潜力。

附：英文原文

Title: An Exceptional Thermally-Induced Four-State Nonlinear-Optical Switch Arising from Stepwise Molecular Dynamic Changes in a New Hybrid Salt

Author: Ying Zeng, Chun-Li Hu, Wei-Jian Xu, Teng-Wu Zeng, Zhao-Xiang Zhu, Xiao-Xian Chen, De-Xuan Liu, Yu-Jie Chen, Yue-Biao Zhang, Wei-Xiong Zhang, Xiao-Ming Chen

Issue&Volume: 2021-10-15

Abstract: The switch materials in channel of nonlinear optics (NLO) are of particular interest in NLO material science. Numerous crystalline NLO switches emerged based on structural phase transition, but most of them reveal single-step switch between two different second-harmonic-generation (SHG) states, very rare case involves three or more SHG states. Herein, we report a new organic-inorganic hybrid salt, (Me  3  NNH  2  )  2  [CdI  4  ], which is an unprecedented instance of reversible three-step NLO switches between SHG-silent, -medium, -low, and -high states, with high contrasts of ~25.5/4.3/9.2, respectively, in a temperature range of 213–303 K. By using the combined techniques of variable-temperature X-ray single-crystal structural analyses, dielectric constants, solid-state  13  C nuclear magnetic resonance spectroscopy, and Hirshfeld surface analyses, we disclosed that this four-state switchable SHG behavior is highly associated with the stepwise changed molecular dynamics of the polar organic cations. This finding well demonstrates a complexity of molecular dynamics in simple hybrid salts and its potential in designing new advanced multi-step switching materials.

DOI: 10.1002/anie.202110082

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202110082