Synthesis, Thermal, and Optical Properties of Tris(5‐aryl‐1,3,4‐oxadiazol‐2‐yl)‐1,3,5‐triazines, New Star‐Shaped Fluorescent Discotic Liquid Crystals
Synthesis, Thermal, and Optical Properties of Tris(5‐aryl‐1,3,4‐oxadiazol‐2‐yl)‐1,3,5‐triazines, New Star‐Shaped Fluorescent Discotic Liquid Crystals
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DOI：
10.1002/chem.201902975
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发表时间：
2019-11
期刊：
影响因子：
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通讯作者：
Natalie Tober;Thorsten Rieth;M. Lehmann;H. Detert
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文献类型：
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作者：
Natalie Tober;Thorsten Rieth;M. Lehmann;H. Detert
摘要本文报道了三芳基二唑基三嗪类化合物（TOTs）、具有1,3,5 -三嗪中心、5 -苯基- 1,3,4 -恶二唑臂的c3 -对称星形中间体和各种周边烷氧基侧链的合成。在中心三嗪三羧酸和合适的芳基四唑上进行三次Huisgen反应，得到标题化合物。本研究包括选定的具有苯中心的类似物，并允许评估中心单元对物理性质的影响。研究了这些化合物的热（差示扫描量热法，DSC，偏振光学显微镜，POM），光学（紫外/可见，荧光），电学（飞行时间，TOF）和结构（单晶，广角X射线散射，WAXS）性质。烷氧基链长度和取代模式的修改允许调整物理性质。根据共轭长度、供体-受体取代和溶剂极性的不同，tot会发出蓝色到黄色的光，而浓度猝灭和聚集会增强发射。中间相的宽度通常在ΔT= 100-150 K左右，但甚至可以超过220 K。偏振光学显微镜和定向细丝的X射线衍射结果表明，tot是一种具有长程六方柱状结构的高度有序液晶。
Abstract The synthesis of tris(aryloxadiazolyl)triazines (TOTs), C 3‐symmetrical star‐shaped mesogenes with a 1,3,5‐triazine center, 5‐phenyl‐1,3,4‐oxadiazole arms, and various peripheral alkoxy side chains is reported. Threefold Huisgen reaction on a central triazine tricarboxylic acid and suitable aryltetrazoles yields the title compounds. Selected analogues with a benzene center are included in this study and allow for an evaluation of the impact of the central unit on the physical properties. Thermal (differential scanning calorimetry, DSC; polarization optical microscopy, POM), optical (UV/Vis, fluorescence), electric (time of flight, TOF), and structural (single crystal; wide‐angle X‐ray scattering, WAXS) properties of these compounds were investigated. The modification of alkoxy chain length and substitution pattern allows for a tuning of the physical properties. TOTs emit blue to yellow light, depending on conjugation length, donor–acceptor substitution, and solvent polarity, whereas concentration quenches and aggregation enhances the emission. The width of the mesophases is typically around ΔT=100–150 K but can even exceed 220 K. Polarization optical microscopy and X‐ray diffraction on oriented filaments reveal that TOTs are highly ordered liquid crystals (LCs) with long‐range hexagonal columnar structure.