Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo, Japan.
J Am Chem Soc. 2012 Mar 28;134(12):5652-61. doi: 10.1021/ja3001979. Epub 2012 Mar 14.
Color-tunable luminescent ionic liquid crystals have been designed as a new series of luminescent materials. To achieve tuning of emission colors, intramolecular charge transfer (ICT) character has been incorporated into tripodal molecules. A series of the compounds has three chromophores in each molecule, incorporated with both electron-donating moieties such as alkylaminobenzene and alkoxybenzene, and electron-accepting moieties such as pyridinium, pyrimidinium, and quinolinium parts. These C(3)-symmetrical molecules self-assemble into liquid-crystalline (LC) columnar (Col) structures over wide temperature ranges through nanosegregation between ionic moieties and nonionic aliphatic chains. Photoluminescent (PL) emissions of these tripodal molecules are observed in the visible region both in the self-assembled condensed states and in solutions. For example, a pyrimidinium salt with didodecylaminobenzene moieties exhibits yellowish orange emission (λ(em) = 586 nm in a thin film). Multicolor PL emissions are successfully achieved by simple tuning of changing electron-donating and electron-accepting moieties of the compounds, covering the visible region from blue-green to red. It has been revealed that ICT processes in the excited states and weak intermolecular interactions play important roles in the determination of the PL properties of the materials, by measurements of UV-vis absorption and emission spectra, fluorescence lifetimes, and PL quantum yields.
可调节颜色的发光离子液体晶体已被设计为一系列新型发光材料。为了实现发射颜色的调节，已将分子内电荷转移（ICT）特性纳入三脚架分子中。一系列化合物在每个分子中都有三个发色团，同时包含供电子部分（如烷基氨基苯和烷氧基苯）和受电子部分（如吡啶鎓、嘧啶鎓和喹啉鎓部分）。这些 C(3)-对称分子通过离子部分和非离子脂肪链之间的纳米分离，在很宽的温度范围内自组装成液晶（LC）柱状（Col）结构。这些三脚架分子的光致发光（PL）发射在自组装的凝聚态和溶液中都在可见区域中观察到。例如，带有二癸基氨基苯部分的嘧啶盐表现出黄橙色发射（在薄膜中为 586nm 的λ(em)）。通过简单调节化合物的供电子和受电子部分的变化，可以成功实现多色 PL 发射，覆盖从蓝绿色到红色的可见区域。通过测量紫外可见吸收和发射光谱、荧光寿命和 PL 量子产率，已经揭示了激发态中的 ICT 过程和弱分子间相互作用在确定材料的 PL 性质方面起着重要作用。
