Dimesitylborylethynylated Arenes: Unique Electronic and Photophysical Properties Caused by Ethynediyl (C≡C) Spacers
Dimesitylborylethynylated Arenes: Unique Electronic and Photophysical Properties Caused by Ethynediyl (C≡C) Spacers
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二甲基硼基乙炔化芳烃：乙炔二基 (C=C) 间隔基带来的独特电子和光物理性质
DOI：
10.1002/chem.202004744
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Akita Munetaka
中科院分区：
文献类型：
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作者：
Mishiba Kentaro;Tanaka Yuya;Akita Munetaka
在此，我们报道了具有一个或两个二均三甲苯硼乙炔基外围的芳烃的合成及其电化学和物理性质。通过亲核取代反应容易制备的单硼基化合物（1）和二硼基化合物（2）在固态下对空气和水分相当稳定。插入的乙炔二基（C C）间隔消除了庞大的二均三甲苯基硼基和芳环之间的空间位阻，导致B−C C−Ar键上的有效π共轭，如循环伏安法所示。尽管结构上有很小的差异，但苯、萘和蒽衍生物的物理化学性质是不同的。从苯衍生物中几乎没有观察到发射，而蒽衍生物在溶液和固态中都以高量子产率发射。值得注意的是，萘衍生物显示出聚集诱导的发射行为。与目前报道的常见的空间拥挤的三芳基硼烷衍生物不同，蒽衍生物显示出π-π*-型吸收和发射带，其来自硼中心和蒽部分之间的有效分子内轨道相互作用，如DFT计算所支持的。结果，二均三甲苯基硼基乙炔基取代基有效地降低了芳烃部分的LUMO能级，而HOMO能级几乎不受影响，从而得到具有可控HOMO-LUMO间隙的材料。
Herein, we report the synthesis and electrochemical and photophysical properties of aromatic hydrocarbons having one or two dimesitylborylethynyl peripherals. The mono‐ (1) and diboryl compounds (2), readily prepared by nucleophilic substitution reaction, are fairly stable to air and moisture in the solid state. The inserted ethynediyl (C≡C) spacer cancels the steric hindrance between the bulky dimesitylboryl groups and aromatic rings, leading to effective π conjugation over the B−C≡C−Ar linkages, as revealed by cyclic voltammetry. Despite the small structural differences, the photophysical properties of the benzene, naphthalene, and anthracene derivatives are different. Virtually no emission was observed from the benzene derivatives, whereas the anthracene derivatives emitted with high quantum yields both in solution and in the solid state. Notably, the naphthalene derivatives showed aggregation‐induced emission behavior. Unlike the common sterically congested triarylborane derivatives reported so far, the anthracene derivatives showed π–π*‐type absorption and emission bands, which derive from efficient intramolecular orbital interactions between the boron centers and anthracene moieties, as supported by DFT calculations. As a result, the dimesitylborylethynyl substituents effectively lower the LUMO levels of the aromatic hydrocarbon parts, whereas the HOMO levels are almost unaffected, thereby leading to materials with controllable HOMO–LUMO gaps.