Highly Efficient Blue Fluorescence from 3,2'- Silylene-Bridged 2-Phenylindoles in the Solid State
Highly Efficient Blue Fluorescence from 3,2'- Silylene-Bridged 2-Phenylindoles in the Solid State
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固态 3,2- 亚硅基桥接 2-苯基吲哚发出高效蓝色荧光
DOI：
10.1021/jp201168x
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
T.
中科院分区：
文献类型：
--
作者：
Shimizu;M.; Mochida;K.; Hiyama;T.
以2-（2-吲哚基硅基）芳基三氟甲磺酸酯为原料，在钯催化下进行硅迁移分子内偶联反应，高产率地合成了3，2 ′-硅亚烷基桥联的2-苯基吲哚。通过热重分析（TGA）表明苯并噻咯稠合吲哚的高热稳定性。吸收光谱表明，吸收边，即HOMO-LUMO能隙，可以有效地调整取代与功能基团，如氯，氰基，甲氧基，和苯基的间位相对于氮和硅，而没有有效的共轭之间的核心和氮上的芳基。通过密度泛函理论计算，很好地再现了由官能团变化引起的HOMO-LUMO能隙的变化。吲哚类化合物在环己烷、粉末以及掺杂的聚甲基丙烯酸甲酯（PMMA）薄膜中均表现出高至优异的量子产率的蓝色荧光。各吲哚的最大发射峰均发生红移，其红移顺序为：环己烷→PMMA膜→粉末。对二异丙基亚甲硅烷基桥连的母体吲哚的X射线分析表明，晶体中没有像π-π堆积那样的紧密接触，这可能是由于庞大的亚甲硅烷基桥的空间效应。对3，2-二异丙基亚甲基桥连的2-苯基吲哚的物理化学性质的研究表明，固态碳类似物的量子产率远低于相应的甲硅烷基桥连的吲哚。因此，发现亚甲硅烷基桥对于使用基于2-苯基吲哚框架的分子设计获得高至优异的固态量子效率是必要的。
3,2′-Silylene-bridged 2-phenylindoles were prepared in high yields by palladium-catalyzed silicon-migrative intramolecular coupling of 2-(2-indolylsilyl)aryl triflates. The high thermal stability of the benzosilole-fused indoles was indicated by thermogravimetric analysis (TGA). The absorption spectra revealed that the absorption edges, namely, the HOMO–LUMO energy gaps, could be effectively tuned by substitution with functional groups such as chloro, cyano, methoxy, and phenyl at the meta-positions with respect to nitrogen and silicon, whereas there was no effective conjugation between the core and an aryl group on nitrogen. The changes in the HOMO–LUMO gaps, which were induced by variation of the functional groups, were well reproduced by density functional theory calculation. The indoles exhibited blue fluorescence with high-to-excellent quantum yields both in cyclohexane and in powder as well as in doped poly(methyl methacrylate) (PMMA) films. The emission maxima of each indole exhibited a red-shift, which followed the general order: cyclohexane→PMMA film→powder. X-ray analysis of the diisopropylsilylene-bridged parent indole indicated that there was no close contact like π–π stacking in the crystal, presumably because of the steric effect of the bulky silylene bridge. Examination of the photophysical properties of 3,2-diisopropylmethylene-bridged 2-phenylindole revealed that the quantum yields of the carbon analogue in the solid state were much lower than the corresponding silylene-bridged indole. Thus, the silylene bridge is found to be essential for obtaining high-to-excellent solid-state quantum efficiency using a molecular design based on a 2-phenylindole framework.