School of Chemistry, Cardiff University , Park Place Main Building, Cardiff CF10 3AT, United Kingdom.
Department of Chemistry, University of Namur (UNamur) , Rue de Bruxelles 61, Namur 5000, Belgium.
J Am Chem Soc. 2017 Apr 19;139(15):5503-5519. doi: 10.1021/jacs.7b01477. Epub 2017 Apr 4.
The divergent synthesis of two series of borazino-doped polyphenylenes, in which one or more aryl units are replaced by borazine rings, is reported for the first time, taking advantage of the decarbonylative [4 + 2] Diels-Alder cycloaddition reaction between ethynyl and tetraphenylcyclopentadienone derivatives. Because of the possibility of functionalizing the borazine core with different groups on the aryl substituents at the N and B atoms of the borazino core, we have prepared borazino-doped polyphenylenes featuring different doping dosages and orientations. To achieve this, two molecular modules were prepared: a core and a branching unit. Depending on the chemical natures of the central aromatic module and the reactive group, each covalent combination of the modules yields one exclusive doping pattern. By means of this approach, three- and hexa-branched hybrid polyphenylenes featuring controlled orientations and dosages of the doping BN rings have been prepared. Detailed photophysical investigations showed that as the doping dosage is increased, the strong luminescent signal is progressively reduced. This suggests that the presence of the BN rings engages additional deactivation pathways, possibly involving excited states with an increasing charge-separated character that are restricted in the full-carbon analogues. Notably, a strong effect of the orientational doping on the fluorescence quantum yield was observed for those hybrid polyphenylene structures featuring low doping dosages. Finally, we showed that Cu-catalyzed 1,3-dipolar cycloaddition is also chemically compatible with the BN core, further endorsing the inorganic benzene as a versatile aromatic scaffold for engineering of molecular materials with tailored and exploitable optoelectronic properties.
首次报道了利用炔基和四苯环戊二烯酮衍生物之间的去羰基[4+2]Diels-Alder 环加成反应，对两个系列的硼嗪掺杂聚苯进行了发散合成，其中一个或多个芳基单元被硼嗪环取代。由于可以在硼嗪核的 N 和 B 原子上的芳基取代基上用不同的基团官能化硼嗪核，因此我们已经制备了具有不同掺杂剂量和取向的硼嗪掺杂聚苯。为了实现这一目标，我们制备了两个分子模块：一个核心和一个分支单元。根据中心芳族模块和反应性基团的化学性质，每个模块的共价组合都会产生一种独特的掺杂模式。通过这种方法，已经制备了具有可控取向和掺杂 BN 环剂量的三分支和六分支杂化聚苯。详细的光物理研究表明，随着掺杂剂量的增加，强发光信号逐渐降低。这表明 BN 环的存在引入了额外的失活途径，可能涉及具有增加的电荷分离特征的激发态，这些激发态在全碳类似物中受到限制。值得注意的是，对于那些具有低掺杂剂量的杂化聚苯结构，取向掺杂对荧光量子产率有很强的影响。最后，我们表明 BN 核与 Cu 催化的 1,3-偶极环加成也是化学相容的，进一步证明了无机苯是一种多功能的芳基支架，可用于设计具有可定制和可利用光电性能的分子材料。
