Three-dimensional shape-persistent fluorescent nanocages: facile dynamic synthesis, photophysical properties, and surface morphologies.-猫眼课题宝

DOI：

10.1002/chem.200800154

发表时间：

2008-04

期刊：

Chemistry

影响因子：

通讯作者：

中科院分区：

文献类型：

作者：

Jia Luo;T. Lei;Xiaoguang Xu;Fangling Li;Yuguo Ma;Kai Wu;J. Pei

功能纳米结构具有独特的拓扑结构和特殊的性质，在自组装、主客体化学、催化和纳米技术等领域发挥着重要的作用。[1]在这些纳米尺寸的单元中，形状持久的人工架构提供固定的构象，这可能为可预测的组装、纳米纤维或客体包含物提供许多优势。[1，2]最近，许多通过多价组装具有封闭腔的刚性笼由于其在递送、提取、检测和各种微反应器中的应用而引起了相当大的兴趣。[1a然而，形状持久分子的合成通常是费力的，并且从共同母体在不同维度上的结构多样化也是困难的;另一方面，具有所需功能的分子的合理设计仍然是一个巨大的挑战。因此，开发一种有序的结构，以满足易于获得的多样化和合理设计具有可控溶解性和加工性的衍生物的需求，这也为灵活地模拟自然界中的多价组装提供了可能。[4]在我们之前的贡献中，我们报道了一个独特的3D骨架4a，如方案1所示，用于有机发光二极管中的纯蓝色发光体。[5]这种骨架的成功合成为我们通过正交和可重复修饰的位点实现三维衍生物的结构多样性提供了便利。因此，这种3D结构将提供具有不同功能的各种衍生物。本文中，我们利用该3D官能化“主体”（共价模板）与合适的平面“帽”偶联，以通过动态共价化学（DCC）实现具有强烈可见发光的C3对称纳米笼1a-c的定量形成。DCC由于其“错误检查”和“校对”的特性而成为一种高效和通用的合成策略，凭借其可逆性生成化学控制的产物。[6]此外，三个共轭臂的选择性引入不仅保证了荧光性质，而且提供了主体和客体之间的相互作用。方案2说明了纳米笼1a-c及其还原形式H12-1a-c的合成路线。首先，3D骨架4a用BBr 3脱甲基，然后在碱性条件下与正己基溴或2-（2-（2-甲氧基乙氧基）乙氧基）乙基4-甲基苯磺酸酯（TEG-OTs）反应，以高产率得到4 b或4c。随后，4和4-甲酰基苯基硼酸酯之间的有效Pd催化的Suzuki交叉偶联反应以良好的产率（75-86%）得到所需的醛2。与弱的非共价相互作用如氢键和金属配体配位作用相比，醛和胺之间的亚胺缩合反应似乎是构建更稳定的纳米笼的最有效的选择。[6e]首先，由醛2a和两当量的胺3 [7]形成纳米笼在无水CHCl 3或CH 2Cl 2溶液中进行。然而，形成了一定量的沉淀物，并且原位混合物的1H NMR光谱表明，即使在延长的加热时间之后也形成了不期望的混合物，这可能是由于亚胺中间体和起始材料在CHCl 3或CH 2Cl 2中的溶解度差。采用1，1，2，2-四氯乙烷（TCE）作为助溶剂促进缩合反应。令人高兴的是，将混合物[a] J. Luo，T. Lei，X.徐福，字- M.李教授Ma，K.北京师范大学化学学院生物有机化学与分子工程教育部重点实验室和高分子化学与物理教育部重点实验室

Functional nanostructures with intriguing topology and special properties have played important roles in self-assembly, host–guest chemistry, catalysis and nanotechnology.[1] Among these nanosized units, shape-persistent artificial architectures provide fixed conformations, which might offer many advantages for predictable assembly, nanofabrication, or guest inclusion.[1, 2] Recently, many rigid cages with confined cavities through multivalent assembly have attracted considerable interest due to their applications in delivery, extraction, detection and various microreactors.[1a, c, 3] However, the synthesis of shape-persistent molecules is usually laborious, and the structural diversification in different dimensions from a common parent is also difficult; on the other hand, rational design of molecules with desired functionalities still remains a great challenge. Therefore, it is imperative to develop a well-organized structure to meet the requirement of readily available diversification and rational design of derivatives with controllable solubility and processibility, which also provides the possibility to agilely mimic multivalent assembly in nature.[4] In our previous contribution, we reported a unique 3D skeleton 4a as shown in Scheme 1 for pure blue emitters applied in organic light-emitting diodes.[5] The success of synthesizing such skeleton provides us with convenience to realize the structural diversity of 3D derivatives through orthogonally and distinguishably modifiable sites. As a result, such a 3D structure would offer various derivatives with diverse functionalities. Herein, we utilize this 3D functionalized “body”(a covalent template) to couple with suitable planar “caps” to achieve quantitative formation of C3 symmetrical nanocages 1a–c with intensive visible luminescence through dynamic covalent chemistry (DCC). DCC emerges as an efficient and versatile synthetic strategy due to its “errorchecking” and “proof-reading” features, generating thermodynamically controlled products by virtue of its reversibility.[6] Additionally, the selective introduction of three conjugated arms not only guarantees the fluorescent property, but also offers the interactions between host and guest. Scheme 2 illustrates the synthetic route to nanocages 1a–c and their reduced forms H12-1a–c. First, demethylation of 3D skeleton 4a by BBr3 followed by reacting with n-hexylbromide or 2-(2-(2-methoxyethoxy) ethoxy) ethyl 4-methylbenzenesulfonate (TEG-OTs) under basic condition afforded 4b or 4c in high yield. Subsequently, efficient Pd-catalyzed Suzuki cross-coupling reaction between 4 and 4-formylphenylboronic ester gave desired aldehyde 2 in good yields (75–86%). Compared with weak noncovalent interactions such as hydrogen-bonding and metal–ligand coordination, imine condensation between aldehydes and amines seems to be the most valid choice to construct more stable nanocages.[6e] First, the formation of the nanocages from aldehyde 2a and two equivalents of amine 3 [7] was carried out in refluxing CHCl3 or CH2Cl2 solution. However, amounts of precipitates were formed and 1H NMR spectra of the in situ mixture suggested that an undesirable mixture was formed even after extended heating time, which might be owing to the poor solubility of the imine intermediates and starting materials in CHCl3 or CH2Cl2. 1, 1, 2, 2-Tetrachloroethane (TCE) was employed as a co-solvent to promote the condensation reaction. To our delight, refluxing the mixture [a] J. Luo, T. Lei, X. Xu, F.-M. Li, Prof. Y. Ma, Prof. K. Wu, Prof. J. Pei Key Laboratories of Bioorganic Chemistry and Molecular Engineering and of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry …

Three-dimensional shape-persistent fluorescent nanocages: facile dynamic synthesis, photophysical properties, and surface morphologies.

文献摘要

被引文献

相似文献