Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.
Institute for Molecular Design and Synthesis, Tianjin University, Tianjin 300072, China.
J Am Chem Soc. 2020 May 13;142(19):8938-8945. doi: 10.1021/jacs.0c02311. Epub 2020 Apr 23.
We report the encapsulation of free-base and zinc porphyrins by a tricyclic cyclophane receptor with subnanomolar binding affinities in water. The high affinities are sustained by the hydrophobic effect and multiple [CH···π] interactions covering large [π···π] stacking surfaces between the substrate porphyrins and the receptor. We discovered two co-conformational isomers of the 1:1 complex, where the porphyrin is orientated differently inside the binding cavity of the receptor on account of its tricyclic nature. The photophysical properties and chemical reactivities of the encapsulated porphyrins are modulated to a considerable extent by the receptor. Improved fluorescence quantum yields, red-shifted absorptions and emissions, and nearly quantitative energy transfer processes highlight the emergent photophysical enhancements. The encapsulated porphyrins enjoy unprecedented chemical stabilities, where their D/H exchange, protonation, and solvolysis under extremely acidic conditions are completely blocked. We anticipate that the ultrahigh stabilities and improved optical properties of these encapsulated porphyrins will find applications in single-molecule materials, artificial photodevices, and biomedical appliances.
我们报告了一种三环环芳受体对游离碱基和锌卟啉的包封，在水中具有纳摩尔级的结合亲和力。这种高亲和力是由疏水效应和多个[CH···π]相互作用维持的，这些相互作用覆盖了基质卟啉和受体之间的大[π···π]堆积表面。我们发现了 1:1 配合物的两种共构异形体，其中由于其三环性质，卟啉在受体的结合腔内以不同的方式取向。被包封卟啉的光物理性质和化学反应性在相当大的程度上受到受体的调制。荧光量子产率的提高、吸收和发射的红移，以及近乎定量的能量转移过程突出了新兴的光物理增强。被包封的卟啉具有前所未有的化学稳定性，其 D/H 交换、质子化和在极酸性条件下的溶剂解完全被阻断。我们预计，这些被包封卟啉的超高稳定性和改进的光学性质将在单分子材料、人工光电设备和生物医学设备中得到应用。
