Three-Dimensional Fully Conjugated Carbaporphyrin Cage
Three-Dimensional Fully Conjugated Carbaporphyrin Cage
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DOI：
10.1021/jacs.8b11158
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发表时间：
2018-12-05
影响因子：
15
通讯作者：
Sessler, Jonathan L.
中科院分区：
文献类型：
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作者：
Ke, Xian-Sheng;Kim, Taeyeon;Sessler, Jonathan L.
通过一锅法制备完全共轭的三维 (3D) 扩展碳卟啉 (2)，该过程涉及含二苯并[g,p]屈的四吡咯前体 (1) 和五氟苯甲醛之间的 [2+4] 缩合反应，然后进行氧化。单晶X射线衍射分析表明2具有由四个二吡咯亚甲基和两个桥联二苯并[g,p]屈单元组成的笼状结构。根据 UV-vis-NIR 和 H-1 NMR 光谱推断，所制备的 2 是非芳香族的，并且具有接近零 (-1.75) 的核无关化学位移 (NICS) 值。相反，在用三氟乙酸（TFA）质子化后，笼子获得了整体芳香特征，这是从大的负NICS值（-11.63）和在感应电流密度（ACID）图的各向异性中观察到的变异性环电流以及约200°C中观察到的。激发态寿命延长 8 倍。此外，空腔的尺寸增加到约。根据单晶 X 射线衍射分析推导出质子化后的 143 埃(3)。据我们所知，这是迄今为止制备的最大的碳卟啉，也是第一个具有完全共轭的 3D 笼结构，其尺寸和电子特征可以通过质子化进行调整。
A fully conjugated three-dimensional (3D) expanded carbaporphyrin (2) was prepared in a one-pot procedure that involves a [2+4] condensation reaction between a dibenzo[g,p]chrysene-bearing tetrapyrrole precursor (1) and pentafluorobenzaldehyde, followed by oxidation. Single crystal X-ray diffraction analysis revealed that 2 possesses a cage-like structure consisting of four dipyrromethenes and two bridging dibenzo[g,p]chrysene units. As prepared, 2 is nonaromatic as inferred from UV-vis-NIR and H-1 NMR spectroscopy and a near-zero (-1.75) nucleus-independent chemical shift (NICS) value. In contrast, after protonation with trifluoroacetic acid (TFA), the cage gains global aromatic character as inferred from the large negative NICS value (-11.63) and diatropic ring current observed in the anisotropy of the induced current density (ACID) plot, as well as the ca. 8-fold increase in the excited state lifetime. In addition, the size of the cavity increases to ca. 143 angstrom(3) upon protonation as deduced from a single crystal X-ray diffraction analysis. To our knowledge, this is the largest carbaporphyrin prepared to date and the first with a fully conjugated 3D cage structure whose size and electronic features may be tuned through protonation.