An antiaromatic-walled nanospace
An antiaromatic-walled nanospace
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DOI：
10.1038/s41586-019-1661-x
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发表时间：
2019-10
期刊：
影响因子：
64.8
通讯作者：
Masahiro Yamashina;Yuya Tanaka;Roy Lavendomme;Tanya K. Ronson;M. Pittelkow;J. Nitschke
中科院分区：
文献类型：
--
作者：
Masahiro Yamashina;Yuya Tanaka;Roy Lavendomme;Tanya K. Ronson;M. Pittelkow;J. Nitschke
在过去的几十年里，已经报道了几种分子笼、宿主和包裹纳米尺寸空腔的纳米孔材料，包括配位驱动的纳米笼。这种纳米笼被广泛应用于分子识别、分离、稳定和促进不寻常的化学反应，以及其他应用，，，，，，-。大多数已报道的分子宿主内的纳米空间被芳香壁所限制，其性质有助于确定主客行为。然而，由于抗芳香族化合物的不稳定性，纳米空间被抗芳香族壁包围的笼尚未被开发出来；因此，反芳香壁对纳米空间性质的影响仍然未知。在这里，我们展示了在一个由四个金属离子组成的自组装笼中构建一个具有六个相同的抗芳香壁的抗芳香壁纳米空间。计算表明，围绕该纳米空间的反芳香基团的磁效应相互增强。结合客体分子的1h核磁共振（NMR）信号证实了这一预测，由于周围环的联合反芳脱屏蔽作用，观察到客体分子的化学位移值高达百万分之24 （ppm）。这个值比自由客体的值偏移了15ppm，是迄今为止观察到的由反芳香环境引起的最大1h NMR化学位移。因此，这个笼子可以被认为是一种核磁共振移位试剂，它将客体信号移动到通常的核磁共振频率范围之外，并为进一步探索反芳香环境对纳米空间的影响开辟了道路。
Over the past few decades, several molecular cages, hosts and nanoporous materials enclosing nanometre-sized cavities have been reported, , , –, including coordination-driven nanocages. Such nanocages have found widespread use in molecular recognition, separation, stabilization and the promotion of unusual chemical reactions, among other applications, , , , , , –. Most of the reported nanospaces within molecular hosts are confined by aromatic walls, the properties of which help to determine the host–guest behaviour. However, cages with nanospaces surrounded by antiaromatic walls have not yet been developed, owing to the instability of antiaromatic compounds; as such, the effect of antiaromatic walls on the properties of nanospaces remains unknown. Here we demonstrate the construction of an antiaromatic-walled nanospace within a self-assembled cage composed of four metal ions with six identical antiaromatic walls. Calculations indicate that the magnetic effects of the antiaromatic moieties surrounding this nanospace reinforce each other. This prediction is confirmed by1H nuclear magnetic resonance (NMR) signals of bound guest molecules, which are observed at chemical shift values of up to 24 parts per million (ppm), owing to the combined antiaromatic deshielding effect of the surrounding rings. This value, shifted 15 ppm from that of the free guest, is the largest1H NMR chemical shift displacement resulting from an antiaromatic environment observed so far. This cage may thus be considered as a type of NMR shift reagent, moving guest signals well beyond the usual NMR frequency range and opening the way to further probing the effects of an antiaromatic environment on a nanospace.