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首页> 外文期刊>Chemistry: A European journal >A Light-Controlled Molecular Brake with Complete ON-OFF Rotation
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A Light-Controlled Molecular Brake with Complete ON-OFF Rotation

机译：具有完全开-关旋转的光控分子制动器

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摘要

A light-controlled molecular machine based on cyclic azobenzenophanes consisting of a dioxynaphthalene rotating unit and a photoisomerizable dioxyazobenzene unit bridged by methylene spacers is reported. In compounds 1 and 2, 1,5- and 2,6-dioxynaphthalene moieties, respectively, are linked to p-dioxyazobenzene by different methylene spacers (n=2 in la and 2; n=3 in 1b), whereas a 1,5-dioxynaphthalene moiety is bonded to m-dioxyazobenzene by bismethylene spacers in 3. In 1b and 2, the naphthalene ring can rotate freely in both the trans and cis states at room temperature. The rotation speed can be controlled either by photoinduced reversible trans cis (E-Z) isomerization of the azobenzene or by keeping the system at low temperature, as is evident from its NMR spectra. Furthermore, for the first time, we demonstrate a light-controlled molecular brake, wherein the rotation of the naphthalene moiety through the cyclophane is completely OFF in the trans isomer of compound 3 due to its smaller cavity size. Such restricted rotation imparts planar chirality to the molecule, and the corresponding enantiomers could be resolved by chiral HPLC. However, the rotation of the naphthalene moiety is rendered ON in the cis isomer due to its increased cavity size, and it is manifested experimentally by the racemization of the separated enantiomers by photoinduced E-Z isomerization.
机译：报道了一种基于环偶氮苯并oph烷的光控分子机器，该环偶氮苯并oph烷由二氧萘旋转单元和由亚甲基间隔基桥接的可光异构的二氧偶氮苯单元组成。在化合物1和2中，分别通过不同的亚甲基间隔基（n = 2在la和2中; n = 3在1b中）将1,5-和2,6-二氧萘基与对-二氧偶氮苯相连，而1，在图3中，通过双亚甲基间隔基将5-二氧萘部分与间二氧偶氮苯结合。在1b和2中，萘环在室温下可以以反式和顺式自由旋转。旋转速度可以通过偶氮苯的光诱导可逆顺式（E-Z）异构化或通过将系统保持在低温下来控制，这从其NMR光谱中可以明显看出。此外，我们首次展示了一种光控分子制动器，其中，由于化合物3的反式异构体的空腔尺寸较小，萘部分通过环烷的旋转在化合物3的反式异构体中完全关闭。这种受限的旋转赋予分子平面手性，并且相应的对映异构体可以通过手性HPLC拆分。然而，由于萘部分腔尺寸的增加，萘部分的旋转在顺式异构体中处于ON状态，并且这通过光诱导的E-Z异构化使分离的对映异构体外消旋而在实验上得到证明。

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