Photoinduced conformational switch of enantiopure azobenzenes controlled by a sulfoxide
Photoinduced conformational switch of enantiopure azobenzenes controlled by a sulfoxide
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DOI：
10.1021/ja070163o
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发表时间：
2007-06-06
影响因子：
15
通讯作者：
Spada, Gian Piero
中科院分区：
文献类型：
--
作者：
Carreno, M. Carmen;Garcia, Isabel;Spada, Gian Piero
区域选择性地合成了两个系列的对映体纯的偶氮苯，其偶氮基团的邻位或Meta位分别带有对甲苯亚砜。两者都可以作为对映体纯分子开关，由于立体硫的存在而显示出不同的结构特征。通过紫外-可见光谱、圆二色性（CD）、NMR和手性HPLC研究的光异构化过程证明了亚砜的双重作用。转移的手性从亚砜的偶氮系统中观察到的CD在顺式和反式异构体的Meta亚磺酰基衍生物3，而这种扰动是显而易见的邻亚磺酰基系列7仅在顺式异构体。NMR研究表明，双芳族亚砜的s-顺式刚性构象固定在每个系列的反式和顺式异构体中的整个系统的不同取向，通过迫使最终的U形结构在顺式-3和S形结构在顺式-7。在反式和顺式异构体中测量到非常不同的比旋光度值，也反映了在光稳态中存在不同的手性实体。不同构象状态之间发生的简单和可逆的变化可以在几种分子开关的光控中找到应用。
Two series of enantiopure azobenzenes with a p-tolylsulfoxide at the ortho or meta position with respect to the azo group, have been regioselectively synthesized. Both can act as enantiopure molecular switches showing different structural features owing to the presence of the stereogenic sulfur. The photoisomerization process, studied by UV-vis, circular dichroism (CD), NMR, and chiral HPLC evidenced a double role of the sulfoxide. A transfer of chirality from the sulfoxide to the azo system was observed by CD in both cis and trans-isomers of the meta sulfinyl derivatives 3, whereas this perturbation was evident for the ortho sulfinyl series 7 only in the cis isomer. The NMR study evidenced that the s-cis rigid conformation of the bisaromatic sulfoxide was fixing a different orientation of the overall system in each series both in the trans and cis isomers, by forcing a final U-shaped structure in cis-3 and an S-shaped structure in cis-7. Very different values of specific optical rotations were measured in both trans and cis isomers, also reflecting the existence of distinct chiral entities in the photostationary states. The easy and reversible changes occurring between different conformational states could find applications in the photocontrol of several molecular switches.