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Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst.
Beilstein Journal of Organic Chemistry ( IF 2.7 ) Pub Date : 2020-08-31 , DOI: 10.3762/bjoc.16.179
Jannis Ludwig 1 , Julian Helberg 2 , Hendrik Zipse 2 , Rainer Herges 1
Affiliation  

We present the synthesis and the photochemical and catalytic switching properties of an azopyridine as a photoswitchable ligand, covalently attached to a Ni(II)-porphyrin. Upon irradiation with 530 nm (green light), the azopyridine switches to the cis configuration and coordinates with the Ni2+ ion. Light of 435 nm (violet) isomerizes the ligand back to the trans configuration, which decoordinates for steric reasons. This so-called record player design has been used previously to switch the spin state of Ni2+ between singlet and triplet. We now use the coordination/decoordination process to switch the catalytic activity of the dimethylaminopyridine (DMAP) unit. DMAP is a known catalyst in the nitroaldol (Henry) reaction. Upon coordination to the Ni2+ ion, the basicity of the pyridine lone pair is attenuated and hence the catalytic activity is reduced. Decoordination restores the catalytic activity. The rate constants in the two switching states differ by a factor of 2.2, and the catalytic switching is reversible.

中文翻译:

偶氮二甲基氨基吡啶官能化的Ni(II)-卟啉作为可光转换的亲核催化剂。

我们介绍了共价连接到Ni(II)-卟啉上的偶氮吡啶作为一种可光转换的配体的合成,光化学和催化转换特性。在530 nm(绿光)照射下,偶氮吡啶变为顺式构型并与Ni 2+离子配位。435 nm(紫色)的光将配体异构化为反式构型,由于空间原因,该构型发生了配位。这种所谓的电唱机设计先前已用于切换Ni 2+的自旋状态在单重态和三重态之间。现在,我们使用配位/去配位过程来切换二甲基氨基吡啶(DMAP)单元的催化活性。DMAP是硝基醛(Henry)反应中的已知催化剂。在与Ni 2+离子配位后,吡啶孤对的碱性减弱,因此催化活性降低。去配位可恢复催化活性。在两个切换状态下的速率常数相差2.2倍,并且催化切换是可逆的。
更新日期:2020-08-31
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