Institut de Química Computacional i Catàlisi, Facultat de Ciències, Universitat de Girona, ES-17003 Girona, Spain.
Department of Chemistry and Biomedical Sciences, Faculty of Health and Life Sciences, Linnaeus University, SE-45041 Kalmar, Sweden.
J Org Chem. 2021 Apr 16;86(8):5552-5559. doi: 10.1021/acs.joc.1c00063. Epub 2021 Mar 30.
Synthetic molecular motors driven by / photoisomerization reactions are able to produce unidirectional rotary motion because of a structural asymmetry that makes one direction of rotation more probable than the other. In most such motors, this asymmetry is realized through the incorporation of a chemically asymmetric carbon atom. Here, we present molecular dynamics simulations based on multiconfigurational quantum chemistry to investigate whether the merits of this approach can be equaled by an alternative approach that instead exploits isotopic chirality. By first considering an -methylpyrrolidine-cyclopentadiene motor design, it is shown that isotopically chiral variants of this design undergo faster photoisomerizations than a chemically chiral counterpart, while maintaining rotary photoisomerization quantum yields of similarly high magnitude. However, by subsequently considering a pyrrolinium-cyclopentene design, it is also found that the introduction of isotopic chirality does not provide any control of the directionality of the photoinduced rotations within this framework. Taken together, the results highlight both the potential usefulness of isotopic rather than chemical chirality for the design of light-driven molecular motors, and the need for further studies to establish the exact structural circumstances under which this asymmetry is best exploited.
受/光致异构反应驱动的合成分子马达能够产生单向旋转运动，这是由于结构不对称使得一种旋转方向比另一种更有可能。在大多数此类马达中，这种不对称性是通过引入化学不对称碳原子来实现的。在这里，我们进行了基于多组态量子化学的分子动力学模拟，以研究是否可以通过替代方法来实现这种方法的优点，而这种替代方法则利用同位素手性。首先考虑 -甲基吡咯烷-环戊二烯马达设计，结果表明，与化学手性对应物相比，该设计的同位素手性变体经历更快的光致异构化，同时保持类似高幅度的旋转光致异构化量子产率。然而，随后考虑吡咯烷-环戊烯设计，也发现引入同位素手性在该框架内并没有提供对光诱导旋转方向的任何控制。总之，这些结果既强调了在设计光驱动分子马达时使用同位素而不是化学手性的潜在有用性，也需要进一步的研究来确定在何种确切结构条件下最好地利用这种不对称性。
