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首页> 外文期刊>Chemistry: A European journal >New Mechanistic Insight in the Thermal Helix Inversion of Second-Generation Molecular Motors
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New Mechanistic Insight in the Thermal Helix Inversion of Second-Generation Molecular Motors

机译：第二代分子电动机热螺旋逆转的新机理研究

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摘要

The introduction of dibenzo-cyclohepten-5-ylidene as part of a unidirectional light-driven molecular motor allows a more complete picture of the pathway of thermal helix inversion to be developed. The most stable conformation is similar to that found in related motors in that it has, overall, an anti-folded structure with the substituent at the stereogenic centre adopting an axial orientation. Photochemical cis/trans isomerisation at -40 degrees C results in the formation of an isomer in a syn-folded conformation with the methyl group in an axial orientation. This contrasts with previous studies on related molecular rotary motors. The conformation of the higher energy intermediate typically observed for this class of compound is the anti-folded conformation, in which the methyl group is in an equatorial orientation. This conformation is available through an energetically uphill upper half ring inversion of the observed photochemical product. However, this pathway competes with a second process that leads to the more stable anti-folded conformation in which the methyl group is oriented axially. It has been shown that the conformations and pathways available for second-generation molecular motors can be described by using similar overall geometries. Differences in the metastable high-energy species are attributable to the relative energy and position on the reaction coordinate of the transition states. Kinetic studies on these new molecular motors thus provide important insights into the conformational dynamics of the rotation cycle.
机译：作为单向光驱动分子马达的一部分，引入二苯并环庚基-5-亚烷基使得可以更完整地了解热螺旋转化的途径。最稳定的构象与相关马达中的构象相似，因为它总体上具有抗折叠结构，在立体中心的取代基采用轴向取向。在-40℃下光化学的顺式/反式异构化导致形成与甲基在轴向方向上同折叠构型的异构体。这与有关分子旋转电动机的先前研究形成对比。通常对于这类化合物观察到的较高能中间体的构象是抗折叠构象，其中甲基处于赤道取向。通过观察到的光化学产物的能量上坡上半环反演可获得该构象。然而，该途径与第二过程竞争，该第二过程导致其中甲基轴向取向的更稳定的抗折叠构象。已经表明，可以通过使用相似的整体几何形状来描述可用于第二代分子马达的构象和途径。亚稳态高能物种的差异可归因于过渡态反应坐标上的相对能量和位置。因此，对这些新型分子马达的动力学研究为旋转循环的构象动力学提供了重要的见识。

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