Computational Insight to Improve the Thermal Isomerisation Performance of Overcrowded Alkene-Based Molecular Motors through Structural Redesign.
Computational Insight to Improve the Thermal Isomerisation Performance of Overcrowded Alkene-Based Molecular Motors through Structural Redesign.
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DOI：
10.1002/cphc.201600766
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发表时间：
2016-11
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通讯作者：
Baswanth Oruganti;Jun Wang;B. Durbeej
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作者：
Baswanth Oruganti;Jun Wang;B. Durbeej
合成的过度拥挤的基于烯烃的分子马达通过顺序的光化学和热异构化步骤实现一个马达半部（转子）相对于另一个马达半部（定子）的360°单向旋转运动。为了促进和扩大这些电动机在各种应用中的使用，重要的是研究增加控制旋转运动的反作用的速率和效率的方法。在这里，我们使用计算方法来探索是否可以通过减少电机的尺寸来进一步改善这种类型的一些最快的可用电机的热异构化性能。提出了三个新的重新设计的电机，结合联合收割机茚满转子与环己二烯，吡喃或噻喃定子，我们首先使用多构型量子化学方法来验证，这些电机的光异构化维持单向旋转运动。然后，通过进行密度泛函计算，我们确定两个逐步和协调机制的热异构化的电机，并表明，这些过程的速率决定自由能势垒高达25千焦摩尔-1小于原来的电机。此外，重新设计的发动机的热异构化在更少的步骤中进行。总而言之，结果表明，重新设计的电机是有用的模板，用于改善现有的过度拥挤的基于烯烃的电机的热异构化性能。
Synthetic overcrowded alkene-based molecular motors achieve 360° unidirectional rotary motion of one motor half (rotator) relative to the other (stator) through sequential photochemical and thermal isomerisation steps. In order to facilitate and expand the use of these motors for various applications, it is important to investigate ways to increase the rates and efficiencies of the reactions governing the rotary motion. Here, we use computational methods to explore whether the thermal isomerisation performance of some of the fastest available motors of this type can be further improved by reducing the sizes of the motor halves. Presenting three new redesigned motors that combine an indanylidene rotator with a cyclohexadiene, pyran or thiopyran stator, we first use multiconfigurational quantum chemical methods to verify that the photoisomerisations of these motors sustain unidirectional rotary motion. Then, by performing density functional calculations, we identify both stepwise and concerted mechanisms for the thermal isomerisations of the motors and show that the rate-determining free-energy barriers of these processes are up to 25 kJ mol-1 smaller than those of the original motors. Furthermore, the thermal isomerisations of the redesigned motors proceed in fewer steps. Altogether, the results suggest that the redesigned motors are useful templates for improving the thermal isomerisation performance of existing overcrowded alkene-based motors.