Liu Lihong, Fang Wei-Hai, Martinez Todd J
Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
Department of Chemistry and PULSE Institute, Stanford University, Stanford, California 94305, United States.
J Am Chem Soc. 2023 Mar 29;145(12):6888-6898. doi: 10.1021/jacs.3c00275. Epub 2023 Mar 15.
Light-driven molecular motors have generated considerable interest due to their potential applications in material and biological systems. Recently, Greb and Lehn reported a new class of molecular motors, chiral -alkyl imines, which undergo unidirectional rotation induced by light and heat. The mechanism of unidirectional motion in molecular motors containing a C═N group has been assumed to consist of photoinduced torsion about the double bond. In this work, we present a computational study of the photoisomerization dynamics of a chiral -alkyl imine motor. We find that the location and energetics of minimal energy conical intersections (MECIs) alone are insufficient to understand the mechanism of the motor. Furthermore, a key part of the mechanism consists of out-of-plane distortions of the N atom (followed by isomerization about the double bond). Dynamic effects and out-of-plane distortions are critical to understand the observed (rather low) quantum yield for photoisomerization. Our results provide hints as to how the photoisomerization quantum yield might be increased, improving the efficiency of this class of molecular motors.
光驱动分子马达因其在材料和生物系统中的潜在应用而引起了广泛关注。最近，格雷布和莱恩报道了一类新型分子马达——手性烷基亚胺，它能在光和热的作用下发生单向旋转。含有C═N基团的分子马达中单向运动的机制被认为是由围绕双键的光致扭转组成。在这项工作中，我们对手性烷基亚胺马达的光异构化动力学进行了计算研究。我们发现，仅最低能量锥形交叉点（MECIs）的位置和能量不足以理解马达的机制。此外，该机制的一个关键部分是N原子的面外扭曲（随后是围绕双键的异构化）。动态效应和面外扭曲对于理解观察到的（相当低的）光异构化量子产率至关重要。我们的结果为如何提高光异构化量子产率提供了线索，从而提高这类分子马达的效率。
