In this study, we have advanced the field of light-driven molecular rotary motors (LDMRMs) by achieving two pivotal goals: lowering the thermal helix inversion (THI) barrier and extending the absorption wavelength into the visible spectrum. This study involves the structural reengineering of a second-generation visible LDMRM, resulting in the synthesis of a novel class, specifically, 2-((2S)-5-methoxy-2-methyl-2,3-dihydro-1H-cyclopenta[a]naphthalen-1-yl)-3-oxo-2,3-dihydro-1H-dibenzo[e,g]indole-6,9-dicarbonitrile. This redesigned motor stands out with its two photoisomerization stages and two thermal helix inversions, featuring exceptionally low THI barriers (4.00 and 2.05 kcal mol⁻¹ at the OM2/MRCI level for the EM → EP and ZM → ZP processes, respectively). Moreover, it displays absorption wavelengths in the visible light range (482.98 and 465.76 nm for the EP and ZP isomers, respectively, at the TD-PBE0-D3/6-31G(d,p) level), surpassing its predecessors in efficiency, as indicated by the narrow HOMO–LUMO energy gap. Ultrafast photoisomerization kinetics (approximately 0.8–1.6 ps) and high quantum yields (around 0.3–0.6) were observed through trajectory surface hopping simulations. Additionally, the simulated time-resolved fluorescence emission spectrum indicates a significantly reduced “dark state” duration (0.09–0.26 ps) in these newly designed LDMRMs compared to the original ones, marking a substantial leap forward in the design and efficiency of LDMRMs.

中文翻译：

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光驱动分子旋转电机的先进理论设计：增强热螺旋反转和可见光激活


在这项研究中，我们通过实现两个关键目标推进了光驱动分子旋转电机（LDMRM）领域的发展：降低热螺旋反转（THI）势垒并将吸收波长扩展到可见光谱。这项研究涉及第二代可见 LDMRM 的结构重组，从而合成了一个新的类别，特别是 2-((2S)-5-甲氧基-2-甲基-2,3-二氢-1H-环戊二烯。 a]萘-1-基)-3-氧代-2,3-二氢-1H-二苯并[e,g]吲哚-6,9-二甲腈。这款重新设计的电机以其两个光异构化阶段和两个热螺旋反转而脱颖而出，具有极低的 THI 势垒（在 EM → EP 和 ZM → ZP 工艺的 OM2/MRCI 水平上为 4.00 和 2.05 kcal mol ⁻¹ ， 分别）。此外，它在可见光范围内显示出吸收波长（TD-PBE0-D3/6-31G(d,p)级别的EP和ZP异构体分别为482.98和465.76 nm），在效率上超越了其前辈，正如狭窄的 HOMO-LUMO 能隙所示。通过轨迹表面跳跃模拟观察到超快光异构化动力学（大约 0.8-1.6 ps）和高量子产率（大约 0.3-0.6）。此外，模拟的时间分辨荧光发射光谱表明，与原始设计相比，这些新设计的 LDMRM 的“暗态”持续时间（0.09-0.26 ps）显着缩短，标志着 LDMRM 的设计和效率取得了实质性飞跃。