Light gear transmission Nature Chemistry

This article proposes a new concept of using energy driven molecular gears. Using visible light as the energy source, HTI actively promotes different gear transmission processes at the nanoscale.
Unlike hot gear transmission, light gear transmission is the dominant movement within the molecular framework. Meanwhile, the conversion of 180 ° double bond isomerization to 120 ° single bond rotation is achieved through the use of a bevel gear mechanism, which exhibits highly challenging precise movement (two to three steps at full rotation) and spatial reorientation of dynamic motion (120 ° angle).

Figure 1. Comparison of reported molecular gear transmission systems and synchronous motion with optical gear transmission

Key point: The reported functional gear transmission systems are not directly driven by energy, and their motion is the result of thermal fluctuations. Optical gear transmission is an effective method for achieving active gear motion at the molecular scale.

Figure 2. HTI optical gear and its thermal activation motion

Key point 1: Under thermal activation, the single bond rotation (SBR) of the triplene fragment in the dark will lead to the mutual conversion between isomers A and rac-B or isomers C and rac-D.
Key point 2: Under thermal activation, there is only sliding motion around the triplene axis, and there is no coupled gear motion between the triplene and thioindigo fragments.

Figure 3. Optical gear transmission behavior in HTI optical gears
Key point 1: The results of Markov matrix dynamics analysis clearly demonstrate the significant photo gear effect of Z-type and E-type isomers. In the isomers C and rac-D of E-type, the photoelectric effect is more pronounced and the sliding motion is significantly reduced. Especially for isomer C, optical gear transmission is actually its main process.

Key point 2: Sliding motion dominates in Z-isomers, leading to significant single double bond isomerization (DBI) and SBR in isomers A and rac-B. However, a clear tendency towards photoelectric motion was also observed, with the central double bond and adjacent single bond connected to the triaidene fragment rotating simultaneously by 180 ° and 120 °, respectively.

Key point 3: The initial geometric structure has a significant impact on the effectiveness of optical gear transmission, and the significant photoelectric selectivity of E-type isomers can be partially attributed to the better meshing of carbonyl groups in the triaidene capsules. For Z-type isomers, it can be explained as poor meshing established by sulfur atoms between thioindigo and triphenylene fragments. However, electronic effects may also play an important role, as the spatial resistance and meshing in optical gears are clearly not sufficient to have any impact on thermal transmission.

This article presents a unique and powerful concept, namely optical gear transmission, which is used to actively promote precise conversion of molecular motion. Through optical transmission, light can be used as an external energy source to establish effective and active transmission motion at the nanoscale. This work provides a unique method for manipulating precise molecular motion and opens up new possibilities and design concepts for creating future integrated nanomachines.

Original link: https://doi.org/10.1038/s41557-022-00917-0