Light-driven molecular motors that perform targeted rotary movements have great potential for future applications in nanotechnology. In order for such motors to be used as drives, they must be integrated into larger molecular units and their mechanical movements transferred to nanomachines – currently a major challenge for scientists. LMU researcher Henry Dube and his team have now taken an important step along this path: The scientists were able to couple a motor with a receiver unit and thus significantly accelerate their rotation.

The molecular motor is based on the molecule hemithioindigo, which has a carbon double bond. Under the influence of light the molecule changes its structure and rotates unidirectionally around its double bond. “In a work published in 2018, we already succeeded in combining this double bond with a single bond in a second part of the molecule, as if with a molecular rope,” says Dube. “Although this single bond also rotates on its own due to heat, the coupling enabled us to transfer the direction of motion, i.e. we forced the bond to rotate in only one direction.”
It was still unclear, however, whether the motor really drives the movement of the second binding and not only steers its direction. Therefore, the scientists have now installed a brake that prevents the single bond from rotating by itself under experimental conditions – the motor must therefore work against the brake to make the single bond rotate. “In this way, we were able to prove that the motor really does accelerate the rotation of the single bond – by several orders of magnitude,” says Dube.
Overall, the scientists believe that the results provide unprecedented insights into the mechanism of an integrated molecular machine. In addition, the potential energy usable in the system can be quantified. The current results therefore provide initial answers to the question as to how much work a single molecular motor can actually do on the molecular scale. “A next milestone will be to use the transferred energy to carry out work at the molecular level,” says Dube.

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