Coupled Rocking Motion in a Light-Driven Rotary Molecular Motor

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Nanotechnology

Background:

• Coupled motion is fundamental to natural processes, driving movement and synchronization.
• Molecular motors are artificial machines that mimic biological functions, converting chemical or light energy into mechanical work.

Purpose of the Study:

• To experimentally demonstrate the coupling between the rocking motion of a dihydroanthracene stator and the rotational movement of an overcrowded alkene-based molecular motor.
• To investigate how desymmetrization affects the motor's motion and chirality.
• To explore new methods for controlling molecular motor speed and achieving light-driven rotation.

Main Methods:

• Desymmetrization of an overcrowded alkene-based molecular motor by introducing different alkyl substituents.
• Structural determination of diastereomers using nuclear Overhauser effect spectroscopy (NMR) and single-crystal X-ray analysis.
• Investigation of coupled motion (rotation and oscillation) using proton NMR (¹H NMR) and density functional theory (DFT) calculations.

Main Results:

• Experimental proof of coupled rocking and rotational motion in a molecular motor.
• Identification of two diastereomers with opposite axial chirality.
• Demonstration that motor speed can be regulated by functionalization, influenced by alkyl substituents and their orientation.
• Observation of photo-driven rotation in three out of four steps of the motor's cycle.

Conclusions:

• The study provides novel insights into the coupled motion of molecular motors.
• Desymmetrization offers a strategy to control chirality and study complex movements.
• The findings expand the capabilities of molecular motors, enabling photon-only rotary behavior.