Beyond Single-Cycle Autonomous Molecular Machines: Light-Powered Shuttling in a Multi-Cycle Reaction Network

Area of Science:

• Molecular Machines
• Supramolecular Chemistry
• Chemical Kinetics

Background:

• Biomolecular machines convert energy for function, moving systems from equilibrium using complex reaction networks.
• Characterizing kinetic asymmetry in these networks is challenging.
• Existing synthetic systems with quantified kinetic asymmetry use simple, single-cycle networks.

Purpose of the Study:

• To report a novel light-driven [2]rotaxane enabling autonomous synthetic molecular machine operation.
• To demonstrate a multi-cycle chemical reaction network in a synthetic system.
• To quantify kinetic asymmetry in a multi-cycle network for the first time.

Main Methods:

• Design and synthesis of a photoactive [2]rotaxane with a macrocycle exhibiting differential photoreactivity.
• Utilizing E to Z isomerization to alter macrocycle affinity for binding sites on the axle.
• Applying advanced theoretical methods to quantify kinetic asymmetry in the multi-cycle network.

Main Results:

• Demonstrated autonomous operation of a synthetic molecular machine via a multi-cycle network.
• Achieved the simplest rotaxane to date capable of autonomous shuttling.
• Successfully quantified kinetic asymmetry in a multi-cycle system, a first in the field.

Conclusions:

• The developed [2]rotaxane represents a significant advancement in synthetic molecular machines.
• This work provides a general strategy for creating and quantifying kinetic asymmetry in multi-cycle systems.
• The findings pave the way for more complex and efficient synthetic molecular machines.