Light-Driven Supramolecular Pumping by Changing Shape Complementarity.

Area of Science:

• Supramolecular Chemistry
• Molecular Machines
• Nanotechnology

Background:

• Cell membrane protein pumps actively transport solutes against gradients, crucial for biological energy conversion.
• These pumps utilize light or chemical energy to establish nonequilibrium steady states.
• Creating directed motion in artificial molecular systems presents significant challenges.

Purpose of the Study:

• To engineer a molecular system capable of sustained unidirectional substrate transport.
• To utilize light energy for controlled movement within an artificial molecular construct.
• To explore energy ratcheting mechanisms for molecular translocation.

Main Methods:

• Fabrication of a molecular axle with distinct termini and a photoswitchable macrocyclic ring.
• Exploiting differential shape complementarity between axle termini and ring isomers.
• Modulating kinetic barriers for ring slippage via light-induced interconversion of ring isomers.
• Achieving unidirectional axle translation under steady-state irradiation.

Main Results:

• Demonstrated repeated, unidirectional transit of the molecular axle through the macrocyclic ring.
• Established an energy ratcheting mechanism driven by light to control translocation.
• Observed enhanced photoconversion due to the bound axle, contributing to system directionality via information ratcheting.
• Achieved effective and continuous unidirectional translation of the axle relative to the ring.

Conclusions:

• Developed a light-driven molecular machine that achieves continuous unidirectional motion.
• The energy ratcheting mechanism effectively controls molecular transport.
• This work offers a pathway toward artificial substrate pumping for generating electrochemical gradients.
• Potential applications in biomimetic systems and nanotechnology.