Solvent-Driven Modulation of Shuttling Dynamics in an Autonomous Chemically Fueled Information Ratchet

Area of Science:

• Supramolecular Chemistry
• Computational Chemistry
• Materials Science

Background:

• Artificial molecular machines require precise control over their dynamics.
• The influence of solvation on molecular machine performance is not well understood.
• Understanding solvation effects is crucial for designing advanced molecular systems.

Purpose of the Study:

• To investigate how solvent properties affect the energy landscapes and kinetics of molecular machines.
• To explore the distinct thermodynamic and kinetic regimes governing macrocycle motion in a [2]rotaxane.
• To provide a molecular-level framework for understanding solvation-driven behavior in molecular machines.

Main Methods:

• Utilized well-tempered and infrequent metadynamics simulations.
• Investigated equilibrium shuttling in a minimal [2]rotaxane.
• Systematically varied solvent polarity and hydrogen-bonding capacity.

Main Results:

• Identified distinct thermodynamic and kinetic regimes based on solvent properties.
• Observed symmetric macrocycle distribution in polar, H-bond-accepting solvents, with competing enthalpic and entropic forces.
• Found entropically biased single-station occupancy in low-polarity, H-bond-donating solvents due to axle conformational collapse.
• Characterized solvent-dependent asymmetries and ruggedness in transition pathways despite similar free-energy barriers.

Conclusions:

• Solvation plays a critical role in dictating the passive ratchet behavior of molecular machines.
• The study provides strategic insights for designing high-performance molecular machines tailored to specific solvent environments.
• Findings offer a molecular-level understanding of how environmental factors influence artificial molecular systems.