Force-conductance spectroscopy of a single-molecule reaction

Area of Science:

• Molecular Biophysics
• Chemical Physics
• Computational Chemistry

Background:

• Single-molecule reactions are crucial for understanding chemical processes.
• Mechanically activated reactions offer unique control over chemical transformations.
• Monitoring reaction intermediates requires advanced measurement techniques.

Purpose of the Study:

• To demonstrate the combined use of force and conductance measurements for tracking single-molecule reactions.
• To investigate mechanically activated cis-to-trans isomerization reactions.
• To resolve reaction intermediates and non-reactive events at the single-entity limit.

Main Methods:

• Simulated force-conductance profiles of cyclopropane oligomers using molecular dynamics and reactive force fields.
• Calculated conductance via Landauer transport and nonequilibrium Green's function methods.
• Analyzed mechanical elongation and cis-to-trans isomerization events.

Main Results:

• Simultaneous force and conductance measurements successfully monitored step-by-step reaction progress.
• Conductance profiles resolved reaction intermediates not distinguishable by force alone.
• Force signals provided information on non-reactive backbone deformations, invisible in conductance.
• Results were robust across different electrode and Hamiltonian models.

Conclusions:

• Integrating covalent mechanochemistry with molecular conductance enables detailed investigation of chemical reactivity.
• This combined approach offers unprecedented insight into single-molecule reaction dynamics.
• The methodology holds potential for advancing the study of chemical transformations at the single-entity limit.