Direct Observation of Electric-Field-Catalyzed Imine Cleavage by Single-Molecule Conductance

Area of Science:

• Chemical dynamics
• Materials science
• Physical chemistry

Background:

• Controllable cleavage of imine bonds is crucial for dynamic covalent chemistry.
• Achieving this under controlled ultrahigh electric fields (UEF) is experimentally challenging.

Purpose of the Study:

• To investigate the effect of UEF on imine bond cleavage using a single-molecule approach.
• To explore the mechanism and influencing factors of UEF-induced bond cleavage.

Main Methods:

• Utilized the scanning tunneling microscopy break junction (STM-BJ) technique.
• Applied a tunable UEF (∼10^9 V/m) to imine bonds in solution.
• Monitored bond cleavage via single-molecule conductance measurements.

Main Results:

• Imine bonds showed negligible cleavage under field-free conditions.
• UEF significantly promoted imine bond cleavage in both polar and nonpolar solvents.
• Kinetic studies revealed dependence on solvent polarity and electric field strength.

Conclusions:

• UEF effectively lowers the energy barrier for imine bond cleavage via cooperative hydrolysis.
• Provides direct evidence and a strategy for manipulating dynamic covalent bonds using electric fields.