Azotriptycenes: Photoswitchable Molecular Brakes

Area of Science:

• Molecular Machines
• Supramolecular Chemistry
• Photochemistry

Background:

• Controlling molecular motion is key for developing molecular machines.
• Molecular brakes are essential components that decelerate specific molecular movements upon external stimuli.
• Azotriptycenes offer a novel structural framework for light-responsive molecular brakes.

Purpose of the Study:

• To introduce azotriptycenes as a platform for light-controlled molecular brakes.
• To investigate the kinetics of molecular motion within azotriptycenes and how they change upon photoisomerization.
• To provide mechanistic insights for designing advanced molecular brakes.

Main Methods:

• Utilized a combination of theoretical calculations and variable temperature Nuclear Magnetic Resonance (NMR) spectroscopy.
• Analyzed the intrinsic kinetics of C-N bond rotation in azotriptycenes.
• Studied the effect of photoisomerization on these rotational rates.

Main Results:

• Azotriptycenes enable reversible control over C-N bond rotation rates, with changes spanning up to five orders of magnitude.
• The rate modulation is highly localized, with the most significant effects observed at the C-N bond linking the triptycene rotor to the diazo group.
• Detailed mechanistic understanding of the isomerization-induced kinetic changes was achieved.

Conclusions:

• Azotriptycenes serve as effective light-controlled molecular brakes.
• The observed reversible deceleration and acceleration of molecular motion provide a powerful tool for molecular control.
• These findings lay the groundwork for the rational design and future applications of sophisticated molecular devices.