Engineering switchable rotors in molecular crystals with open porosity

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Crystallography

Background:

• Porous molecular crystals offer tunable environments for molecular interactions.
• Controlling molecular dynamics within crystalline structures is key for advanced materials.

Purpose of the Study:

• To present the first example of a porous molecular crystal incorporating functional rotors.
• To investigate the influence of guest molecules on rotor dynamics and material properties.

Main Methods:

• Synthesis of a novel porous molecular crystal with rotor-bearing molecular rods.
• Characterization of crystal structure and porosity.
• Variable-temperature solid-state Nuclear Magnetic Resonance (NMR) spectroscopy to study rotor dynamics.
• Gas sorption experiments (CO2, I2).

Main Results:

• A permanently porous crystal structure was successfully synthesized and characterized.
• The molecular rotors exhibited high-frequency dynamics (10^8 Hz at 240 K).
• Rotor dynamics were reversibly switched off and on by iodine (I2) absorption and desorption.
• The crystal channels effectively absorbed CO2 and I2 vapors at low pressures.

Conclusions:

• The study demonstrates a novel porous material with switchable molecular dynamics.
• The material's response to guest molecules suggests potential applications in sensing and pollutant management.
• This work opens avenues for designing responsive crystalline materials based on molecular rotors.