Ping-Pong Tunneling Reactions: Can Fluoride Jump at Absolute Zero?

Area of Science:

• Quantum Chemistry
• Supramolecular Chemistry
• Spectroscopy

Background:

• A novel double-germanium fluoride receptor utilizes strong tetrel bonds for halogen binding.
• Fluoride binding creates an asymmetric double-well potential, enabling ion rearrangement.

Purpose of the Study:

• To computationally investigate the mechanism of fluoride rearrangement in the germanium-based receptor at cryogenic temperatures.
• To explore factors influencing the fluoride rearrangement rate, including substituents, solvent polarity, and molecular geometry.

Main Methods:

• Computational chemistry tools were employed to model the fluoride rearrangement.
• Analysis focused on quantum mechanical tunneling as the rearrangement mechanism.
• The impact of electronic and geometric factors on the tunneling barrier was assessed.

Main Results:

• Fluoride rearrangement at cryogenic temperatures proceeds via heavy-atom quantum mechanical tunneling.
• Substituent effects and solvent polarity modulate the tunneling barrier and rate.
• Molecular geometry modifications, particularly barrier width, critically influence tunneling.

Conclusions:

• Quantum tunneling is the operative mechanism for fluoride rearrangement in the designed receptor at low temperatures.
• Experimental validation is proposed using microwave and cryogenic Nuclear Magnetic Resonance (NMR) spectroscopy to confirm fluoride tunneling.