Elucidating the ring inversion mechanism(s) for biscalixarenes.

Area of Science:

• Supramolecular Chemistry
• Computational Chemistry
• Materials Science

Background:

• Biscalix[4]arenes (biscal) are derived from calix[4]arenes and serve as precursors for polymetallic clusters.
• These clusters have potential applications in data storage as single-molecule magnets.
• Polymetallic clusters involving biscal require octadentate binding and ring inversion.

Purpose of the Study:

• To elucidate the mechanism of biscalix[4]arene ring inversion using density functional theory (DFT).
• To identify and analyze various energy pathways for full and partial ring inversion.
• To determine the lowest energy pathway and its associated barrier height.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Analysis of fourteen possible pathways for full inversion, including transition states.
• Solvent effect optimizations using PCM and CPCM solvent models.

Main Results:

• The lowest energy pathway for full inversion was identified with a barrier height of 19.31 kcal mol(-1).
• DFT calculations mapped the entire potential energy surface for the ring inversion process.
• Long-range solvent effects were found to be relatively unimportant.

Conclusions:

• This study provides the first comprehensive DFT elucidation of the biscalix[4]arene ring inversion mechanism.
• Understanding this inversion is key to designing and synthesizing novel polymetallic clusters.
• The findings contribute to the development of advanced materials for applications like data storage.