Solvent effects and driving forces in pillararene inclusion complexes.

Area of Science:

• Supramolecular Chemistry
• Host:Guest Chemistry
• Macrocyclic Chemistry

Background:

• Pillararenes are novel aromatic macrocycles forming inclusion complexes.
• The driving forces of pillararene complexation, especially solvent effects, are not well understood.

Purpose of the Study:

• To investigate the role of solvent in pillararene host:guest complexation.
• To identify key factors governing binding thermodynamics and affinities.

Main Methods:

• Experimental measurement of binding thermodynamics for model complexes in various solvents.
• Computational chemistry to rationalize experimental data and elucidate complexation mechanisms.

Main Results:

• Electrostatic complementarity between host cavity and guest molecule is crucial.
• Polar guests exhibit reduced binding in polar solvents due to competitive solvation.
• Solvent molecular shape significantly influences binding by affecting cavity accessibility.
• A solvent change from acetonitrile to o-xylene increased binding affinity by over four orders of magnitude.

Conclusions:

• Solvent-host and solvent-guest interactions are critical for pillararene complexation.
• Solvent selection is paramount in designing effective molecular host:guest systems.
• Understanding these interactions enables rational design of macrocyclic hosts with tunable affinities.