Understanding the Nature and Strength of Noncovalent Face-to-Face Arene-Fullerene Interactions

Face-to-face noncovalent arene-fullerene interactions are important in several research fields such as synthetic chemistry, materials chemistry, and medicinal chemistry; however, their nature and strength are still poorly understood. In this study, we prepare a fullerene-based torsion balance containing thioanisole, phenol, naphthalene, azulene, and pyrene moieties as a unimolecular model system. Moreover, we compare the folding free energies between the folded and the unfolded conformers of a series of the molecular torsion balances to quantify noncovalent interactions between arenes and the fullerene surface. This work demonstrates that the contributions of polarizabilities, anionic charges, electronic dipole moments, and the number of arene rings to the interactions can be experimentally measured by analyzing the folding equilibrium of the molecular torsion balances.