Synthesis and Conformational Analysis of Fullerene Torsion Balances for Assessing the Contribution of Dispersion and Anionic Character in Non‐Covalent Arene–Fullerene Interactions

Abstract

We employ a molecular torsion balance displaying bifurcated conformational isomerism to quantitatively evaluate the non‐covalent interactions between the fullerene surface and substituted arene moieties containing elements with high atomic numbers, as well as the thermodynamic processes involved in the folding equilibrium using nuclear magnetic resonance spectroscopy. The interaction between fullerene and haloaryl groups was stronger in cases where the introduced halogen had a higher atomic number, indicating that dispersion forces play a significant role in the interaction between fullerenes and 4‐haloaryl groups. The dispersion term also significantly contributed to the interaction between fullerene and the 4‐mercaptophenyl group. Moreover, the addition of an appropriate base to the 4‐mercaptophenyl‐appended torsion balance formed the corresponding thiophenolate anion, resulting in a large negative change in the folding free energy in CDCl3. Detailed analysis suggested that the observed attractive anionic arene–fullerene interactions predominantly originated from solvation effects.

Recent advances in supramolecular fullerene chemistry

“…93,94 Fullerenes, which offer a highly symmetric π system devoid of heteroatoms, provide an excellent platform to investigate the importance of polarizability in anion–π catalysis, without the complications of substituents, positive quadrupole moments or in-plane dipoles. 95 Matile and coworkers discovered that a fullerene mono-adduct catalyst 19 exhibited good selectivity for enolate addition and improved the exo / endo diastereoselectivity of the Diels–Alder reaction. 96 Using the anionic [4+2] cycloaddition of dienophile 18 and 3-hydroxy-2-pyrones 17 as an example, strong endo selectivity was observed.…”

Anion–π catalysis on carbon allotropes

“…The use of fullerenes in catalysis is surprisingly underdeveloped [45][46][47][48][49][50][51]. Anion-π and cation-π interactions on fullerenes attract similarly little attention until today [52][53][54][55][56][57]. Anion-π catalysis on fullerenes has been introduced in 2017 [12].…”