A molecular balance for measuring aliphatic CH-π interactions
A series of conformationally flexible bicyclic N-arylimides were employed as molecular balances to study the weak aliphatic CH-π interaction between alkyl and arene groups. The formation of intramolecular CH-π interactions in the folded conformers was characterized by X-ray crystallography. The strengths of the interactions were characterized in CDCl3 by the changes in the folded/unfolded ratios, as measured by 1H NMR. The CH-π interaction between a methyl group and an aromatic surface was ~1.0 kcal/mol and was easily disrupted or masked by conformational entropy and repulsive steric interactions.
Carroll, William R.,Zhao, Chen,Smith, Mark D.,Pellechia, Perry J.,Shimizu, Ken D.