Direct Experimental Evidence for Halogen–Aryl p Interactions in Solution from Molecular Torsion Balances

H. Sun; A. Horatscheck; V. Martos; M. Bartetzko; U. Uhrig; D. Lentz; P. Schmieder*; M. Nazaré*

Angew. Chem. Int. Ed. Engl. 56, 6454 - 6458 (2017); Angew. Chem. 129, 6554 - 6558 (2017)

We dissected halogen–aryl p interactions experimentally using a bicyclic N-arylimide based molecular torsion balances system, which is based on the influence of the non-bonded interaction on the equilibria between folded and unfolded states. Through comparison of balances modulated by higher halogens with fluorine balances, we determined the magnitude of the halogen–aryl p interactions in our unimolecular systems to be larger than -5.0 kJ/mol, which is comparable with the magnitude estimated in the biomolecular systems. Our study provides direct experimental evidence of halogen–aryl p interactions in solution, which until now have only been revealed in the solid state and evaluated theoretically by quantum-mechanical calculations.