Direct Experimental Evidence for Halogen-Aryl π Interactions in Solution from Molecular Torsion Balances

Angew Chem Int Ed Engl. 2017 Jun 1;56(23):6454-6458. doi: 10.1002/anie.201700520. Epub 2017 Apr 28.

Abstract

We dissected halogen-aryl π 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 π interactions in our unimolecular systems to be larger than -5.0 kJ mol-1 , which is comparable with the magnitude estimated in the biomolecular systems. Our study provides direct experimental evidence of halogen-aryl π interactions in solution, which until now have only been revealed in the solid state and evaluated theoretically by quantum-mechanical calculations.

Keywords: halogen bonding; halogen-aryl π interactions; molecular balances; molecular recognition; residual dipolar coupling.