TOC 7b

Suhang He, Frank Biedermann, Nina Vankova, Lyuben Zhechkov, Thomas Heine,

Roy E. Hoffman, Alfonso De Simone, Timothy T. Duignan and Werner M. Nau;

Nat. Chem., 2018, 10, pp 1252-1257.

DOI: 10.1038/s41557-018-0146-0



The accurate dissection of binding energies into their microscopic components is challenging, especially in solution. Here we study the binding of noble gases (He-Xe) with the macrocyclic receptor cucurbit[5]uril in water by displacement of methane and ethane as 1H NMR probes. We dissect the hydration free energies of the noble gases into an attractive dispersive component and a repulsive one for formation of a cavity in water. This allows us to identify the contributions to host-guest binding and to conclude that the binding process is driven by differential cavitation energies rather than dispersion interactions. The free energy required to create a cavity to accept the noble gas inside the cucurbit[5]uril is much lower than that to create a similarly sized cavity in bulk water. The recovery of the latter cavitation energy drives the overall process, which has implications for the refinement of gas-storage materials and the understanding of biological receptors.