Solvation rules: aromatic interactions outcompete cation-π interactions in synthetic host-guest complexes in water.

Chemical double mutant cycles were used to measure the interaction of a N-methyl pyridinium cation with a π-box in a calix[4]pyrrole receptor. Although the cation-π interaction is attractive (-11 kJ mol-1), it is 7 kJ mol-1 less favourable than the corresponding aromatic interaction with the isosteric but uncharged tolyl group.Herchel Smith fund, Gobierno de España MICINN/AEI/FEDER (PID2020-114020GB-I00 and CEX2019- 000925-S), the CERCA Programme/Generalitat de Catalunya, and AGAUR (2017 SGR 1123