Beyond Size Complementary Factors in Anion–Tetralactam Macrocycle Complexes: From Intrinsic Gas-Phase to Solvent-Predicted Stabilities

The gas-phase affinities of different types of anions X - (halogen anions, oxoanions, and hydrogenated anions) toward a model tetralactam-based macrocycle receptor ( 1 ), defined in terms of stability of an anion-receptor complex ( 1 + X - ) against its disintegration, were evaluated by dissociation studies using a mass spectrometry-based methodology and supported by theoretical calculations (density functional theory-PBE0). The gas-phase complex with Cl - was found to be tailor-made for the macrocycle 1 , while 1 + SA - (SA - = salicylate anion) and 1 + HSO 4 - were the weakest ones. Other complexes displayed a relatively low-stability dispersion (<1.2 kcal·mol -1 ). The 1/ε r approach of the electrostatic contribution scaling method was used to predict the stability trends in a dimethyl sulfoxide solvent from the gas-phase binding energy partition using the symmetry-adapted perturbation theory. High deformation energy and differences in solvation energies were suggested to be the main sources of inconsistency in the predicted and experimental stabilities of 1 + F - and 1 + H 2 PO 4 - complexes.