The study of the anion recognition mechanisms, playing a crucial role in bio- and environmental chemistry, has been developed more slowly than the cation counterpart. Indeed, anions can have a wide variety of molecular geometries that increases the difficulty in designing a specific receptor. The anion coordination chemistry is mainly based on the non covalent stabilization due to N-H, C-H groups, and in a certain amount to the underexplored interactions such as anion-p and halogen bonding. Many efforts have been done to develop experimental and theoretical methodologies aimed to investigate the nature and the intensity of non covalent interactions involved in the stabilization of supramolecular assemblies. However, the knowledge of their intrinsic features needs a gas-phase experimental approach, in order to rule out any environmental effect. Intra- and intermolecular interactions fully develop in the gas phase, where the study of the conformational freedom and of the intrinsic binding properties is a challenging task. In the present project, a multi-dimensional mass spectrometric (MS) platform will be dedicated to the investigation of several potassium-containing complexes [Z·H·K·A]+ formed between a protonated in-house synthesized hexaazamacrocycle (Z) and the anion of organic and inorganic acid (HA): the kinetics of ligand exchange reaction (ESI-FT-ICR-MS) and the collisional cross section (ion-mobilty MS) of different [Z·H·K·A]+ adducts will be measured. The presence of four chirogenic centres in the Z structure will provide a further three-dimensional probe. Indeed, the meso-form and the RRRR- and SSSS-macrocycle could have a different folding induced by a different intra-molecular hydrogen bond network. All the experimental results will be supported by the a proper theoretical approach that will simulate the investigated complexes in both the gas and the condensed phase.
