Reactivity of contact ion pairs in a charged monotopic receptor
An integrated FT-ICR and computational approach has been employed to investigate the gas phase structure and reactivity of ESI-formed complexes between organic and inorganic acids (HX) and a K+-containing hexaazamacrocycle (M). Two limiting structures are available to those complexes, either the classical [MK+·XH] or the zwitterionic [MH+·K+·X?] one, with the latter prevailing over the first by increasing the gas-phase acidity of the HX ligand.