Contact ion pairs on a protonated azamacrocycle: the role of the anion basicity

A potassium-containing hexaazamacrocyclic dication, [M•H•K](2+), is able to add in the gas phase mono- and dicarboxylate anions as well as inorganic anions by forming the corresponding monocharged adducts, the structure of which markedly depends on the basicity of the anion. With anions, such as acetate or fluoride, the neutral hexaazamacrocycle M acts as an acceptor of monosolvated K(+) ion. With less basic anions, such as trifluoroacetate or chloride, the protonated hexaazamacrocycle [M•H](+) performs the unusual functions of an acceptor of contact K(+)/anion pairs. Graphical Abstract ᅟ.