Chloride Binding by Polyammonium Receptor Molecules: 35Cl‐NMR Studies

Binding of chloride anion by protonated polyamines was investigated by 35ClNMR spectroscopy. The presence of protonated macro(poly)cyclic polyamines caused downfield shifts and significant line broadening of the 53ClNMR signals. 35ClNMR spectroscopy was used for complex-formation stoichiometry determination and revealed the formation of a binuclear chloride complex with the fully protonated ditopic hexaazamacrocyclic receptor 6. 35ClNMR spectroscopy was also applied in competition experiments between Cl and SO42− and demonstrated that the fully protonated macrocyclic hexaamine 4 forms a strong complex with SO4−2 with 1:1 stoichiometry.