Factors influencing anion binding stoichiometry : the subtle influence of electronic effects

Six new, charge-neutral norbornene-based receptors 1a,1b– 3a,3b were prepared, and their ability to interact with simple anions in DMSO was investigated using 1H NMR and UV/ Vis spectroscopy. Binding of dihydrogenphosphate by the six receptors appeared to be based solely on steric constraints. In contrast, the binding stoichiometry of 3a and 3b to acetate was controlled by subtle electronic factors.