Competitive interactions of two ion-paired salts with a neutral host to form two non-ion-paired complexes.

It is demonstrated that our reported equilibrium treatments that take into account ion-paired guest and non-ion-paired complexes can be applied to competitive complexations. Satisfactory results were obtained for a system with two cationic guests [N,N'-dimethyl-4,4'-biyridinium bis(hexafluorophosphate) (1) and dibenzylammonium hexafluorophosphate (2)] having a common counterion and a single neutral host dibenzo-24-crown-8 (3), even though for this system one exchange process is slow and the other fast on the 1H NMR time scale. The competitive complexation protocol presented here provides a convenient method for the determination of KapKipd (the product of the ion-pair dissociation constant of the guest salt and the association constant for the host with the resultant free cation) for new systems from ion-paired guests that form complexes that are not ion paired.