Cylodextrins effects in the substitution reaction of 4,4′-bpy for the aquo ligand in aquopentacyanoferrate (II): An estimation of the binding constants of the reactant and the transition state to cyclodextrins

The substitution reaction of 4,4′-bpy (4,4′-bipyridine) for the aquo ligand in aquopentacyanoferrate (II) was studied in solutions containing α-, β- and γ-cyclodextrins. We conclude that the well-known pseudophase model is equivalent to the Brönsted equation in regard to the interpretation of the cyclodextrins effects on reactivity. The equivalence follows from the fact that both pseudophase and Brönsted approaches can be used to rationalize kinetic data and permit to quantify the inclusion of the aromatic ligand in the cyclodextrins.