Four generations of water-soluble dendrimers with 9 to 243 benzoate tethers: Synthesis and dendritic effects on their ion pairing with acetylcholine, benzyltriethylammonium, and dopamine in water

Water-soluble benzoate-terminated dendrimers of four generations (from G(0) with 9 branches to G(3) with 243 branches) were synthesized and fully characterized. They form water-soluble assemblies by ion-pairing interactions with three cations of medicinal interest (acetylcoline, benzyl-triethylammonium, and dopamine), which were characterized and investigated by (1)H NMR spectroscopy, where-as such interactions do not provoke any significant shift of (1)H NMR signals with the monomeric benzoate anion. The calculated association constants confirm that the dendritic carboxylate termini reversibly form ion pairs aggregates. Diffusion coefficients hydrodynamic diameters of the and and dendrimers, as well as changes thereof on interaction with the cations, were evaluated by DOSY experiments. The lack of increase of dendrimer size on addition of the cations and the upfield shifts of the (1)H NMR signals of the cation indicate encapsulation within the hydrophobic dendrimer interiors together with probable backfolding of the benzoate termini.