ΔG° and TΔS° charge relationships for the binding of carboxylic anions by open-chain polyammoninm cations

Enthalpies of formation have been determined by titration calorimetry for complexes formed by some polycarboxylic anions (citrate, 1,2,3-propanetricarboxylate, 1,2,3,4-butanetetracarboxylate) with open-chain polyammonium cations C2(n-1)NnH(6n-2)(n+) (n = 2-6), at 25 degrees C. Delta H degrees values are generally positive and, therefore, these complexes are entropically stabilized. Delta G degrees and T Delta S degrees follow a linear trend as a function of polyammonium cation and carboxylic anion charges. The linear dependence on charges of Delta G degrees is the same for different systems, whilst that of T Delta S degrees is specific for each system. Delta G degrees and T Delta S degrees charge relationships are reported.