A potentiometric study of the effects of molecular complexing on acid–base equilibria

Abstract

The effect of molecular complexing on several acid–base equilibria involving organic π donor acids has been studied by a potentiometric method. The method leads to complexation constants for the acceptor with the donor acid and its conjugate base. In several cases the two association constants can be determined with sufficient precision to obtain an estimate of the acidity constant for the 1:1 acceptor–donor acid complex. In all situations where charge-transfer and electrostatic interactions are expected to have opposing effects on the acidity, electrostatic effects dominate. The range of the validity and usefulness of the potentiometric method in studies of molecular complexation equilibria is discussed, together with the results obtained in this work.