The rational design, synthesis and demonstration of the recognition and binding of a diaza-dioxa-12-crown-4 diphosphonate macrocycle to all crystal growth faces of barium sulfate.

Abstract

Computer-aided molecular design and virtual screening of a series of amino phosphonic acid derivatives were used to probe the probable interaction of these compounds as potential crystal growth inhibitors of barium sulfate, as judged by their ability to bind efficiently to all of the possible growing faces. As a result, a diphosphonic acid derivative of a 1,7-dioxa-4,10-diaza-12-crown-4 system 5 was proposed as a potential inhibitor of barium sulfate crystallisation. A subsequent synthesis of this macrocycle was developed, together with other larger-ring oxa-aza crown derivatives. Macrocycle 5 proved to be a highly efficient inhibitor of barium sulfate crystal growth at a level of 0.096 mM, as evidenced by the changes brought about in crystal morphology. Work was therefore undertaken to probe the mechanism of action of 5 using adsorption isotherms, mixed flow reactor and atomic force microscopy (AFM) measurements. It was possible to show that 5 inhibits effectively in solution by covering the growing surfaces, as observed on the 001 surface, effectively inhibiting two-dimensional nucleation as well as monolayer-step growth.