Interaction of Alkaline Earth Metal Ions with Carboxylic Acids in Aqueous Solutions studied by 13c NMR Spectroscopy

Abstract

13c NMR spectroscopic measurements of aqueous solutions containing alkaline earth metal chloride and a carboxylic acid have been caried out to acquire some insight into the coordination manners of various carboxylic acids to alkaline earth metal ions. The dependence of the 13c NMR signal positions of the carboxylate carbons on the magnesium ion concentration in a magnesium carboxyiate system is a good index to understand the coordination manner of the carboxylate ion. The upfield shift of the car-boxylate carbon signal with increasing magnesium ion concentration indicates that the carboxylate ion acts as a bidentate ligand to form a ring structure. Only in the citrate systems, the existence of a relatively stable complex is evidenced in which the citrate ion is expected to act as a tridentate ligand. © 1998, Verlag der Zeitschrift für Naturforschung. All rights reserved.