Complex formation of selected trivalent metal ions with (4R)-thiazolidine-4-carboxylic acid and some of its derivatives

The complex formation of Al(III), Ga(III), In(III), Fe(III), La(III), and Ce(III) with (4R)-thiazolidine-4-carboxylic acid (TCA) and some of its 2-alkyl/aryl-substituted derivatives in aqueous solutions at ionic strength I = 0.1 mol dm(-3) (NaCl) and temperature theta = 25 degrees C was studied using the potentiometric titration method. The satisfying results were attained only for Al(III), Ga(III), and In(III) in reaction with TCA and its 2-alkyl-substituted derivatives. Other M(III) tested did not allow to evaluate their complex stability constants because of the precipitate creation or poor interaction. Further it was found that 2-aryl- or 2,2-dimethyl-substituted TCA derivatives are rapidly changed in aqueous solutions resulting in impossibility to determine their correct dissociation constants and hence to quantify the complex formation constants.