Theoretical and experimental investigation of complex structures citrate of zinc (II)

The combined use of ESI-MS and theoretical calculations for the determination of zinc: citrate structures are reported. Mass spectrometry allowed to determine the stoichiometry 1:1 and 2:1 of the complexes, corroborating the theoretical calculations. The species found in the ratio 2:1 had their molecular structures readjusted, since the deprotonation of citric acid differed from what was simulated. The thermodynamic stability (Delta H-(aq.)(0)) of the complexes optimized at the B3LYP/LANL2DZlevel was more exoenergetic than for the complexes found by the PM6 semi-empirical method. (C) 2014 Elsevier B.V. All rights reserved.