Structural determination of Cu and Fe-Citrate complexes: theoretical investigation and analysis by ESI-MS

Abstract

The combined use of ESI-MS (electrospray ionization-mass spectrometry) and theoretical calculations for the determination of citrate:metal (metal = Cu and Fe) 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 calculated structures readjusted, from what was originally simulated, since the deprotonation of citric acid differed from what was before simulated. The thermodynamic stability (ΔH(aq.)0) of the complexes optimized at the B3LYP/LANL2DZ level was more exoenergetic than for the complexes found by the PM6 semi-empirical method.