Musa E. Mohamed, Synthesis and Spectroscopic Characterization of l-Aspartic Acid Complexes with Metals of the Lanthanides Family, ILCPA Volume 11, International Letters of Chemistry, Physics and Astronomy (Volume 11)
https://www.scipress.com/ILCPA.11.91
Abstract:
    The complexes between <i>l</i>-aspartic acid and metals of lanthanide series (La<sup>3+</sup>, Pr<sup>3+</sup>, Eu<sup>3+</sup>, Gd<sup>3+</sup>) have been prepared and characterized using a variety of techniques including, infrared spectroscopy, <sup>1</sup>H NMR, <sup>13</sup>C NMR, elemental analysis and metal contents. The sought metal effect on the electronic environment of the chiral carbon and its neighbouring atoms was observed in case of Europium and Praseodymium. The <sup>13</sup>C downfield shift indicates a lower electron density at the carbon with consequent downfield shift observed on the α-H attached to it increasing its acidity.
Keywords:
    IR, Lanthanides (III) Complexes, <i>l</i>-Aspartic Acid, NMR