Synthesis and Relaxivity of α-Oxo-γ-Ethoxycarbonylbutanoic Acid Thiosemicarbazone Rare Earth Complexes

The rare earth metal complexes of α-oxo-γ-ethoxy carbonylbutanoic acid thiosemicarbazone (HEAT) have been synthesized in the template reaction when LnCl3·nH2O was added to the system dissolved α-oxopentanedioic acid and thiosemicarbazide in anhydrous ethanol and refluxed on a water bath. Although α-oxopentanedioic acid thiosemicarbazone (H2PAT) can be synthesized in the system without LnCl3·nH2O, HEAT cannot be formed under analogous conditions. This proves that the compounds LnCl>3·nH2O have a catalytic effect on the esterification reaction. The composition and nature of the complexes are characterized by elemental analyses, thermal analyses, UV, IR, and 1H NMR spectra. In addition, the relaxivity (R1) of the Gd-complex has been determined by the INVLNC.Au program using inversion recovery pulse sequences, R1=8.10 mmol·L−1·s−1.