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

ABSTRACT

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.

ACKNOWLEDGMENT

This project was supported by the National Natural Science Foundation in China (29975012). The authors acknowledge the helpful and constructive comments of the referees.