No abstract

Spectrometric and theoretical tools have been employed in this study in order to elucidate the structures of DTPA (diethylenetriaminepentaacetic acid) complexed to copper and lead. Mass spectrometry allowed determining the 1:1 stoichiometry of metal:ligand, while infrared spectroscopy demonstrated that both N and O are sites for complexation. 13 C NMR analysis showed the existence of free and complexed carboxyl groups, due to a straight singlet at 180.7 ppm (free carboxylic 13 C) and to a broad signal at 179.3 ppm (complexed carboxylic 13 C, 2 J Pb…O=C ). A distorted NMR signal were observed for the Cu-DTPA carboxyl group, due to the Cu 2+ paramagnetism. Based on the spectrometric evidences for the metal-DTPA structures, DFT optimizations were carried out and an octahedral-like arrangement for the Cu complex and a ''shell-like'' arrangement for the Pb complex, both hexacoordinated, were then proposed for the structures of the titled compounds.