Structural determination of Zn and Cd-DTPA complexes: MS, infrared, (13)C NMR and theoretical investigation.
The joint application of MS, infrared and (13)C NMR techniques for the determination of metal-DTPA structures (metal=Zn and Cd; DTPA=diethylenetriaminepentacetic acid) is reported. Mass spectrometry allowed determining the 1:1 stoichiometry of the complexes, while infrared analysis suggested that both nitrogen and carboxyl groups are sites for complexation. The (13)C NMR spectrum for the cadmium-containing complex evidenced the existence of free and complexed carboxyl groups, due to a straight singlet at 179.0 ppm (free carboxylic (13)C) and to two broad singlets or a broad doublet at 178.3 ppm (complexed carboxylic (13)C, (2)J(Cd-C(=O))=45.2 Hz). A similar interpretation might be given for the zinc derivative and, with the aid of DFT calculations, structures for both complexes were then proposed.
Silva
Vanézia L
VL
Departamento de Química, Universidade Federal de Lavras (UFLA), Lavras, MG, Brazil.
Carvalho
Ruy
R
Freitas
Matheus P
MP
Tormena
Cláudio F
CF
Melo
Walclée C
WC
D002104:Cadmium / Q000737:chemistry*; D002247:Carbon Isotopes; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D004369:Pentetic Acid / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics; D014732:Vibration; D015032:Zinc / Q000737:chemistry*
D002247:Carbon Isotopes; D002104:Cadmium; D004369:Pentetic Acid; D015032:Zinc