Structural determination of Zn and Cd-DTPA complexes: MS, infrared, (13)C NMR and theoretical investigation |
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Authors: | Silva Vanézia L Carvalho Ruy Freitas Matheus P Tormena Cláudio F Melo Walclée C |
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Institution: | Departamento de Química, Universidade Federal de Lavras (UFLA), Lavras, MG, Brazil. |
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Abstract: | 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. |
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Keywords: | Zn/Cd complexes DTPA MS Infrared 13C NMR DFT calculations |
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