Metal Complexes of Amino Acids. VIII. Carbon-13 Nuclear Magnetic Resonances of Cobalt(III) Complexes Containing l-Aspartic and l-glutamic Acids

Abstract

Abstract The 13C NMR spectra of cobalt(III) complexes containing l-aspartic acid or l-glutamic acid as unidentate, bidentate, or bridged ligand were measured, and the relationship between the coordination types and the changes in chemical shift of carboxyl carbons in these amino acid complexes was discussed. Two structural isomers were newly separated for the trans (O)-[Co en2(l-aspH2 or l-gluH2)2]X3 complex by a column chromatographic method. The structures of the earlier eluted isomers for the trans(O)-[Co en2(l-aspH2)2]X3 and -[Go en2(l-gluH2)2]X3 complexes were assigned to trans(O0) Oγ) and trans(O0, Oδ) (O0, Oγ and Oδ indicate the coordinated oxygen atoms of C0OO, CγOO, and CδOO), respectively, and the structures of the later eluted isomers for the both complexes to trans(O0, O0), on the basis of the shift patterns of carboxyl carbons.