Metal Complexes of Aspartic Acid and Glutamic Acid

Aspartic acid (I) and glutamic acid (II) both have three binding sites for protons or metal ions. Chelation of the amino and https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003573586/c85db6d8-3155-491c-803c-0f6baac3eae1/content/fig0003.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> α-carboxylate groups occurs readily, and much of the study of metal binding has been devoted to attempts to deduce whether the side chain carboxylates are also coordinated to the metal ion. Three chelate rings are formed when these ligands are tridentate, one glycine-1ike five-membered ring and rather unusual six-, seven-, or eight-membered rings. The majority of convincing reports suggest that aspartate will usually be tridentate whereas no well-established case of mononuclear complexes with tridentate glutamate has been reported. Although to date crystal structures of glutamate complexes have invariably shown bridging of two or even three metal ions, the possibility of polymerization has been little considered in solution studies. A few cases of binding or chelation not involving the amine group have been reported.