Preparations and Strucutures of Silver(I) Complexes with<i>cyclo</i>(Glcyl-L-histidyl),<i>cyclo</i>(L-Methionyl-L-histidyl), and<i>cyclo</i>(L-Histidyl-L-histidyl)
The structures of silver(I) complexes with cyclo(glycyl-l-histidyl), cyclo(l-methionyl-l-histidyl), and cyclo(l-histidyl-l-histidyl) were examined using 1H and 13C NMR. The NMR measurements suggest that the silver(I) ion links to the sulfur atom of thioether and the nitrogen atom of imidazole group of the above cyclic peptides, but not to their amide groups.
Co-ordination properties of cyclopeptides. Formation and stability of zinc(II) and copper(II) complexes of histidine-containing cyclopeptides, or imidazole
obtained for the formation of chelate rings of unusual size. The thermodynamic quantities associated with copper(II) complexformation with cyclo(-Gly-His-) were determined. The role of the different stereochemical requirements of copper(II) and zinc(II) in the formation of large chelate rings was assessed by means of previously reported data concerning the copper(II)–cyclo(-His-His-) complexes.