EXAFS and XANES studies of Ni(II), Zn(II), Mn(II) and Ag(I) complexes of some 2-(polyhydroxyalkyl)thiazolidine-4-carboxylic acids

Nine Ni(II), five Zn(II) and Mn(II) and three Ag(I) complexes of selected 2 (polyhydroxyalkyl)thiazolidine-4-carboxylic acids (PHTAc) were prepared in the solid state. The analytical data showed that complexes containing Ni(II ), Zn(II), Mn(II) and Ag(I) ions and ligands in molar ratios of 1:2 and 1:1 are formed. The IR data revealed that the first three of these metal ions are coordinated to the ligand via {N,O} and the Ag(I) via {S,N} donor atoms . Their local structures were determined by the extended X-ray absorption f ine structure (EXAFS) method. The results indicated the octahedral structur es of the Ni(II) and Mn(II) complexes, with mean Ni-O,N and Mn-O,N distance s of 202 and 215 pm, respectively, irrespective of the conformation of the sugar moiety in the molecules. The Ni ... C, Mn ... C, Ni ... C,O,S and Mn ... C,O,S distances determined in the second and third shells, are in the r ange characteristic for chelated compounds (similar to 287 and similar to 3 90 pm, respectively). The Zn(II) complexes have a four-coordinated square p lanar or tetrahedral structure. The mean Zn-O,N, Zn ... C and Zn ... C,O,S distances are 205, 290 and 390 pm respectively. The Ag(I) complexes are two -coordinated linear polymers with mean Ag-N, Ag-S and Ag ... C distances of 202, 230 and 294 pm. The most likely structures of the complexes are propo sed.