Complexation of aluminium(III) with several bi- and tri-dentate amino acids

Complex formation between AlIII and various bidentate and potentially tridentate amino acids (Gly, Ser, Thr, Gln, Asn, Glu and Asp) and some model compounds (N-acetylaspartic acid, succinic acid, and 2-sulfanylsuccinic acid) was studied in aqueous solution by pH-potentiometric and multinuclear (1H, 13C and 27Al) NMR techniques. A weak interaction through the carboxylate function was unambiguously detected for all of these ligands. For Asp, however, which contains two carboxylates and a central amino donor, tridentate co-ordination is strongly suggested. Although its steric environment is similar to that of the amino function in Asp, binding of the thiolate sulfur of 2-sulfanylsuccinic acid could not be verified.