Solution Equilibria of Cobalt(II)- and Nickel(II)- 2,2',2"-Terpyridine-Amino Acids Ternary Systems

Chcmistry Department, Faculty of Science, Minia University, Minia, Egypt Chemistry Department, Faculty of Science, Assiut University, Assiut. Egypt Manuscript received 30 July 1993, accepted 12 October 1993 Solution equilibria of the ternary systems CoII., Ni II-2,2',2"-terpyridine-mono- or dicarboxylic amino adds are investigated potentiometrically. The stability constants of the binary and ternary complexes are determined at 20° and ionic strength of 0.2 mol dm-3 (NaCIO4). It is duduced that the stability of the ternary complex containing the secondary ligand monocarboxylic amino acid is lower than that of the corresponding binary amino acid-metal complex. On the other hand, a reverse behaviour is observed for the secondary ligand dicarboxylic amino acid. Stability of different complexes is examined and discussed in terms of the molecular structure of the amino acid moiety