POTENTIOMETRIC STUDIES OF BINARY AND TERNARY COMPLEXES OF ZN(II) WITHTRIETHYLENETETRAMINE AS PRIMARY LIGAND AND SELECTED AMINO-ACIDS AND DNA UNITS AS SECONDARY LIGANDS
Mm. Shoukry et al., POTENTIOMETRIC STUDIES OF BINARY AND TERNARY COMPLEXES OF ZN(II) WITHTRIETHYLENETETRAMINE AS PRIMARY LIGAND AND SELECTED AMINO-ACIDS AND DNA UNITS AS SECONDARY LIGANDS, Mikrochimica acta, 127(1-2), 1997, pp. 105-111
The acid-base equilibria of triethylenetetramine (Trien) and the forma
tion equilibria of binary and ternary complexes of Zn(II) with Trien a
s primary ligand and some selected amino acids and DNA units as second
ary ligands have been investigated. The results showed the formation o
f a 1:1 Zn(Trien)(2+) complex. At higher pH, the Zn(Trien)(2+) complex
is hydrolysed to give Zn(Trien) (OH)(+) and Zn(Trien)(OH)(2) complexe
s. The fraction of the mono-hydroxo species attains a maximum of 81.3%
at pH 10. The stability constants K(Zn(Trien)A)(Zn(Trien)) for the te
rnary complexes were determined. Histidine coordinates in a histamine-
like way. Lysine and ornithine ligate by the two amino groups. Serine
and methionine are bound in a glycine-like mode. However, penicillamin
e, cysteine and glutathione ligate partly like mercaptoethylamine and
partly like mercaptopropionic acid. In the case of DNA complexes, inos
ine is bound through the N-1 atom. However, uracil, uridine, thymine a
nd thymidine ligate through the N-1 atom. The relative stabilities of
ternary complexes are compared with those of the corresponding binary
complexes in term of Delta log K values. The concentration distributio
n diagrams of the complexes are evaluated.