Ternary complexes in solution. 34. Discriminating and stability increasing properties of the imidazole moiety in mixed-ligand complexes

1980 ◽  
Vol 19 (5) ◽  
pp. 1411-1413 ◽  
Author(s):  
Helmut Sigel
Keyword(s):  
Ternary Complexes ◽  
Mixed Ligand ◽  
Mixed Ligand Complexes

Ternary Complexes in Solution, XII. Models for Biological Mixed-Ligand Complexes: 2,2′-Bipyridyl-Cu2+-Oligoglycine Systems

1972 ◽  
Vol 27 (4) ◽  
pp. 353-364 ◽  
Author(s):  
Helmut Sigel ◽  
Rolf Griesser ◽  
Bernhard Prijs
Keyword(s):  
Coordination Sphere ◽  
Ternary Complexes ◽  
Mixed Ligand ◽  
Amide Group ◽  
Amide Proton ◽  
Mixed Ligand Complexes ◽  
Apical Position ◽  
Binary Complexes ◽  
The Stability ◽  
Ph Range

The stability constants of the binary Cu2+ complexes of glycine amide, diglycine, diglycine amide, triglycine, and tetraglycine were determined, as were those of the mixed-ligand Cu2+ systems containing 2,2′-bipyridyl and one of the mentioned oligoglycines. The results evidence that all these complexes have the same structure and, therefore, the binding sites of the ligands have to be the terminal amino group and the oxygen of the neighbored amide group. The stability differences between the ternary and the binary complexes are in agreement with this interpretation. It is of interest to note that these ternary complexes are significantly more stable than expected on statistical reasons. With increasing pH, the amide groups in the binary complexes are successively deprotonated. Thus, with tetraglycine finally all three amide protons are displaced, and the amide nitrogens are bound to the square-planar coordination sphere of Cu2+. As in the Cu2+-2,2′-bipyridyl 1 : 1 complex, only two coordination positions are left for the binding of the oligoglycine, in the tenary complexes, only one amide group can be deprotonated. An increase in pH with deprotonation of other amide groups leads to a displacement of 2,2′-bipyridyl, i. e. the simple binary complexes result. No evidence could be observed for the coordination of a deprotonated amide group to an apical position of the coordination sphere of Cu2+. Additionally, while the displacement of the first amide proton in the several binary Cu2+ oligoglycine complexes occurs over a large pH range (4 to 7), the deprotonation in all the mixed-ligand complexes takes place at pH approximately 8.

Potentiometric Studies On Mixed Ligand Complexes

1972 ◽  
Vol 27 (3) ◽  
pp. 308-311 ◽  
Author(s):  
R. C. Sharma ◽  
J. P. Tandon
Keyword(s):  
Ternary Complexes ◽  
Mixed Ligand ◽  
Mixed Ligand Complexes ◽  
Potentiometric Studies ◽  
Hydroxy Acids

Potentiometric evidences have been cited for the formation of 1:1:1, ternary complexes in the systems La (III) -NTA-Hydroxy acids (where hydroxy acids = malic, tartaric, 1-hydroxy 2-naphthoic and 2-hydroxy-3 naphthoic acids).

scholarly journals Stability Constants of Mixed Ligand Complexes of Transition Metal(II) Ions withN-(2-Hydroxy-1-naphthylidene)-2,6-diisopropylaniline as Primary Ligand and N-(2-Hydroxybenzylidene)-2,3-dimethylaniline as Secondary Ligand

2011 ◽  
Vol 8 (1) ◽  
pp. 123-126
Author(s):  
A. K. Mapari ◽  
K. V. Mangaonkar
Keyword(s):  
Transition Metal ◽  
Stability Constants ◽  
Ternary Complexes ◽  
Mixed Ligand ◽  
Mixed Ligand Complexes ◽  
Water Medium ◽  
Binary And Ternary Complexes ◽  
Secondary Ligand

Binary and ternary complexes of the type M-Y and M-X-Y [M = Co(II), Ni(II), Cu(II) and Zn(II); X = N-(2-hydroxy-1-naphthylidene)-2,6-diisopropylaniline and Y =N-(2-hydroxybenzylidene)-2,3-dimethylaniline] have been examined pH-metrically at 27±0.5°C and µ = 0.1 M in 75: 25% (v/v) 1,4-dioxne-water medium. The logarithms of the values of stability constants for binary (M-Y) and for ternary (M-X-Y) systems were calculated.

Mixed-ligand complexes involving sulfur-containing ligands. Part 1. Nickel(II) ternary complexes of L-cysteine, D-penicillamine and L-cysteic acid with imidazoles

1993 ◽  
pp. 917 ◽  
Author(s):  
M. Sivasankaran Nair ◽  
P. Thillai Arasu ◽  
M. Sankaranarayana Pillai ◽  
Chidambaram Natarajan
Keyword(s):  
Ternary Complexes ◽  
Mixed Ligand ◽  
Cysteic Acid ◽  
Mixed Ligand Complexes ◽  
Sulfur Containing
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