Potentiometric and Thermodynamic Studies of Some Metal–Cysteine Complexes

Potentiometric and Thermodynamic Studies of Some Metal–Cysteine Complexes A new and simple potentiometric method is developed to determine the stability constants of cysteine complexes with Mn(II), Cu(II), Zn(II), Cd(II), and Ce(III) metal ions using a modified Bjerrum method. Potentiometric titrations were performed in water and water/dioxane mixtures at five different temperatures. The least and highest stable complexes were those of Cu(II) and Zn(II), respectively. Furthermore, by conducting the experiments at temperatures of 15, 20, 25, 35, and 45 °C, the thermodynamic parameters ΔH°, ΔS°, and ΔG° for the pertinent complexes were calculated. The results show that the ΔH° values of the complexes are positive except for Zn(II). Negative values of ΔG° are evidence for the spontaneity of the reactions. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of the Chinese Chemical Society Wiley

Potentiometric and Thermodynamic Studies of Some Metal–Cysteine Complexes

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Publisher
Wiley
Copyright
© 2018 The Chemical Society Located in Taipei & Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim
ISSN
0009-4536
eISSN
2192-6549
D.O.I.
10.1002/jccs.201700022
Publisher site
See Article on Publisher Site

Abstract

A new and simple potentiometric method is developed to determine the stability constants of cysteine complexes with Mn(II), Cu(II), Zn(II), Cd(II), and Ce(III) metal ions using a modified Bjerrum method. Potentiometric titrations were performed in water and water/dioxane mixtures at five different temperatures. The least and highest stable complexes were those of Cu(II) and Zn(II), respectively. Furthermore, by conducting the experiments at temperatures of 15, 20, 25, 35, and 45 °C, the thermodynamic parameters ΔH°, ΔS°, and ΔG° for the pertinent complexes were calculated. The results show that the ΔH° values of the complexes are positive except for Zn(II). Negative values of ΔG° are evidence for the spontaneity of the reactions.

Journal

Journal of the Chinese Chemical SocietyWiley

Published: Jan 1, 2018

Keywords: ; ; ;

References

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