ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Stereochemistry of New Nitrogen-Containing Heterocyclic Compounds. XIV. Potentiometric and Thermodynamic Studies of 5-(Phenylazo)-8-hydroxyquinolines and their Metal Complexes

A. M. Khedr, A. A. El-Bindary, and A. M. Abd El-Gawad

Department of Chemistry, Faculty of Science, Tanta University, Tanta, Egypt

E-mail: abindary@yahoo.com

Received: 6 September 2004

Abstract: A series of 5-(phenylazo)-8-hydroxyquinolines (HL1—HL6) have been prepared and characterized by elemental analysis and IR spectra. Proton-ligand dissociation constants of 5-(phenylazo)-8- hydroxyquinoline derivatives and metal—ligand stability constants of their complexes with metal ions (La³⁺, Ce³⁺, Pr³⁺, Zr⁴⁺, Hf⁴⁺, and Th⁴⁺) have been determined potentiometrically in 0.1 M-KCl and 40 vol. % CH₃OH—water mixture. The influence of substituents on the dissociation and stability constants was examined on the basis of the electron-repelling property of the substituent. The stability constants of the formed complexes increase in the order La³⁺, Ce³⁺, Pr³⁺, Zr⁴⁺, Hf⁴⁺, Th⁴⁺. The effect of temperature was studied and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were derived and discussed.

Full paper in Portable Document Format: 595a336.pdf

Chemical Papers 59 (5) 336–342 (2005)