Synthesis of some schiff bases and their metal complexes, determination of their protonation and stability constant by potentiometric titration method

n ABSTRACT Ph.D. Thesis SYNTHESIS OF SOME SCHIFF BASES and THEIR METAL COMPLEXES, DETERMINATION OF THEIR PROTONATION AND STABILITY CONSTANTS BY POTENTIOMETRIC TITRATION METHOD Ibrahim YILMAZ Fırat University Graduate School of Natural and Applied Sciencies Department of Chemistry 2002, Page: 97 In the first stage of this work which was planned in two stages, fourteen Schiff bases containing cyclobutane and thiazole groups and their Cu(II), Ni(II) ve Zn(II) complexes were synthesised and characterized. In the characterization of the Schiff bases and their complexes, IR, *H NMR spectral techniques and elemental analysis, thermal analysis techniques ( TGA and DSC) and magnetic susceptibility were used. In the second stage, protonation constants of the ligands and stability constants of their Cu(II), Ni(II), Zn(II) complexes were determined by potentiometric titration method in %60 dioxane-%40 water media at 25 ± 0.1°C under nitrogen atmosphere and at ionic strength of 0.1 M sodium perchlorate. Obtained data from the titrations were evaluated by a computer programme, BEST. After that, by using these values, the distribution diagrams which is indicating the changes of concentrations of the species as a function of pH were plotted via the computer programme developped by Martell-Motekaitis. As a result of the spectroscopic and analytical investigations, the stoichiometry of metal complexes of the ligands was found to be 1:2 (ML2). The data obtained from the titrations are supported this observation. It has been observed that all the Schiff base ligands titrated here have three protonation constants. The stabilities of the complexes of the ligands accommodated with Irwing- Williams order. On the other hand, attempts to investigate the effects of the substituents on the protonation constants of the Schiff bases were failed since the substituents are far away from the protonable parts of the molecules, except for phenolic OH. Key Words: Substituted Cyclobutane, Thiazole, Schiff Bases, Thiosemicarbazone, Potentiometric Titrations, Protonation Constants, Stability Constants.