Determination of protonation and stability constants of some triazolethione and oxadiazolethione derivatives by potentiometric and spectrophotometric methods

ABSTRACTMaster ThesisDETERMINATION of PROTONATION and STABILITY CONSTANTS of SOMETRIAZOLETHIONE and OXADIAZOLETHIONE DERIVATIVES byPOTENTIOMETRIC and SPECTROPHOTOMETRIC METHODSNurettin Aykut KÖKSALFirat UniversityGraduate School of Natural and Applied ScienciesDepartment of Chemistry2006, Page: 68In the first stage of this work which was planned in two stages four ligands weresynthesized and characterized. The characterization of the ligands have been achievedthrough spectral techniques such as IR, 1H NMR and 13C NMR. In the second stage,protonation constants of the synthesized ligands and stability constants of their Cu(II),Ni(II), Co(II) metal complexes were determined by potentiometric andspectrophotometric methods in %70 dimethylsulfoxide-%30 water media at 25 ± 0.1oCunder nitrogen atmosphere and at ionic strength of 0.1 M sodium perchlorate. The dataobtained from the potentiometric titrations were evaluated by the computer programBEST developed by Martell Motekaitis, whereas the data from the spectrophotometrictitrations were appraised by a computer program specified in Appendix 1 and Appendix2. Thereafter, using potentiometric titrations values, the distribution diagrams which areindicating the changes of concentrations of the emerging species were plotted as afunction of pH by using computer program SPE, which also developed by Martell-Motekaitis.As a result of the potentiometric and spectrophotometric studies, thestoichiometry of metal(II) complexes of the ligands was found to be 1:1 (ML). It hasbeen observed that all of the ligands examined have two protonation constants. Thestabilities of the complexes produced by the ligands and metal(II) ions have beendetermined to be in conformance with Irwing-Williams series. On the other hand, theend results obtained by comparing values of protonation and stability constants acquiredfrom spectrophotometric and potentiometric methodologies were evaluated.Key Words: Triazolethione, Oksadiazolethione, Spectrophotometric titrations,Potentiometric titrations, Protonation constants, Stability constants