Complexes of thallium (I) ion with adenine and adenosine at different temperatures and constant ionic strength

摘要

The protonation equilibria of Adenine, Adenosine and their complex formation with thallium(]) ion in aqueous solution were studied using a combination of potentiometric and spectrophotometric methods at different temperatures (10, 15, 20, 25, 30 and 35) °C and constant ionic strength (0.1 mol dm? sodium perchlorate). An accurate and sophisticated method based on chemometrical concepts was applied in order to determine stability constants. For this purpose, spectral titration data were used and the spectra were recorded in the range (200-500 nm). The stability constants of thallium (I) ion with all the heterocyclic bases were calculated at various temperatures by means of computer fitting of the pH-absorbance data with appropriate mass balance equations according to mono- and di- acids. The computer program equispec was used to extract the desired information from the spectral data. The outputs of the fitting processes were protonation and stability constants, spectral profiles of pure forms, distribution diagrams, and other factor analysis data. The composition of the formed complexes was determined and it was shown that thallium(1) forms two mononuclear 1:1 species with the ligands, of the type TI(HL) and TIL in the pH range of study (1.0 — 12.4), where L represents each heterocyclic base. Finally, The effect of temperature on the protonation and stability constants were studied and thermodynamic functions have been obtained for the complexes of thallium(L) ion with the heterocyclic bases from the stability constants values and their temperature dependence.