Complexes of pyrimidine DNA bases with thallium(I)

The stability constants of complexes of a thallium(I) ion with cytosine and thymine were determined in aqueous solution at 25°C and 0.1 mol dm⁻³ ionic media, using a combination of potentiometric and spectrophotometric techniques. Sodium perchlorate was used to maintain the ionic strength. The composition of the formed complexes was determined and it was shown that thallium(I) forms two mononuclear 1:1 species with cytosine of the type TIHL⁺ and TIL, and a mononuclear 1:1 complex species with thymine in the form TIHL, in the pH range of study (1–11), where L represents the fully dissociated ligand. The cumulative stability constants, β _xyz, of the complexes, (thallium)_x(H)_y(ligand)_z], were calculated by a nonlinear fitting method and their distributions were presented as a function of-logH⁺]. This text was submitted by the authors in English.