Trimethyltin(IV) complexes with some selected DNA constituents

The interaction of the trimethyltin(IV) with some selected DNA constituents such as inosine, inosine 5'-monophosphate, adenine, adenosine, adenosine 5 '-monophosphate, uracil, thymine, thymidine, cytosine and cytidine were inv estigated at 25 degreesC. and 0.1 M ionic strength in aqueous solutions and dioxane-water mixtures using potentiometry. The stepwise formation constan ts of the complexes formed in solution were calculated using the non-linear least-square program MINIQUAD-75. The concentration distribution of the va rious complex species was evaluated as a function of pH. The effect of diox ane as a solvent on the protonation constants of ligands and the formation constants of trimethyltin(TV) complexes were discussed. The thermodynamic p arameters DeltaH degrees and DeltaS degrees calculated from the temperature dependence of the equilibrium constants were investigated.