Adenosine bear ing 18-crown-6 and 15-crown-5 ether moiety was synthesized. Comparison of complexing ability to wards alkali metal ions revealed strong potassium and sodium preference. Complex formation constants were estimated and thermodynamic parameters calculated.
The mode of coordination of the complexes formed in the systems Cu/spermine/nucleoside (or nucleotide) was proposed on the basis of the equilibrium and spectral studies. Significant differences were found in the coordination character of nucleosides and nucleotides. In the systems with adenosine or cytidine, mixed-ligand complexes are formed with the N5 type coordination. On the other hand, in the systems with their monophosphates, molecular complexes are formed with metal ions coordinated through monophosphates, molecular complexes are formed with metal ions coordinated through oxygen atoms from the phosphate groups. Spermine, left outside the inner coordination sphere, is involved in non-covalent interactions with nitrogen atoms from the nucleotide bases.
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