Stability and mode of coordination complexes formed in the silver(i)/nucleoside systems

Complexes of silver(i) with nucleosides (adenosine, cytidine, uridine and thymidine) have been studied using potentiometric, spectral and theoretical methods. Stability constants of the complexes as well as their coordination modes have been determined. Results of the equilibrium studies have provided evidence for the formation of only ML and ML(OH) type complexes. The basicity of nucleosides was found to substantially influence the stability constant of the ML type complexes. Spectral data have allowed us to identify the sites of silver attachment to the nucleoside. Additionally a new silver-adenosine complex of stoichiometry Ag(Ado)(OH) was prepared from aqueous solution at pH close to 6. Its characterization and comparison with complexes formed in solution are described. The structures of complexes formed in solution and in solid state were confirmed through computational calculations (DFT/B3LYP: lanL2DZ theoretical procedure). © 2011 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique

Coordination Reactions and Noncovalent Interactions of Polyamines with Nucleotides in Binary Systems and with Nucleotides and Copper(II) Ion in Ternary Systems

Interactions of nucleotides (AMP, CMP) and 1,2-diaminopropane (tn-1) or 2-methyl-1,2-diaminopropane (tn-2) in metal-free systems as well as in the systems including copper(II) ions were studied. The composition and overall stability constants of the complexes formed were determined by the potentiometric method, whereas the interaction centres and coordination sites were identified by spectroscopic methods. It was found that phosphate groups of nucleotides and the protonated amine groups of polyamines are the centres of interaction. The differences in the interactions with the polyamines which act as models of biogenic amines are impacted by the presence of lateral chains (methylene groups) in tn-1 and tn-2. In the ternary systems with Cu(II) ions, the heteroligand complexes are mainly of the ML⋯L’ type, in which the protonated polyamine is engaged in noncovalent interactions with the anchoring Cu(II)-nucleotide complex. The complexes formed in the Cu/NMP)/tn-1 system are more stable than those formed in the system with tn-2. The mode of coordination in the complex is realised mainly through the phosphate groups of the nucleotide with involvement of the endocyclic nitrogen atoms in a manner which depends upon the steric conditions and in particular on the number of the methylene groups in the polyamine molecule