Coordination Sphere Of Copper Ion Research Articles

Insights into the coordination sphere of copper ion in polymers containing carboxylic acid and azole groups

In this work, we describe the Cu2+ ion uptake from recently developed hydrogel with polyampholyte and polyelectrolyte behavior at different concentrations of the metal ion. Solid-state NMR and EPR were used as complementary techniques to understand the coordination role of carboxylic acid and azole groups (imidazole, triazole and pyrazole) involved in the copper ion coordination. In polymers containing imidazole and triazole, the uptake took place preferentially through the azole groups, with less participation of the carboxylate groups at low concentrations of Cu2+. However, as the concentration of Cu2+ increased, these azole ligands became less active in the new sites for copper. In polymers containing pyrazole, coordination of Cu2+ was through both carboxylate and pyrazole ligands, regardless of the concentration of Cu2+.Interactions of the different ligands in the networks and the structural changes produced by copper ions (Cu1+, Cu2+) were characterized by thermal and NMR measurements.

Copper-Mediated Oxidative Cyclization of Heterocyclically Substituted Aldimines

Copper-mediated cascade reactions were performed with heterocyclically substituted aldimines. These oxidative heterocyclizations include sequences of oxidations and cycloadditions or nucleophilic additions which take place in the coordination sphere of copper ions. When two heterocyclically substituted aldimines were reacted in the presence of copper (II) salts under air, pyridine derivatives were produced. In one case a 1,4-diazatricyclo-[3.2.1.02.7]oct-3-ene was also formed. The basic structure of this new tetracyclic compound contains five new chirale carbon atoms. This cage-like structure has been revealed by X-ray crystallography. The synthesis of 2H-pyrroles by copper-assisted conversions of the aldimines with dimethylacetylene carboxylate or quinones was also described.

The effect of copper ions on adsorption of histamine and histidine on the surface of highly dispersed silica

The effect of copper ions on the adsorption of histamine and histidine on the surface of highly dispersed silica from aqueous solutions is studied. It is shown that the formation of complex particles in solution determines the character of adsorption of these biomolecules. The equilibrium constants of the formation of ternary surface complexes, where silanol groups of silica act as a ligand, are calculated. It is shown that, in such complexes, nitrogen atoms of either histamine or histidine enter into the inner coordination sphere of copper ion.

Interaction centres of pyrimidine nucleotides: Cytidine-5′-diphosphate (CDP) and cytidine-5′-triphosphate (CTP) in their reactions with tetramines and Cu(II) ions

The interactions between pyrimidine nucleotides: cytidine-5′-diphosphate (CDP) and cytidine-5′-triphosphate (CTP) and Cu(II) ions, spermine (Spm) and 1,11-diamino-4,8-diazaundecane (3,3,3-tet) have been studied. The composition and stability constants of the complexes formed have been determined by means of the potentiometric method, while the centres of interactions in the ligands have been identified by the spectral methods (UV–Vis, Ultraviolet and Visible spectroscopy; EPR, electron spin resonance; NMR). In the systems without metal, formation of the molecular complexes nucleotide–polyamine with the interaction centres at the endocyclic nitrogen atom of purine ring N(3), the oxygen atoms of the phosphate group from the nucleotide and protonated nitrogen atoms of the polyamine have been detected. Significant differences have been found in the metallation between the systems with Spm and with 3,3,3-tet. In the systems with spermine, mainly protonated species are formed with the phosphate group of the nucleotide and deprotonated nitrogen atoms of the polyamine making the coordination centres, while the donor nitrogen atom of the nucleotide N(3) is involved in the intramolecular interligand interactions, additionally stabilising the complex. In the systems with 3,3,3-tet, the MLL′ type species are formed in which the oxygen atoms of the phosphate group and nitrogen atoms of the polyamine are involved in metallation, whereas the N(3) atom from the pyrimidine ring of the nucleotide is located outside the inner coordination sphere of copper ion. The main centre of Cu(II) interaction in the nucleotide, both in the system with Spm and 3,3,3-tet is the phosphate group of the nucleotide.