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

Polymer Engineering

Polymer Engineering focuses on the preparation and application of polymers in several hot topics such as artificial photosynthesis, water purification by membrane technologies, and biodiesel production from wastewater plants. The authors not only describe the latest developments in polymer science, but also support these experimental results by computational chemistry and modelling studies

Coordination Chemistry of Phosphate Groups in Systems Including Copper(II) Ions, Phosphoethanolamine and Pyrimidine Nucleotides

The activity of phosphate groups of phosphoethanolamine and pyrimidine nucleotides (thymidine 5-monophosphate, cytidine 5-monophosphate and uridine 5’monophosphate) in the process of complexation metal ions in aqueous solution was studied. Using the potentiometric method with computer calculation of the data and spectroscopic methods such as UV-Vis, EPR, 13C and 31P NMR as well as FT-IR, the overall stability constants of the complexes as well as coordination modes were obtained. At lower pH, copper(II) ions are complexed only by phosphate groups, whereas the endocyclic nitrogen atom of nucleotides has been identified as a negative center interacting with the -NH3+ groups of phosphoethanolamine

The Effect of pH on the Size of Silver Nanoparticles Obtained in the Reduction Reaction with Citric and Malic Acids

In colloidal methods, the morphology of nanoparticles (size and shape) as well as their stability can be controlled by changing the concentration of the substrate, stabilizer, adding inorganic salts, changing the reducer/substrate molar ratio, and changing the pH and reaction time. The synthesis of silver nanoparticles was carried out according to the modified Lee and Meisel method in a wide pH range (from 2.0 to 11.0) using citric acid and malic acid, without adding any additives or stabilizers. Keeping the same reaction conditions as the concentration of acid and silver ions, temperature, and heating time, it was possible to determine the relationship between the reaction pH, the type of acid, and the size of the silver nanoparticles formed. Obtained colloids were analyzed by UV-Vis spectroscopy and investigated by means of Transmission Electron Microscope (TEM). The study showed that the colloids reduced with citric acid and malic acid are stable over time for a minimum of seven weeks. We observed that reactions occurred for citric acid from pH 6.0 to 11.0 and for malic acid from pH 7.0 to 11.0. The average size of the quasi-spherical nanoparticles changed with pH due to the increase of reaction rate

PVDF Membrane Morphology—Influence of Polymer Molecular Weight and Preparation Temperature

In this study, we successfully prepared nine non-woven, supported polyvinylidene fluoride (PVDF) membranes, using a phase inversion precipitation method, starting from a 15 wt % PVDF solution in N-methyl-2-pyrrolidone. Various membrane morphologies were obtained by using (1) PVDF polymers, with diverse molecular weights ranging from 300 to 700 kDa, and (2) different temperature coagulation baths (20, 40, and 60 ± 2 °C) used for the film precipitation. An environmental scanning electron microscope (ESEM) was used for surface and cross-section morphology characterization. An atomic force microscope (AFM) was employed to investigate surface roughness, while a contact angle (CA) instrument was used for membrane hydrophobicity studies. Fourier transform infrared spectroscopy (FTIR) results show that the fabricated membranes are formed by a mixture of TGTG’ chains, in α phase crystalline domains, and all-TTTT trans planar zigzag chains characteristic to β phase. Moreover, generated results indicate that the phases’ content and membrane morphologies depend on the polymer molecular weight and conditions used for the membranes’ preparation. The diversity of fabricated membranes could be applied by the End User Industries for different applications

The Influence of pH on Complexation Process of Copper(II) Phosphoethanolamine to Pyrimidine Nucleosides

The influence of pH on the complex formation of phosphoethanolamine and pyrimidine nucleosides (uridine, cytidine and thymidine) with copper(II) ions was studied. All investigations were performed in aqueous solution. The overall stability constants of the complexes and non-covalent compounds were obtained using the potentiometric method with computer calculation of the data. Moreover, equilibrium constants of the reaction were determined. The mode of coordination was obtained using spectroscopic methods. Analysis of the potentiometric and spectroscopic data confirmed the involvement and effectiveness of phosphate groups in species formation as well as the influence of pH on the mode of coordination of the investigated biomaterials. In the next step, studied complexes will be applied as potential biomaterials with biological applications