Stability constants of copper(I) and silver(I) complexes with open-chain, macrocyclic and -bicyclic aza-ligands in acetonitrile and comparison with results in dimethylsulfoxide

Entropy and Enthalpy Effects on Metal Complex Formation in Non-Aqueous Solvents: The Case of Silver(I) and Monoamines

Access to the enthalpy and entropy of the formation of metal complexes in solution is essential for understanding the factors determining their thermodynamic stability and speciation. As a case study, in this report we systematically examine the complexation of silver(I) in acetonitrile (AN) with the following monoamines: n-propylamine (n-pr), n-butylamine (n-but), hexylamine (hexyl), diethylamine (di-et), dipropylamine (di-pr), dibutylamine (di-but), triethylamine (tri-et) and tripropylamine (tri-pr). The study shows that the complex stabilities are quite independent of the length of the substitution chain on the N atom and demonstrates that, in general, the overall enthalpy terms associated with the complex formation are strongly exothermic, whereas the entropy values oppose the complex formations. In addition, we examined the similarity of the formation constants of AgL complexes of the primary monoamines in AN, dimethylsulfoxide (DMSO) and water, which were unexpected on the basis of the difference between the donor properties of solvents.

Active silver nanoparticles for wound healing

In this preliminary study, the silver nanoparticle (Ag NP)-based dressing, Acticoat™ Flex 3, has been applied to a 3D fibroblast cell culture in vitro and to a real partial thickness burn patient. The in vitro results show that Ag NPs greatly reduce mitochondrial activity, while cellular staining techniques show that nuclear integrity is maintained, with no signs of cell death. For the first time, transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS) analyses were carried out on skin biopsies taken from a single patient during treatment. The results show that Ag NPs are released as aggregates and are localized in the cytoplasm of fibroblasts. No signs of cell death were observed, and the nanoparticles had different distributions within the cells of the upper and lower dermis. Depth profiles of the Ag concentrations were determined along the skin biopsies. In the healed sample, most of the silver remained in the surface layers, whereas in the unhealed sample, the silver penetrated more deeply. The Ag concentrations in the cell cultures were also determined. Clinical observations and experimental data collected here are consistent with previously published articles and support the safety of Ag NP-based dressing in wound treatment.

Self-assembly of quaterpyridine ligands and Cu+ cation into helical complexes of 2:2 stoichiometry under electrospray ionisation conditions

Solutions containing quaterpyridine ligand 1 and Cu(2+) cation were analysed by electrospray ionisation mass spectrometry (ESI-MS). It was found that copper reduction under ESI conditions and self-assembly of 1 and Cu(I) led to the formation of the 2:2 stoichiometry complex. Such stoichiometry is characteristic of helical complex of quaterpyridine ligand with Cu(I). The isotope pattern characteristic of [Cu(2)1(2)](2+) ion and different from that of [Cu1](+) ion, is observed. When using methanol as solvent, only [Cu(2)1(2)](2+) ions are observed in mass spectrum obtained at low cone voltage. At higher cone voltage [Cu(2)1(2)](2+) ion easy dissociates producing [Cu1](+) ion. When using other solvents studied, water and acetonitrile, 2:2 stoichiometry complex is formed, but along with complexes of other stoichiometries. Helical complex was not observed for silver cation for which only 1:1 stoichiometry complex was observed (ion [Ag1](+)).