Search results for "Chemical stability"
showing 10 items of 96 documents
Two Novel Polyoxometalate-Encapsulated Metal–Organic Nanotube Frameworks as Stable and Highly Efficient Electrocatalysts for Hydrogen Evolution React…
2018
Two novel polyoxometalate (POM)-encapsulated metal–organic nanotube (MONT) framework crystalline materials with unprecedented copper-mixed ligands, HUST-200 and HUST-201, have been successfully synthesized by an effective synthesis strategy. The encapsulation not only provides a shield to increase the chemical stability, but also does not affect its catalytic activity, and, therefore, the crystalline materials are very active for HER (H+ can diffuse easily through the pores of the MONTs). Remarkably, HUST-200 displays a low overpotential of 131 mV (catalytic current density is equal to 10 mA·cm–2). This work thus offers a new way for devising HER electrocatalysts with low cost using POM-enc…
Oxidative decarboxylation of naproxen.
1992
The decarboxylation of naproxen (1H) and its salt (1-) was achieved by means of chemical [Ce(IV) or S2O8(2-)] and electrochemical oxidation. The product patterns were compatible with mechanisms involving single-electron transfer from the pi-system or the carboxylate moiety. The results are discussed in connection with the involvement of electron-transfer processes in the reported phototoxicity of naproxen.
Photoelectrical properties of thin films of DMABI derivatives
2011
Organic thin films with semiconducting properties have been intensively studied in nowadays due to very promising applications in organic electronics, for example, organic photovoltaic. Among organic semiconductors, group of indandiones with their photoelectrical properties, thermal and chemical stability are good candidates for use in design of novel molecular electronic devices. We have investigated photoconductivity quantum efficiency and its spectral dependence of two dimetilaminobenzylidene-1,3-indandione derivatives. Values of the photoconductivity threshold energy and optical energy gap are obtained. These results are compared with calculated transfer energy gap estimated according t…
A solution study of complex formation between iron(III) and oxalate in dimethylsulphoxide
1991
The complex formation between iron(III) and oxalic acid (ethanedioic acid, H2ox) has been studied by potentiometry in dimethylsulphoxide (dmso) solution. H2ox behaves as a weak diprotic acid in such a solvent, with overall association constants: log βj1=8.551(3) and log βj2=14.242(3) at 25°C and 0.1 Mn-Bu4NClO4. A reliable set of overall stability constants for the iron(III)-oxalato complexes, log β11=13.16(4), log β12=23.66(4) and log β13=30.75(4), have been obtained for the first time under identical conditions. The electrochemical behaviour of such complexes was studied in dmso at a platinum electrode. The coordination ability of oxalate towards iron(III) in dmso and water media is compa…
Ab initio study of phase competition in (La1−c,Src)CoO3 solid solutions
2013
Abstract (La 1 − c ,Sr c )CoO 3 (LSC) solid solutions are promising materials for high temperature electrochemical cells and cathodes of solid oxide fuel cells. The Density Functional Theory (DFT) was applied to calculate the energies of the different superstructures in LSC which are stable with respect to formation of anti-phase domains. The energy parameters determining the relative stability of the cubic superstructures (phases) are extracted from these calculations. Using the Concentration Wave formalism and the energy parameters for different phases from DFT calculations, the temperature dependences of the long-range order parameters were obtained characterizing the order–disorder tran…
Highly stable and porous porphyrin-based zirconium and hafnium phosphonates – electron crystallography as an important tool for structure elucidation
2018
The Ni-metallated porphyrin-based tetraphosphonic acid (Ni-tetra(4-phosphonophenyl)porphyrin, Ni-H8TPPP) was used for the synthesis of highly porous metal phosphonates containing the tetravalent cations Zr4+ and Hf4+. The compounds were thoroughly characterized regarding their sorption properties towards N2 and H2O as well as thermal and chemical stability. During the synthesis optimization the reaction time could be substantially decreased under stirring from 24 to 3 h in glass vials. M-CAU-30, [M2(Ni-H2TPPP)(OH/F)2]·H2O (M = Zr, Hf) shows exceptionally high specific surface areas for metal phosphonates of aBET = 1070 and 1030 m2 g-1 for Zr- and Hf-CAU-30, respectively, which are very clos…
A phosphonamidate containing aromatic N-terminal amino group as inhibitor of leucine aminopeptidase-design, synthesis and stability.
2006
Fully deprotected phosphonamidate dipeptides, predicted as effective inhibitors of cytosolic leucine aminopeptidase, showed unexpected instability in water solution at pH below 12. Their hydrolysis rate was strictly correlated with basicity of the N-terminal amino group. To improve this feature a phosphonamidate analogue containing less basic, aromatic 2-aminophenylphosphonate residue in P1 position of the inhibitor was designed. The target compound was synthesised starting from diethyl 2-nitrophosphonate in several step procedure. The decrease in basicity of the terminal amino moiety of the modified analogue in fact resulted in satisfactory improvement of hydrolytic stability of the P–N bo…
Physicochemical stability of human insulin 1 I.U./mL infusion solution in 50 mL polypropylene syringes
2021
Abstract Objectives The objective of this study was to investigate the physicochemical stability of human insulin 1 I.U./mL injection solutions (Insuman® Rapid) diluted with 0.9% NaCl solution in 50 mL disposable three-piece polypropylene syringes and stored refrigerated or at room temperature. Methods 1 I.U./mL test solutions were prepared with Insuman® Rapid and 0.9% sodium chloride infusion solution in 50 mL Original-Perfusor® syringes and BD® Perfusion syringes. Test solutions were stored for 90 days at 2–8 °C/dark or 48 h at 20–25 °C/diffuse room light in order to determine chemical stability. Additional test solutions were stored 28 days at 2–8 °C/dark followed by 24 h at 20–25 °C/dif…
European Databases on Stability and Compatibility of Injectable Medicinal Products in Europe
2020
AbstractIn hospitals, the majority of medication therapy is administered intravenously. Especially, in intensive care units, simultaneous of various injectable drugs is a common practice Drug incompatibilities have been reported to be associated with up to 60 % of all serious and life-threatening adverse drug events. Several databases are used by hospital pharmacists to answer the questions of (in)compatibility of co-administered injectable drugs. The objective of this article is to present the European databases on compatibility and stability of injectable drugs. According to a questionnaire which was sent to the National Hospital Pharmacy Associations of the 28 countries of European Commu…
Polymorphs and Hydrates of Sequifenadine Hydrochloride: Crystallographic Explanation of Observed Phase Transitions and Thermodynamic Stability
2017
In this study, detailed analysis of crystal structures was used to rationalize the observed stability and phase transformations of sequifenadine hydrochloride polymorphs and hydrates, as well as to understand the observed structural diversity. The performed polymorph and hydrate screening revealed the existence of six polymorphs and four hydrates. Crystal structures of these phases were determined either from single crystal or from powder diffraction data. The different possibilities for packing of sequifenadine cations were found to be the main reason for the observed structural diversity of polymorphs. The hydrate structures were found to be structurally similar and related to those of pa…