Search results for "solution"
showing 10 items of 5638 documents
Electrochemistry nanometric patterning of MOF particles: Anisotropic metal electrodeposition in Cu/MOF
2006
Abstract Electrodeposition of copper from Cu/MOF immersed into acetate buffer produces a quasi-periodic series of 10–20 nm sized laminae sandwiched within the pristine MOF lattice as monitored by voltammetry of microparticles/atomic force microscopy. This anisotropic patterning can be qualitatively described in terms of a highly orientation-dependent diffusion of electrons and charge-balancing electrolyte counterions in the MOF network.
Structural, magnetic and calorimetric studies of a crystalline phase of the spin crossover compound [Fe(tzpy)2(NCSe)2]
2013
The compound [Fe(tzpy)2(NCSe)2] (tzpy = 3-(2-pyridyl)-[1,2,3]triazolo[1,5-a]pyridine)) has been synthesized and its crystal structure, magnetic behavior and calorimetric properties investigated. Samples constituted of single crystals of [Fe(tzpy)2(NCSe) 2] display a relatively cooperative spin-state change centered at T1/2 ¿ 251.7 K with a hysteresis loop 3.5 K wide. The average enthalpy (¿H) and entropy (¿S) changes upon the spin crossover behavior (SCO) obtained from DSC measurements are 11.1 ± 0.4 kJ mol -1 and 44.5 ± 3 J K-1 mol-1, respectively. The magnetic and calorimetric data have been satisfactorily simulated using the mean-field regular solution model (Slichter-Drickamer) and the …
Designing Solid Solutions of Enantiomers: Lack of Enantioselectivity of Chiral Naphthalimide Derivatives in the Solid State
2017
The enantiomers of a previously reported naphthalimide derivative are shown in this study to form a solid solution; furthermore, on the basis of the knowledge of solid solution structural aspects other naphthalimide derivatives have been synthesized and shown to lack the enantioselectivity in the solid state. The structural origin of solid solution formation is the same as observed in most of the cases in the literaturequasi-centrosymmetric structures form at nonracemic compositions where the most abundant enantiomer adjusts its conformation to mimic the absent one. Such solid solutions belong to the type showing some enantioselectivity. An extended single crystal X-ray diffraction study o…
Rate-limiting reaction of C 3 S hydration - A reply to the discussion “A new view on the kinetics of tricalcium silicate hydration” by E. Gartner
2018
Abstract In the case of coupled solids-solution reactions, any mean accelerating or decelerating one of the reaction, will also change the other reaction(s) in the same way, through the coupling mediated by the solution. The observation of any kinetic change by one of these means should not lead to too rapid conclusion on the limitation of kinetics and it must be done with great caution. Contrary to what Gartner mentioned, the acceleration of C3S hydration by the addition of calcium silicate hydrate seeds, is not a trivial evidence suggesting that hydration kinetics “has to be” limited by the C-S-H precipitation and that the C3S dissolution can be neglected. In our paper, efforts have been …
Host molecules containing electroactive cavities obtained by the molecular assembly of redox-active ligands and metal ions
1995
Self-assembly processes of nickel ions with the redox-active ligand 1,4,8,11-tetra(ferrocenylmethyl)-1,4,8,11-tetraazacyclotetradecane (Fc4cyclam) induces the formation of a redox-active cavity of potential use in electrocatalysis.
Postsynthetic Improvement of the Physical Properties in a Metal-Organic Framework through a Single Crystal to Single Crystal Transmetallation
2015
As ingle crystal to single crystal transmetallation process takes place in the three-dimensional (3D) metal- organic framework (MOF) of formula Mg II 2{Mg II 4(Cu II 2- (Me3mpba)2)3}·45 H2 O( 1 ;M e 3mpba 4¢ = N,N'-2,4,6-trimethyl- 1,3-phenylenebis(oxamate)). After complete replacement of the Mg II ions within the coordination network and those hosted in the channels by either Co II or Ni II ions, 1 is transmetallated to yield two novel MOFs of formulae Co2 II {Co II 4(Cu II 2(Me3- mpba)2)3}·56 H2 O( 2 )a nd Ni2 II {Ni II 4(Cu II 2(Me3mpba)2)3}· 54 H2 O( 3). This unique postsynthetic metal substitution affords materials with higher structural stability leading to enhanced gas sorption and m…
Determination of the stoichiometry of mixed microcrystals K x Cs y ZnCl 4 using instrumental neutron activation analysis
1998
Instrumental neutron activation analysis (INAA) has been employed as an absolute method for the determination of the stoichiometry of mixed microcrystals KxCsyZnCl4 with a weight ranging between 20 and 50 μg. The reliability of the method has been checked with the pure substances KCl, NaCl, CsCl and RbCl, for which the mean value of the ratio Cl/X was found to be 1.04 (3).
Über die Inhibitoren der Korrosion IV(1). Versuche zur Unterdrückung der Auflösung von Aluminium durch organische Substanzen in saurer und alkalische…
1965
Oniumsalze oder potentielle Oniumsalze sind wirksame Inhibitoren der Auflosung von Aluminium in Salzsaure. Ihr Schutz ist im alkalischen Medium geringer. Corrosion Inhibitors IV. Investigations into the suppression of the dissolution of aluminium by organic substances in acid and alkaline solution Onium salts or potential onium salts are effective inhibitors in respect of the dissolution of aluminium in hydrochloric acid. In the alkaline medium, the protective effect is less marked.
Electrochemical Detection of High Oxidation States of Chromium( IV and V ) in Chromium‐Doped Cassiterite and Tin‐Sphene Ceramic Pigmenting Systems
2006
Solid-state electrochemistry is applied to detect the presence of chromium centres with high oxidation states in chromium-doped cassiterite and tin-sphene ceramic pigmenting systems. Voltammetric data indicate that CrV and CrIV centres with different coordinative arrangements exist in the studied materials, and yield proton-assisted reduction processes at +0.95, +0.42 AgCl/Ag in contact with 0.50 M H2SO4. Electrochemical measurements are correlated with spectroscopic data. The CrIV and CrV metal ions display a significant light-driven electrocatalytic effect on the oxidation of 1,4-dihydrobenzoquinone and Fe(CN)64– ions that involves the formation of surface-confined adducts. (© Wiley-VCH V…
Selective CO2 adsorption by a triazacyclononane-bridged microporous metal-organic framework.
2011
Metal-organic frameworks constructed by self-assembly of metal ions and organic linkers have recently been of great interest in the preparation of porous hybrid materials with a wide variety of functions. Despite much research in this area and the large choice of building blocks used to fine-tune pore size and structure, it remains a challenge to synthesise frameworks composed of polyamines to tailor the porosity and adsorption properties for CO(2). Herein, we describe a rigid and microporous three-dimensional metal-organic framework with the formula [Zn(2)(L)(H(2)O)]Cl (L=1,4,7-tris(4-carboxybenzyl)-1,4,7-triazacyclononane) synthesised in a one-pot solvothermal reaction between zinc ions a…