Search results for "Atrane"
showing 10 items of 24 documents
Silica-based powders and monoliths with bimodal pore systemsElectronic supplementary information (ESI) available: UV–Vis spectrum of sample 3. See ht…
2002
Porous pure and doped silicas with pore sizes at two length scales (meso/macroporous) have been prepared and shaped both as powders and monoliths through a one-pot surfactant assisted procedure by using a simple template agent and starting from atrane complexes as inorganic precursors.
Organic Polyradicals as Redox Mediators: Effect of Intramolecular Radical Interactions on Their Efficiency
2020
The spin–spin interactions between unpaired electrons in organic (poly)radicals, especially nitroxides, are largely investigated and are of crucial importance for their applications in areas such as organic magnetism, molecular charge transfer, or multiple spin labeling in structural biology. Recently, 2,2,6,6-tetramethylpiperidinyloxyl and polymers functionalized with nitroxides have been described as successful redox mediators in several electrochemical applications; however, the study of spin–spin interaction effect in such an area is absent. This communication reports the preparation of a novel family of discrete polynitroxide molecules, with the same number of radical units but differe…
ZnO nanoparticles embedded in UVM-7-like mesoporous silica materials: Synthesis and characterization
2009
Abstract ZnO nanodomains embedded in bimodal mesoporous silica (UVM-7) materials with high Zn content (4≤Si/Zn≤30) have been synthesized by an one-pot surfactant-assisted procedure from a hydro alcoholic medium using a cationic surfactant (CTMABr=cetyltrimethylammonium bromide) as structural directing agent, and starting from molecular atrane complexes of Zn and Si as hydrolytic inorganic precursors. This chemical procedure allows optimizing the dispersion of the ZnO particles in the silica walls. The bimodal mesoporous nature of the final high surface area nano-sized materials is confirmed by XRD, TEM, and N2 adsorption–desorption isotherms. The small intra-particle mesopore system is due …
Layered-Expanded Mesostructured Silicas: Generalized Synthesis and Functionalization
2018
Mesostructured layered silicas have been prepared through a surfactant-assisted procedure using neutral alkylamines as templates and starting from atrane complexes as hydrolytic inorganic precursors. By adjusting the synthetic parameters, this kinetically controlled reproducible one-pot method allows for obtaining both pure and functionalized (inorganic or organically) lamellar silica frameworks. These are easily deconstructed and built up again, which provides a simple way for expanding the interlamellar space. The materials present high dispersibility, which results in stable colloidal suspensions.
Ordered mesoporous materials: composition and topology control through chemistry
2001
Abstract The atrane route constitutes a very versatile technique to obtain ordered mesoporous materials. A wide diversity of silica and silica-doped materials can be prepared by bringing into play fundamental synthesis parameters (like temperature, concentration and pH) which, in turn, allow modulation of the resulting material topology.
Supramolecular capping-ligand effect of lamellar silica mesostructures for the one-pot synthesis of highly dispersed ZnO nanoparticles
2006
ZnO?SiO2 lamellar nanocomposites with high zinc content (5?Si/Zn?50) have been synthesized through a one-pot surfactant-assisted procedure from aqueous solution and starting from molecular atrane complexes of Zn and Si as inorganic hydrolytic precursors. This approach allows optimization of the dispersion of the ZnO nanodomains in the silica sheets. The nature of the layered silica materials has been confirmed by x-ray diffraction. Spectroscopic (ultraviolet?visible and photoluminescence) study of these layered silica materials shows that, regardless of the Si/Zn ratio, Zn atoms are organized in well-dispersed, uniform ZnO nanodomains (about 1.2?nm) partially embedded within the silica shee…
Bases for the synthesis of nanoparticulated silicas with bimodal hierarchical porosity
2006
Porous silicas with pore sizes at two length scales (meso and large meso/macroporous) have been prepared through a one-pot surfactant assisted procedure by using a simple template agent and starting from silicon atrane complexes as hydrolytic inorganic precursors. The special organization of these bimodal porous silicas can be related to the nanometric character of their constituent mesoporous particles. Whereas the small intra-particle mesopore system is generated by the templating effect of the surfactant, the large pore system is defined by inter-particle voids. We have studied the effect of different procedural parameters on the small pore system and also on the nucleation and growth of…
Direct oxidation of isobutane to methacrolein over V-MCM-41 catalysts
2004
High vanadium content mesoporous vanado-silicates with MCM-41-like structure, obtained by the atrane route, catalyse the direct oxidation of isobutane to methacrolein with 30% selectivity, and a total dehydrogenation (olefin plus methacrolein) selectivity up to 74%.
Oxidomolybdenum(VI) complexes with atrane-type [O3N] ligands
2009
Abstract Dioxomolybdenum(VI) complex [MoO 2 Cl 2 (dmso) 2 ] reacts with a series of tetradentate O 3 N-type aminoalcohol–bisphenol ligands to form oxomolybdenum(VI) complexes of type [MoOCl(L n )]. The reaction of H 3 L 1 produces [MoOCl(L 1 )] as two separable isomers, whereas the reaction of H 3 L 2 or H 3 L 3 yields a single product. The X-ray analyses of cis - and trans -[MoOCl(L 1 )] reveal that the complexes are formed of monomeric molecules. The ligands have tetradentate coordination through three oxygen donors and one nitrogen donor, which is located trans to the terminal oxo group. The sixth coordination site is occupied by a chloro ligand.
High‐Zirconium‐Content Nano‐Sized Bimodal Mesoporous Silicas
2006
Silica-based nanoparticulated bimodal mesoporous materials with high Zr content (43 ≥ Si/Zr ≥ 4) have been synthesized by a one-pot surfactant-assisted procedure from a hydroalcoholic medium using a cationic surfactant (CTMABr = cetyltrimethylammonium bromide) as structure-directing agent, and starting from molecular atrane complexes of Zr and Si as hydrolytic inorganic precursors. This preparative technique allows optimization of the dispersion of the Zr guest species in the silica walls. The bimodal mesoporous nature of the final high surface area nano-sized materials is confirmed by XRD, TEM, and N2 adsorption–desorption isotherms. The small intraparticle mesopore system (with pore sizes…