Search results for "MOLECULE"
showing 10 items of 5162 documents
Gas phase charged aggregates of bis(2-ethylhexyl)sulfosuccinate (AOT) and divalent metal ions: first evidence of AOT solvated aggregates
2011
Assembling and chelating properties of sodium bis(2-ethylhexyl)sulfosuccinate (AOTNa) towards divalent metal ions have been investigated in the gas phase by electrospray ionization mass spectrometry. A variety of positively charged monometallated and mixed metal aggregates are formed. Interestingly, several ions contain solvent (MeOH, H2O) molecules and constitute the most abundant AOT cationic aggregates not containing sodium. These species are the first example of solvated AOT-metal ion aggregates in the gas phase. By increasing the surfactant aggregation number, the abundance of solvated species becomes lower than that of unsolvated ones. Decompositions of ionic species have been studied…
Self-assembly and intra-cluster reactions of erbium and ytterbium bis(2-ethylhexyl)sulfosuccinates in the gas phase
2014
RATIONALE The study of surfactant organization in vacuum allows surfactant–surfactant interaction to be unveiled in the absence of surrounding solvent molecules. Knowledge on their chemical-physical properties may also lead to the definition of more efficient gas-phase carriers, air-cleaning agents and nanoreactors. In addition, the presence of lanthanide-group ions adds unique photochemical properties to surfactants. METHODS The structural features, stability and fragmentation patterns of charged aggregates formed by lanthanide-functionalized surfactants, ytterbium and erbium bis(2-ethylhexyl)sulfosuccinate ((AOT)3Yb and (AOT)3Er), have been investigated by electrospray ionization mass spe…
Spatially ordered surfactant assemblies in the gas phase: negatively charged bis(2-ethylhexyl)sulfosuccinate-alkaline metal ion aggregates
2009
The formation and structural features of negatively charged aggregates of sodium bis(2-ethylhexyl)sulfosuccinate (AOTNa) surfactant molecules in the gas phase have been investigated by electrospray ionization mass spectrometry (ESI-MS) and density functional theory calculations. Mainly driven by the interactions of alkali metal ions both with the oxygen atoms of the sulfonate group and with the succinate moiety of the AOT− anion, spatially ordered supramolecular assemblies, characterized by an internal core composed of surfactant counterions and hydrophilic head groups surrounded by the surfactant alkyl chains pointing outwards, are formed. Calculations have shown that surfactant self-organ…
Stereoselective Synthesis of the Glycosidase Inhibitor Australine through a One-Pot, Double-Cyclization Strategy
2006
[reaction: see text] A stereocontrolled, convergent synthesis of the alkaloid australine, a glycosidase inhibitor of the pyrrolizidine class, is described. The chiral starting materials were ketone 3, derived from L-erythrulose, and alpha-alkoxy aldehyde 4, prepared from L-malic acid. A key step of the synthesis was the highly stereoselective aldol reaction between 4 and a Z boron enolate derived from 3. Another key step was the one-pot construction of the bicyclic pyrrolizidine system by means of a three-step sequence of SN2 displacements induced by benzylamine on a trimesylate precursor.
Tungsten oxides as catalysts in selective oxidation
1983
Abstract The reaction of allyl iodide was studied at the surface of four tungsten oxides and molybdenum trioxide. On WO2.95 and MoO3, in which crystallographic shear structures are formed on reduction, acrolein is produced at 300–400 °C, whereas W18O49 and WO2, which do not show this property, are inactive, as is WO3. It is concluded that the transformation of a corner-linked into an edge-linked arrangement of metal-oxygen octahedra provides a facile route for insertion of oxygen into a hydrocarbon molecule.
ChemInform Abstract: Diastereoselective Intramolecular Additions of Allyl- and Propargylsilanes to Iminium Ions: Synthesis of Cyclic and Bicyclic Qua…
2010
Cyclization of the chiral imino lactones with allylic or propargylic groups required acidic conditions to afford spirocyclic (II) or (XII).
Selective Transformation of Norbornadiene into Functionalized Azaheterocycles and β‐Amino Esters with Stereo‐ and Regiocontrol
2021
Novel functionalized azaheterocycles with multiple chiral centers have been accessed from readily available norbornene β-amino acids or β-lactams across a stereocontrolled synthetic route, based on ring-opening metathesis (ROM) of the staring unsaturated bicyclic amino esters, followed by selective cyclization through ring-closing metathesis (RCM). The RCM transformations have been studied under various experimental conditions to assess the scope of conversion, catalyst, yield, and substrate influence. The structure of the starting norbornene β-amino acids predetermined the structure of the new azaheterocycles, and the developed synthetic route took place with the conservation of the config…
Fluorescence and amplified spontaneous emission of glass forming compounds containing styryl-4H-pyran-4-ylidene fragment
2012
Potential of glassy films of newly synthesised low molecular weight organic molecules for light amplification and lasing applications has been investigated by analysing fluorescence, transient differential absorption and amplified spontaneous emission properties. These non-symmetric and symmetric molecules contain styryl-4H-pyran-4-ylidene fragment with three different electron acceptor groups: dicyanomethylene, barbituric acid, indene-1,3-dione. Fluorescence quantum yields of the investigated compounds in solutions are between 0.32 and 0.54, while they drop down by an order of magnitude in thin solid films. Incorporation of bulky side groups reduced excitonic interactions enabling manifest…
Glassy 2-(1-benzyl-2-styryl-6-methylpyridin-4(1H)-ylidene) fragment containing 1H-indene-1,3(2H)-dione and pyrimidine-2,4,6(1H,3H,5H)-trione derivati…
2020
A series of 2-(1-benzyl-2-(styryl)-6-methylpyridin-4(1H)-ylidene) fragment containing glassy organic compounds have been synthesized from relevant luminescent 4H-pyran-4-ylidene derivatives and investigated as potential solution processable emitters. Glass transition temperatures of synthesized 1H-pyridine compounds are above 100°C with thermal stabilities higher than 260°C. In the solutions of dichloromethane their absorption bands are in the range from 350 nm to 500 nm with photoluminescence from 500 nm to 650 nm. In a contrary to the 4H-pyran-4-ylidene derivatives, the incorporation of various electron acceptor fragments within the 1H-pyridine fragment containing molecules only slightly …
Photo-inhibition of Ab fibrillation mediated by a newly designed fluorinated oxadiazole
2015
Uncontrolled aggregation of amyloid beta peptide (A?) is the main cause of Alzheimer's Disease. Therapeutic approaches of intervention in amyloid diseases include the use of small molecules able to stabilize the soluble A? conformation, or to redirect the amyloidogenic pathway towards non-toxic and non-fibrillar states. Fluorometric measurements revealed that the 3-(4'-trifluoromethylphenyl)-5-(4'-methoxyphenyl)-1,2,4-oxadiazole, when irradiated, is able to interact with monomeric A? peptide readdressing the aggregation pathway toward the formation of amorphous aggregates as evidenced by means of CD, AFM, and SAXS measurements. We hypothesize that this compound, under radiation, forms a rea…