Search results for "DEP"
showing 10 items of 10555 documents
Coordination chemistry of N,N′-bis(coordinating group substituted)oxamides: a rational design of nuclearity tailored polynuclear complexes
1999
Abstract The coordinating properties of N , N ′-bis(coordinating group substituted)oxamides have been thoroughly investigated both in aqueous solution and in the solid state. The easy cis – trans isomerization equilibria that they exhibit together with the great variety of N , N ′-substituents which can be used to play on the overall charge, complexing ability and polarity, make them very suitable ligands in designing homo- and heterometallic species. The knowledge of their complex formation in aqueous solution by potentiometry and using the hydrogen ion concentration as a probe, allowed us to settle the basis of a rational design of oxamidate-containing polynuclear species whose nuclearity…
Synthesis of gold nanotubes with variable wall thicknesses
2013
We report the synthesis of gold nanotubes with variable wall thicknesses that is accomplished by the deposition of sacrificial hydrophobic polymer cores followed by gold shells within an anodic aluminum oxide template. We demonstrate that by varying polymer core hydrophobicity, the resulting gold shell thickness can be varied. There are two requirements for gold shell formation: (1) the polymer core must be able to be electrodeposited into a tubular (as opposed to wire-like) structure, and (2) the polymer must be hydrophobic, such that it collapses upon exposure to an aqueous solution. An array of gold nanotubes has variable plasmonic properties and can function as a surface enhanced Raman …
A new class of ZnIIand CrIIIporphyrins incorporated into porous polymer matrices via an atmospheric pressure plasma enhanced CVD to form gas sensing …
2014
Designed ZnII and CrIII porphyrins (ZnIIP, CrIIIP(Cl)(H2O)) and conventional ZnIITPP and CrIIITPP(Cl)(H2O) are immobilized into porous polysiloxane films via chemical vapor deposition enhanced by an atmospheric pressure dielectric barrier discharge. UV/vis spectroscopy and mass spectrometry prove the integrity of the chromophores after the plasma treatment. The optical amine sensing capabilities of the films are investigated spectroscopically on exposure to triethylamine vapors. A series of coatings with different porphyrin loadings indicate influences of the deposition conditions on the growth of the sensing films and hence the device performance. Additionally, the synthesis and characteri…
Increased Acid Dissociation at the Quartz/Water Interface.
2018
As shown by a quite significant amount of literature, acids at the water surface tend to be “less” acid, meaning that their associated form is favored over the conjugated base. What happens at the solid/liquid interface? In the case of the silica/water interface, we show how the acidity of adsorbed molecules can instead increase. Using a free energy perturbation approach in combination with electronic structure-based molecular dynamics simulations, we show how the acidity of pyruvic acid at the quartz/water interface is increased by almost two units. Such increased acidity is the result of the specific microsolvation at the interface and, in particular, of the stabilization of the deprotona…
Deprotonation of Fluoro Aromatics Using Lithium Magnesates.
2004
Abstract 3-Fluoropyridine was deprotonated on treatment with 1/3 equiv of Bu 3 MgLi in THF at −10 °C. The lithium arylmagnesate formed was either trapped with electrophiles or involved in a palladium-catalyzed cross-coupling reaction with 2-bromopyridine. The use of a less nucleophilic lithium-magnesium-dialkylamide, (TMP) 3 MgLi, allowed the reaction of 3-fluoroquinoline, giving the 2,2′-dimeric derivative. 2-Fluoropyridine and 2,6-difluoropyridine were deprotonated using 1/3 equiv of the highly coordinated magnesate Bu 4 MgLi 2 in THF at −10 °C in the presence of a substoichiometric amount of 2,2,6,6-tetramethylpiperidine. 1,3-Difluorobenzene reacted similarly when treated with Bu 3 MgLi;…
Group 13 complexes of dipyridylmethane, a forgotten ligand in coordination chemistry.
2015
The reactions of dipyridylmethane (dpma) with group 13 trichlorides were investigated in 1 : 1 and 1 : 2 molar ratios using NMR spectroscopy and X-ray crystallography. With 1 : 1 stoichiometry and Et2O as solvent, reactions employing AlCl3 or GaCl3 gave mixtures of products with the salt [(dpma)2MCl2](+)[MCl4](-) (M = Al, Ga) as the main species. The corresponding reactions in 1 : 2 molar ratio gave similar mixtures but with [(dpma)MCl2](+)[MCl4](-) as the primary product. Pure salts [(dpma)AlCl2](+)[Cl](-) and [(dpma)AlCl2](+)[AlCl4](-) could be obtained by performing the reactions in CH3CN. In the case of InCl3, a neutral monoadduct (dpma)InCl3 formed regardless of the stoichiometry emplo…
Modelling of natural synthetic polyelectrolyte interactions in natural waters by using SIT, Pitzer and Ion Pairing approaches
2006
Abstract In this paper SIT and Pitzer models are used for the first time to describe the interactions of natural and synthetic polyelectrolytes in natural waters. Measurements were made potentiometrically at 25 °C in single electrolyte media, such as Et 4 NI and NaCl (for fulvic acid 0.1 − 1 S single salt ” BA, with cation B and anion A representing all the major cations (Na + , K + , Mg 2+ , Ca 2+ ) and anions (Cl − , SO 4 2− ) in natural sea water, respectively. The ion pair formation model was also applied to fulvate and alginate in artificial sea water by examining the interaction of polyanions with the single sea water cation. Results were compared with those obtained from previous sp…
Vapor Pressures of Polymer Solutions and the Modeling of Their Composition Dependence
2009
Equilibrium vapor pressures, p, are reported for the systems tetrahydrofuran + poly(vinyl methyl ether) and tetrahydrofuran + polystyrene at 20, 40, and 60 °C. These data plus information from the literature serve to demonstrate that the composition dependence of p can be modeled quantitatively for polymer solutions in thermodynamically very different solvents by means of three, physically meaningful parameters.
Synthesis, structure and physical characterization of the dimer {[(bpy)2Co]2(TPOA)}4+ (bpy=2,2′-dipyridyl; H2TPOA=N,N′,N′′,N′′′-tetraphenyl oxalamidi…
2008
Abstract The reaction between CoCl 2 , 2,2′-dipyridyl (bpy) and N , N ′, N ′′, N ′′′-tetraphenyl oxalamidine (H 2 TPOA) in a water/ethanol mixture yields the {[(bpy) 2 Co] 2 (TPOA)} 2+ dimer, that is immediately oxidized in aerobic conditions leading to the Co III species {[(bpy) 2 Co] 2 (TPOA)} 4+ . This cation was isolated as the {[(bpy) 2 Co] 2 (TPOA)}(PF6) 4 ( 1 ) salt, that was characterized by X-ray diffraction on single crystals. The dimer is formed by two Co III ions in octahedral coordination bridged by a deprotonated μ 2 -TPOA ligand. The Co III ions appear in its low spin configuration. Thus, the dimers are essentially diamagnetic, as shown by 1 H NMR and magnetic measurements.
Configuration of Enolates of β-Ketocarboxylic Acid Esters — Carbocation-Carbanion Salts
1996
Deprotonation of (Z)- or (E)-3-hydroxy-2,3-dimesitylpropenoic acid methyl ester (1a) with tetrakis(dimethylamino)-methane (3) led to stable salt (E)-2a, which belongs to a very rare species of salts that consist of a heteroatom-stabilized carbocation and a heteroatom-stabilized carbanion. An analogous guanidinium salt (E)-2b was formed in the reaction of 3-oxo-2,3-diphenylpropanoic acid methyl ester (1b) and 3. The molecular structures of these enolates were studied by NMR spectroscopy and an X-ray analysis of (E)-2a {MC[N(CH3)2]3} and compared with those of the corresponding alkali enolates.