Search results for "Spectroscopy"
showing 10 items of 10293 documents
Tin(IV) and organotin(IV) derivatives of bis(pyrazolyl)acetate: Synthesis, spectroscopic characterization and behaviour in solution.
2005
Abstract Novel heteroscorpionate-containing tin and organotin(IV) complexes, [SnRnX3 − n(L)], R = Me, Bun, Ph, or cy; X = Cl, Br or I, n = 0, 1, 2 or 3; L = bis(pyrazol-1-yl)acetate (bpza) or bis(3,5-dimethylpyrazol-1-yl)acetate (bdmpza), have been synthesized and characterized by spectral (IR, 1H, 13C and 119Sn NMR, 119mSn Mossbauer) and analytical data. In [SnI3(bdmpza)], the ligand is fac-N,N′,O-tridentate, the three iodine atoms thus also fac about the six-coordinate tin(IV) atom. Neutral bpzaH reacts with BunSnCl3, PhSnCl3 and SnCl4 in Et2O in the absence of base, yielding 1:1 adducts [XSnCl3(bpzaH)] (X = R or Cl).
Observations on the use of a sulfuric acid medium for As(V) to As(III) reduction in lodimetric titrations: Application to the determination of total …
1991
Abstract The use of a sulfuric rather than a hydrochloric acid medium for the reduction of As(V) to As(III) by iodide is proposed. Optimum conditions of acid concentration, amount of sodium hydroxide, and time and temperature are established to achieve quantitative reduction. The optimized reduction procedure was applied to the iodimetric determination of total arsenic and compared to a procedure that employs a hydrochloric acid medium. A systematic error of 0.04% was found for the method with a sulfuric acid medium opposed to 0.05% for the method with a hydrochloric acid medium in the reduction step. The proposed modified iodimetric method has been successfully used with some organic sampl…
Novel acrylamido monomers with higher hydrophilicity and improved hydrolytic stability: I. Synthetic route and product characterization.
1996
The novel acrylamido monomer reported by our group (N-acryloylaminoethoxyethanol, AAEE; Chiari et al., Electrophoresis 1994, 15, 177-186), found to combine high hydrophilicity with extraordinary resistance to alkaline hydrolysis, has come under closer scrutiny due to unexpected and random autopolymerization while stored as a 1/1 v/v water solution at 4 degrees C (possibly due to a greater oxidability of the ether group). We have additionally found a unique degradation pathway of the monomer, called "1-6 H-transfer", by which the C1 (on the double bond site), by constantly ramming against the C6, next to the ether oxygen (O7, which in fact favors the transfer of the hydrogen atom by C1), pro…
The guanidinium group as a key part of water-soluble polymer carriers for siRNA complexation and protection against degradation.
2014
Here, the preparation of a novel block copolymer consisting of a statistical copolymer N-(2-hydroxypropyl) methacrylamide-s-N-(3-aminopropyl) methacrylamide and a short terminal 3-guanidinopropyl methacrylamide block is reported. This polymer structure forms neutral but water-soluble nanosized complexes with siRNA. The siRNA block copolymer complexes are first analyzed using agarose gel electrophoresis and their size is determined with fluorescence correlation spectroscopy. The protective properties of the polymer against RNA degradation are investigated by treating the siRNA block copolymer complexes with RNase V1. Heparin competition assays confirm the efficient release of the cargo in vi…
Reactive surface coatings based on polysilsesquioxanes: defined adjustment of surface wettability.
2009
We have investigated a generally applicable protocol for a substrate-independent reactive polymer coating that offers interesting possibilities for further molecular tailoring via simple wet chemical derivatization reactions. Poly(methylsilsesquioxane)-poly(pentafluorophenyl acrylate) hybrid polymers have been synthesized by RAFT polymerization, and stable reactive surface coatings have been prepared by spin-coating on the following substrates: Si, glass, gold, PMMA, PDMS, and steel. These coatings have been used for a defined adjustment of surface wettability by surface-analogous reaction with various amines (e.g., glutamic acid to obtain hydrophilic surfaces (Theta(a) = 18 degrees) or per…
Resorcinarene-based ATRP initiators for star polymers
2004
Two novel multifunctional initiators for atom transfer radical polymeriza- tion (ATRP) were synthesized by derivatization of tetraethylresorcinarene. The deri- vatization induced a change in the conformation of the resorcinarene ring, which was confirmed by NMR spectroscopy. The initiators were used in ATRP of tert-butyl acrylate and methyl methacrylate, producing star polymers with controlled molar masses and low polydispersities. Instead of the expected star polymers with eight arms, polymers with four arms were obtained. Conformational studies on the initiators by rotating- frame nuclear Overhauser and exchange spectroscopy NMR and molecular modeling suggested that of eight initiator fun…
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…
Electrospray ion mobility mass spectrometry of positively and negatively charged (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium br…
2015
Rationale Self-assembling processes of surfactants in the gas phase constitute a developing research field of interest since they allow information to be gained on the peculiar structural organization of these aggregates, on their ability to incorporate from small molecules up to proteins and on their possible use as carriers of drugs in the gas phase or as cleaning agents and exotic reaction media. Methods The mass spectra of charged aggregates of the chiral surfactant (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) in the gas phase have been recorded using a Synapt G2-Si mass spectrometer in the positive and negative ion mode. For comparison purposes, the …
Structure and Shear Response of Janus Colloid–Polymer Mixtures in Solution
2020
We investigate the structure and rheological properties of dilute colloid-polymer mixtures at rest and under shear via molecular simulations that take into account hydrodynamic interactions. Mixtures of amphiphilic Janus colloids (JCs) and hydrophobic/amphiphilic polymers are considered for various solvent qualities and polymer concentrations. Free polymers, small polymer droplets, and hybrid aggregates coexist in mixtures with slightly hydrophobic homopolymers. As the solvent quality worsens, all polymers aggregate into small droplets, covered and stabilized by the JCs. In mixtures with amphiphilic polymers, we observe the coexistence of free polymers, purely polymeric micelles, and hybrid…