Search results for "Mono"
showing 10 items of 6843 documents
Investigation of polymers in the mass spectrometer, 7. Pyrolysis-gas chromatography-mass spectrometry of low molecular and high polymeric sulfanilami…
1975
A number of low molecular, monomeric and polymeric sulfanilamide derivatives, which have found interest as possibly selective antitumour agents, were investigated by pyrolysis-gas chromatography (GC)-mass spectrometry (MS). Thermal degradation mechanisms were studied using also direct polymer pyrolysis in the ion source of the mass spectrometer. Thermal degradation products as well as low molecular weight sulfanilamides and related model compounds were characterized in their fragmentation behaviour by low and high resolution electron impact and field desorption mass spectrometry. Thermal fragments of structural significance were found, and a differentiation of the low and high molecular sul…
Trapping Rare and Elusive Phosphinidene Chalcogenides
2017
Four-membered rings with a P2Ch2 core (Ch=S, Se) and phosphorus in the +3 oxidation state have been synthesized. The utility of these rings as a source of monomeric phosphinidene chalcogenides was probed by the addition of an N-heterocyclic carbene, resulting in a base-stabilized phosphinidene sulfide. Similarly, persistence of the phosphinidene selenide in solution was shown through cycloaddition chemistry with 2,3-dimethylbutadiene at elevated temperatures. The observed reactivity was explained by detailed computational work that established the conditions upon which the P2Ch2 rings can liberate phosphinidene chalcogenides. peerReviewed
Copper(II) complexes with sulfonamides derived from 2-picolylamine and their use as chemical nucleases
2006
Reaction between 2-picolylamine (2-aminomethylpyridine) with 2-mesitylenesulfonyl and 4- tert -butylbenzene sulfonyl chlorides leads to the formation of 2,4,6-trimethyl- N -[pyridin-2-ilmethyl]benzenesulfonamide (Hpmesa) and 4-ter-butyl- N -[pyridin-2-ilmethyl]benzenesulfonamide (Hptbsa). These compounds react with Cu(II) salts to yield coordination compounds with CuL 2 stoichiometry. The immediate environment of the metal ion is a highly distorted tetrahedron, the sulfonamide ligands acting in a bidentate fashion. Compound Hpmesa crystallizes in monoclinic space group P 2 1 /c (number 14), with Z = 4; complex [Cu(pmesa) 2 ] crystallizes in monoclinic space group P 1 ¯ (number 2), with Z …
N-p-Amino- and N-p-nitro-phenylsulfonyl derivatives of dipeptides, a new family of ligands for copper(II). Potentiometric and spectroscopic studies
1995
The co-ordination ability of four dipeptide analogues substituted on the N-terminal amino group with p-nitrophenylsulfonyl (nps-Ala-Ala and nps-Ala-His) and p-aminophenylsulfonyl (aps-Ala-Ala and aps-Ala-His) groups was studied by potentiometric and spectroscopic (UV/VIS absorption, CD and EPR) techniques. The N-terminal sulfonyl substituent drastically changes the acidity of the sulfonamide proton making nitrogen very efficient in binding to CuII. The sulfonamide nitrogen having pK between 9 and 11 does not need any anchoring binding group to form complexes with CuII. The para substituent on the phenyl ring (amino or nitro) influences very strongly the acidity of the sulfonamide proton. Th…
Enzymic Control of Reactive Metabolites from Aromatic Carcinogens
1980
Mutation and transformation in C3H 10T 1/2 mouse fibroblasts were coordinately induced by 4-nitroquinoline N-oxide and identically modulated by caffeine strongly suggesting mutation as one necessary step in the sequence of events ultimately leading to transformation. The enzymic control of reactive metabolites derived from aromatic carcinogens was then investigated using bacterial mutagenicity as an analytical tool. It was shown that the correlation of bacterial mutagenicity with carcinogenicity of BP and four major metabolites was substantially better when these compounds were activated by intact hepatocytes as compared to commonly used broken cell preparations which suggests that the rela…
Modulation of the Electronic Properties in Polydithienotiiophene Materials
1997
AbstractConjugated polymers with narrow band gap are promising candidates for symmetric electrochemical devices, such as electrochromics and redox supercapacitors, which involve the pand n-doped state of the polymer. Polydithienothiophene materials which are prepared from isomer monomers show this characteristic. The copolymerisation of two dithienothiophene isomers leads to materials whose electronic properties depend on the monomer ratio. Optical and electrochemical characterizations of different copolymers are reported and discussed.
A green route to synthesize poly(lactic acid)-based macromonomers in scCO2 for biodegradable nanoparticle production
2014
Poly(lactic acid)-based macromonomers, aimed at biomedical applications and with well-defined average chain length, are produced through catalytic ring-opening polymerization of L,L-lactide co-initiated by a co-monomer bearing a double bond. Reactions have been carried out in supercritical carbon dioxide (scCO2) at different temperatures, ranging from 90 to 130 °C. The resulting oligomers have been characterized by different techniques (1H-NMR, 13CNMR, MALDI-TOF, ESI, GPC, FT-IR, TGA), which show that oligomers with narrower molecular weight distribution are produced at the lowest temperature. In addition, a significant reduction of the impact of the secondary reactions has been found at th…
Impact of the reaction pathway on the final product in on-surface synthesis
2020
International audience; On-surface synthesis provides a very promising strategy for creating stable functional structures on surfaces. In the past, classical reactions known from solution synthesis have been successfully transferred onto a surface. Due to the presence of the surface, on-surface synthesis provides the potential of directing the reaction pathway in a manner that might not be accessible in classical solution synthesis. In this work, we present evidence for an acetylene polymerization from a terminal alkyne monomer deposited onto calcite (10.4). Strikingly, although the dimer forms on the surface as well, we find no indication for diacetylene polymerization. This is in sharp co…
Kinetically Controlled Sequential Growth of Surface-Grafted Chiral Supramolecular Copolymers.
2016
We report a facile strategy to grow supramolecular copolymers on Au surfaces by successively exposing a surface-anchored monomer to solutions of oppositely charged peptide comonomers. Charge regulation on the active chain end of the polymer sufficiently slows down the kinetics of the self-assembly process to produce kinetically trapped copolymers at near-neutral pH. We thereby achieve architectural control at three levels: The β-sheet sequences direct the polymerization away from the surface, the height of the supramolecular copolymer brushes is well-controlled by the stepwise nature of the alternating copolymer growth, and 2D spatial resolution is realized by using micropatterned initiatin…
Hetero-Multifunctional Poly(ethylene glycol) Copolymers with Multiple Hydroxyl Groups and a Single Terminal Functionality
2009
Hetero-multifunctional poly(ethylene glycol-co-glycerol) random copolymers with multiple hydroxyl functionalities and a single terminal functionality have been prepared by copolymerization of ethylene oxide (EO) and ethoxy ethyl glycidyl ether (EEGE) with the use of a suitable initiator, introducing a protected amino group or a double bond, respectively. Acidic deprotection was used for removal of the acetal protecting groups in the chain, and the terminal amino group was regenerated by catalytic hydrogenation. A series of copolymers with narrow polydispersity was obtained, varying comonomer fractions from 3 to 67% and molecular weights in the range of 5 000-32 000 g · mol(-1) (1.05 < $\ove…