Electrochemical oxidation of aliphatic amines and their attachment to carbon and metal surfaces

The electrochemical oxidation of aliphatic amines (primary, secondary, and tertiary) has been investigated by cyclic voltammetry and preparative electrolysis. The oxidation mechanisms have been established, and the lifetimes of the radical cations have been measured for secondary and tertiary amines. These results have been put in parallel with the attachment of amines to glassy carbon, Au, and Pt electrodes by cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and infrared reflection-absorption spectroscopy (IRRAS). It is then possible to show that it is not the radical cation but the radical obtained after the deprotonation which reacts with the electrode surface. XPS results also point to the existence of a covalent bond between Au or Pt and the organic moiety.     

Synthesis, characterization and potential biomedical applications of N-succinimidyl ester functionalized, polypyrrole-coated polystyrene latex particles

N-Succinimidyl ester functionalized polypyrrole-coated polystyrene latex particles (PS_E-PPyNSE) were prepared by the in situ copolymerization of pyrrole and the active ester-functionalized pyrrole (pyrrole-NSE) in the presence of polystyrene latex particles. Polystyrene microspheres were prepared by emulsion polymerization (PS_E) leading to particles having a diameter of 450 nm. These PS_E particles were precoated with poly(N-vinylpyrrolidone) prior to the in situ copolymerization of pyrrole and pyrrole-NSE. The initial comonomer concentration fractions were 25/75, 50/50 and 75/25 for pyrrole and pyrrole-NSE, respectively. The PPy-coated PS_E particles were characterized in terms of morphology, particle size, electrophoretic mobility and chemical composition. The study of morphology by means of scanning electron microscopy showed roughening of the underlying PS_E particles owing to the addition of PPyNSE, the overlayer thickness of which was estimated to be around 7 nm. Moreover, loading PPyNSE overlayers resulted in a shift of the electrophoretic mobility from –5.31 m cm/V s to a very small but positive value (0.082–0.112 m cm/V s). X-ray photoelectron spectroscopy and IR spectroscopy permitted the detection of pyrrole-NSE repeat units at the surface indicating that pyrrole and pyrrole-NSE did indeed copolymerize. The PS_E-PPyNSE particles were further evaluated as bioadsorbents of human serum albumin used as a test protein. For this study, PS_E-PPyNSE₅₀ particles, synthesized from a comonomer feed ratio of 50/50 in pyrrole/pyrrole-NSE, were used and were shown to attach efficiently human serum albumin macromolecules with a maximum amount of 0.2 mg m^–2.

Synthèse du mèthyl-1 diformyl-2,3 pyrrole,de la méthyl-1 pyrrolo[2,3-d] pyridazine et de la méthyl-1 oxo-6 (6h)cycloheptatrieno[b] pyrrole

This communication describes the synthesis of l-methyl-2,3-diformylpyrrole. This new compound is used to prepare a new heterocycle, l-methylcyclohepta[b]pyrrol-6-one and thus allows a new synthesis of l-methylpyrrolo[2,3-d]pyridazine.     

Synthesis and characterization of active ester-functionalized polypyrrole-silica nanoparticles: application to the covalent attachment of proteins

Novel ester-functionalized polypyrrole-silica nanocomposite particles were prepared by oxidative copolymerization of pyrrole and N-succinimidyl ester pyrrole (50/50% initial concentrations), using FeCl3 in the presence of ultrafine silica nanoparticles (20 nm diameter). The N-succinimidyl ester pyrrole monomer was prepared in aqueous solution using 1-(2-carboxyethylpyrrole) and N-hydroxysuccinimide in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. The resulting nanocomposites (N-succinimidyl ester polypyrrole-silica) are raspberry-shaped agglomerates of silica sol particles "glued" together by the insoluble poly(pyrrole-co-N-succinimidyl pyrrole). The N-succinimidyl ester polypyrrole-silica particles were characterized in terms of their size, density, copolymer content, and polydispersity. Scanning electron microscopy and disk centrifuge sedimentometry confirmed that the nanocomposite particles had narrow size distributions. X-ray photoelectron spectroscopy analysis indicated a silica-rich surface and a high surface concentration of N-succinimidyl ester groups. These nanoparticles exhibited good long-term dispersion stability. The chemical stability of the ester functions in aqueous media after several weeks of storage was monitored by FTIR spectroscopy. The functionalized nanocomposites were tested as bioadsorbents of human serum albumin (HSA). The very high amount of immobilized HSA determined by UV-visible spectroscopy is believed to be due to covalent binding. Incubation of the HSA-grafted nanocomposite with anti-HSA resulted in immediate flocculation, an indication that they are alternative candidates for visual diagnostic assays.     

X‐ray induced degradation of surface bound azido groups during XPS analysis

Mesoporous silica SBA‐15 was synthesized and silanized with azidopropyl triethoxysilane in order to design a clickable material. Fourier transform infrared analysis permitted to prove the attachment of the azidopropylene groups to SBA‐15 resulting in the reactive and functional material N₃‐SBA‐15. X‐ray photoelectron spectroscopy was used to determine the surface composition of SBA‐15. However, we unexpectedly found that the surface bound azido groups undergo X‐ray induced decomposition during the X‐ray photoelectron spectroscopy analysis resulting in the formation of nitrenes. These are very reactive groups able to intercalate C―C and C―H bonds of the propylene chains as judged from the N1s peak shape. Possible mechanisms of intercalation are suggested. C1s and N1s peaks were recorded at different exposure time. N/C, N⁺/N and N⁺/C undergo exponential decay. N⁺/N reaches the value of zero in less than 80 min of exposure to the X‐ray source. The N⁺/C decay plot was fitted with first‐order kinetics, and the decomposition kinetic constant (k_dec) was found to equal to 516.4 s^?1. This is a fast X‐ray induced degradation which must be considered with care when examining clickable materials with surface bound alkyl azido groups. Copyright © 2016 John Wiley & Sons, Ltd.     

X-ray photoelectron spectroscopy of merocyanine dyes Part VIII. Partial charge and conjugation of heteroatoms in the electroattractor rings

Partial charges for oxygen and sulfur in the electroattractor rings of a series of merocyanine dyes are determined using binding energy-partial charge correlations. The atomic charges are used to study the conjugation of the heteroatoms in the electroattractor part of the dyes. The carbonyl group is highly conjugated in the C-O⁻ form, especially in the nitro dyes, whereas its conjugation is somewhat hindered when a thioketone group coexists in the attractor part, thus suggesting a competition between both attractor groups.     

Synthesis,characterization and applications of polysiloxane networks with immobilized pyrogallol ligands

A porous, solid insoluble polysiloxane‐immobilized ligand system bearing pyrogallol active sites of the general formula P? (CH₂)₃? NH(CH₂)₃OC₆H₃(OH)₂ (where P represents [Si? O]_n siloxane network) has been prepared by the reaction of 3‐aminopropylpolysiloxane with 1,3‐dibromopropane followed by the reaction with pyrogallol. ¹³C CP‐MAS NMR and X‐ray photoelectron spectroscopy confirmed that the pyrogallol is chemically bonded to the siloxane backbone. Thermal analysis showed that the ligand system is stable under nitrogen at relatively high temperature. The polysiloxane–pyrogallol ligand system exhibits high potential for the uptake of the metal ions (Fe³⁺, Co²⁺, Ni²⁺ and Cu²⁺). Complexation of the pyrogallol ligand system for the metal ions at the optimum conditions was found to be in the order Fe³⁺ > Cu²⁺ > Ni²⁺ > Co²⁺. Copyright © 2005 John Wiley & Sons, Ltd.