Hydroformylation of styrene catalyzed by a rhodium thiolate binuclear catalyst supported on a cationic exchange resin

The binuclear complex [Rh₂(μ-S(CH₂)₂NMe₂)₂(cod)₂] 1 (cod=1,5-cyclooctadiene) was anchored to a sulfonic exchange resin through the residual amine groups. The reaction of the immobilized complex with CO and PPh₃ yielded the catalytically active complex [Rh₂(μ-S(CH₂)₂NHMe₂)₂(CO)₂(PPh₃)₂]²⁺ supported in the polymer matrix. When methanol was used as solvent, the metal complex loaded cationic resin behaved as a multifunctional catalyst, since it was active in the hydroformylation of styrene and the subsequent formation of the acetals, directly rendering 1,1-dimethoxy-2-phenylpropane in 85% selectivity. Furthermore, the immobilized catalyst can be separated from the reaction mixture and recycled. A homogeneous model of the supported catalyst was generated by reacting complex 1 with HTsO, PPh₃, and CO. Thus, the methanol soluble complex [Rh₂(μ-S(CH₂)₂NHMe₂)₂(CO)₂(PPh₃)₂](TsO)₂ was also found to be active in the hydroformylation of styrene yielding identical selectivity in the branched isomer to that of the immobilized catalyst, although the latter is much slower (20-fold) than the homogeneous catalyst.     

Nanopowders by Organic Polymerisation

The acrylamide sol-gel processes becomes a fast, cheap, reproducible and easy to scale-up chemical way for obtaining nanopowders of BaZrO₃, which can be used for crucible sintering or many electronic applications. This synthesis method allows performing 100 g of high purity nanosized particles, in one run, with simple laboratory equipment and using low cost raw materials. Temperature synthesis and atmosphere conditions are studied for obtaining best powders. They are sintered at 1450°C to full density, then at much lower temperature than previously reported, making possible the crucible fabrication of BaZrO₃ for many laboratories.     

Effect of organic matter on the in vitro photoeradication of Pseudomonas aeruginosa by means of a cationic tetraaryl-porphyrin

Photodynamic therapy is emerging as an antimicrobial alternative approach; the concomitant presence of a photosensitizer (PS), O(2) and visible light induces lethal oxidative damages to bacterial cells. Among Gram-negative bacteria, Pseudomonas aeruginosa seems to be one of the least susceptible to photodynamic treatment. In this study, we evaluated the influence of several experimental conditions on photoeradication of a planktonic culture of P. aeruginosa PAO1 by means of a tetracationic meso-arylsubstituted porphyrin (RM24). Our findings suggest that the photo-oxidative stress induced by RM24 is strictly correlated to the amount of PS bound to the cells that in turn decreases with the increasing concentrations of organic compounds in the medium. The photoeradication is dependent on PS concentrations, cellular density and light dose. RM24 was able to induce oxidative stress by means of singlet oxygen formation, although ROS formation cannot be ruled out. The standardized experimental conditions of the photospot test allowed us to evidence intraspecific PDT sensitivity differences among three strains of P. aeruginosa.     

Kinetics of fast-curing epoxy resin cationic thermopolymerization: Propagated by ACE and AM mechanism

Journal of Thermal Analysis and Calorimetry - The kinetics of fast thermal curing epoxy resin and the fast-curing ability initiated by 4- hydroxyphenyl dialkyl sulfonium salt cationic curing agent...     

Synthesis and investigation of the efficiency of cationic aminopolymer resin

Experimental results of synthesis and investigation of the efficiency of a cationic aminopolymer resin are presented. The monomers are characterized, the synthesis conditions are considered, and the technical characteristics of the resin are given. It is shown that the resin facilitates the acceleration of dehydration of repulped stock, significantly reduces the cationic need, increasing the retention of anionic contaminations, and decreases the content of suspended substances in recycled water. The data on pilot tests of the resin are presented that demonstrate its high efficiency.     

Selenium determination by HG-ICPAES: Elimination of iron interferences by means of an ion-exchange resin in a continuous flow system

 An accurate procedure for the elimination of iron interferences in the determination of selenium in geological materials by the Hydride Generation – Inductively Coupled Plasma Atomic Emission Spectrometry technique (HG-ICPAES) is proposed. A selective removal of iron is achieved by on-line incorporation of a microcolumn filled with strongly acidic cation exchange resin (Dowex 50W-X8). The microcolumn manifold used was interfaced with the hydride generation manifold by a flow injection sample injection valve. After the removal of the iron, a 500 μl sample was injected into a carrier stream of water. This was merged with hydrochloric acid and sodium tetrahydroborate in order to generate the corresponding selenium hydride. The system was found to have a limit of detection of 0.4 ng ml^-1 and a relative standard deviation of 2% for 20 ng ml^-1 selenium. The application of the method on different Geochemical Standard Reference Samples demonstrated that results were statistically indistinguishable from certified values. Received: 7 March 1996 / Revised: 30 May 1996 / Accepted: 4 June 1996     

Separation of palladium(II) and platinum(II) chlorides by means of a guanidine resin

The preparation and properties of a new, weakly basic ion-exchanger containing suilonylguanidine as the active groups are described. Palladium and platinum chlorides can be quantitatively separated by this resin. Under certain conditions platinum does not react with the resin, whereas palladium is adsorbed and can then be eluted with 3 M hydrochloric acid.     

Iron-Catalysed Radical Polymerisation by Living Bacteria

The ability to harness cellular redox processes for abiotic synthesis might allow the preparation of engineered hybrid living systems. Towards this goal we describe a new bacteria-mediated iron-catalysed reversible deactivation radical polymerisation (RDRP), with a range of metal-chelating agents and monomers that can be used under ambient conditions with a bacterial redox initiation step to generate polymers. Cupriavidus metallidurans, Escherichia coli, and Clostridium sporogenes species were chosen for their redox enzyme systems and evaluated for their ability to induce polymer formation. Parameters including cell and catalyst concentration, initiator species, and monomer type were investigated. Water-soluble synthetic polymers were produced in the presence of the bacteria with full preservation of cell viability. This method provides a means by which bacterial redox systems can be exploited to generate “unnatural” polymers in the presence of “host” cells, thus setting up the possibility of making natural–synthetic hybrid structures and conjugates.     

Preconcentration of trace amounts of manganese from natural waters by means of a macroreticular poly(dithiocarbamate) resin

A chelating poly(dithiocarbamate) resin (PDTC) with macroreticular support is characterized as effective collector for traces of manganese from natural waters. Using small PDTC columns preconcentration of manganese can be achieved even at high flow-rates (5-6 ml/min) and sample volumes (1500 ml). Accordingly, PDTC resin is used for the preconcentration of manganese from water samples prior to its determination by flame atomic-absorption spectrometry. A series of ions abundant in natural waters do not interfere. The sensitivity and detection limit were 2.5 and 0.5 mug/l., respectively. The relative standard deviations of the results for a manganese concentration of 40-400 mug/l. are in the range 1.1-6.2%. In mineral and tap waters analysed, the manganese concentration range was between 2.9 and 30.8 mug/l.     

Polymerisation de monomeres a structures biologiques

Fixation of biological compounds (cholesterol and testosterone) on (2-hydroxyethyl)methacrylate has been realized by a carbonate linkage. These new monomers have been characterized by N.M.R. and i.r.; they have been polymerized by a radical process. Resulting homopolymers have been analysed and compared with polymers bearing similar active compounds, previously synthesized by chemical modification of poly (2-hydroxyethyl)methacrylate.     

Fluorinated hydroxytelechelic polybutadiene as additive in cationic photopolymerization of an epoxy resin

Fluorinated hydroxytelechelic polybutadiene (PBF), which is synthesized from the radical addition of a fluorinated mercaptan onto a hydroxytelechelic polybutadiene was used as an efficient surface and mechanical modifier in original formulations to enable the UV cationic polymerization of a telechelic diepoxy cycloaliphatic oligomer, leading to crosslinked polymers. Various amounts of PBF were used (ranging between 0 and 15 wt %). The kinetics of photocrosslinking revealed that the diepoxyde conversion reached 70% only in the absence of PBF, whereas it was about 90% in the presence of 10 wt % of PBF. When the PBF content increased, the dynamic mechanical measurements showed that: (i) the glass transition temperature values decreased and (ii) the resilience increased. The hydrophobicity of these polymers was investigated from the water contact angle (WCA) values showing a surface modification of the epoxy‐based system. Indeed, great modifications were noted on the extreme surface (i.e., air side) of the polymers (with WCA values as high as 120°) in contrast to those observed on the substrate side. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2835–2842, 2009     

Cyanide ion complexation by a cationic borane

While we have previously reported that [1-(Mes2B)-8-(Me3NCH2)-C10H6]+ ([2]+) complexes fluoride ions to form [1-(Mes2FB)-8-(Me3NCH2)-C10H6] (2-F), we now show that this cationic borane also complexes cyanide to form [1-(Mes2(NC)B)-8-(Me3NCH2)-C10H6] (2-CN). This reaction also occurs under biphasic conditions (H2O-CHCl3) and may serve to transport cyanide in organic phases. The zwitterionic cyanoborate 2-CN has been fully characterized and its crystal structure determined. UV-vis titration experiments carried out in THF indicate that [2]+ has a higher affinity for fluoride (K > 10(8) M(-1)) than cyanide (K = 8.0 (+/-0.5) x 10(5) M(-1)). Steric effects which impede cyanide binding to the sterically congested boron center of [2]+ are most likely at the origin of this selectivity. Finally, electrochemical studies indicate that [2]+ is significantly more electrophilic than its neutral precursor 1-(Mes2B)-8-(Me2NCH2)-(C10H6) (1). These studies also show that reduction of [2]+ is irreversible, possibly because of elimination of the NMe3 moiety under reductive conditions. In fact, [2]OTf reacts with NaBH4 to afford 1-(Mes2B)-8-(CH3)-(C10H6) (4) which has also been fully characterized.     

Influence of the initiating mechanism on the cationic photopolymerization of a cycloaliphatic epoxy resin with arylsulfonium salts

The photocuring process of widely used 3,4‐epoxycyclohexylmethyl 3′,4′‐epoxycyclohexane carboxylate has been investigated with differential scanning photocalorimetry and attenuated total reflection/Fourier transform infrared. Mixed salts of triarylsulfonium hexafluoroantimonate have been employed as the photoinitiator. The photocuring of the biscycloaliphatic resins exhibits a complex behavior: the overall heat of reaction (including dynamic thermal postcuring) depends on the photocuring temperature, surprisingly high reaction rates are observed at lower photocuring temperatures, and the range of the glass transition of the fully cured material broadens and shifts to higher temperatures as the photocuring temperature increases. It is assumed that the balance between the initiation step and the propagation step is responsible for the changes in the reaction mechanism that produce the observed experimental results. This balance may depend on the amount of the photoinitiator, the irradiation intensity, and the photocuring temperature. The structure and final properties of the material may therefore depend on the adjustment of these parameters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 16–25, 2007