Selective semihydrogenation of alkynes with the Mn(I) alkyl catalyst fac-[Mn(dippe)(CO)3(CH2CH2CH3)] (dippe = 1,2-bis(di-iso-propylphosphino)ethane) as a precatalyst is described. The required hydrogen gas is either directly employed or in situ-generated upon alcoholysis of KBH4 with methanol. A series of aryl-aryl, aryl-alkyl, alkyl-alkyl, and terminal alkynes was readily hydrogenated to yield E-alkenes in good to excellent isolated yields. The reaction proceeds at 60 °C for directly employed hydrogen or at 60-90 °C with in situ-generated hydrogen and catalyst loadings of 0.5-2 mol %. The implemented protocol tolerates a variety of electron-donating and electron-withdrawing functional groups, including halides, phenols, nitriles, unprotected amines, and heterocycles. The reaction can be upscaled to the gram scale. Mechanistic investigations, including deuterium-labeling studies and density functional theory (DFT) calculations, were undertaken to provide a reasonable reaction mechanism, showing that initially formed Z-isomer undergoes fast isomerization to afford the thermodynamically more stable E-isomer.

The selective semihydrogenation of alkynes with the Mn(I) alkyl catalyst fac-[Mn(dippe)(CO)3(CH2CH2CH3)] (dippe = 1,2-bis(di-iso-propylphosphino)ethane) as pre-catalyst is described. Hydrogen gas required for the hydrogenation is generated in situ upon alcoholysis of KBH4 with methanol. A series of aryl-aryl, aryl-alkyl, alkyl-alkyl and terminal alkynes were readily hydrogenated to yield E-alkenes in good to excellent isolated yields. The reaction proceeds at 90°C with catalyst loadings of 0.5 -2 mol%. The implemented protocol tolerates a variety of electron donating and electron withdrawing functional groups including halides, phenols, nitriles, unprotected amines and heterocycles. The reaction can be upscaled to the gram scale. Mechanistic investigations including deuterium labelling studies and DFT calculations were undertaken to provide a reasonable reaction mechanism showing that initially formed Z-isomer undergoes fast isomerization to afford the thermodynamically more stable E-isomer.

The catalytic hydrogenation of different aldehydes to the corresponding alcohols was investigated using an FeII hydride pincer complex as catalyst in the supported ionic liquid phase (SILP) reaction mode. Two different ionic liquids of the type [X4441][NTf2] with X=N or P were applied with mesoporous silica gel as support, which was coated first with a chemisorbed monolayer of the corresponding modified IL to remove acidic surface OH‐groups and to prevent IL leaching. Quantitative conversion with turn‐over frequencies in the order of 1000 h– 1 were obtained for various aromatic and heteroaromatic aldehydes and highly selective aldehyde reduction was observed also for substrates containing reducible C=C bonds. Aldehydes with longer aliphatic chains or cycloalkyl substituents, however, showed no conversion here, in contrast to a previous study with an imidazolium‐based ionic liquid. These differences were ascribed primarily to differences in substrate/ionic liquid interactions. Whereas [N4441][NTf2] and [P4441][NTf2] gave essentially identical results for different substrates in single‐batch reactions, prolonged use of the catalyst in repeated reaction cycles lead to a quick drop‐off in catalyst activity in [P4441][NTf2], but a continuous, quantitative conversion in [N4441][NTf2].

Dialkynes are grafted onto hydrogen‐passivated silicon wafers, porous silicon, and silicon nanowires via thermally induced hydrosilylation followed by surface functionalization via azide alkyne cycloaddition. The surfaces are characterized with Fourier transform infrared spectroscopy (FTIR) and electrochemical measurements that indicate a correlation between the quality of the organic layer and the morphology of the substrate. After the initial hydrosilylation reaction, the amount of accessible surface bonded alkynes is observed to be substantially lower on porous, irregular surfaces compared to flat wafers and well‐defined vertically aligned silicon nanowire arrays, thus precluding an effective subsequent azide‐alkyne cycloaddition on porous silicon.

We present the use of silica-supported ionic liquids as catalysts for the continuous production of propylene carbonate from propylene oxide using supercritical carbon dioxide as solvent and reagent. Considerable differences in the catalytic activity of ionic liquids in homogeneous catalysis in batch mode and in continuous-flow using supported species processes were found, suggesting that a synergistic effect between ionic liquid and silica support material takes place. While supported ionic liquids prepared via physisorption of [C(2)mim]Br showed the highest catalytic activity, studies on long-term stability showed a rapid loss in yield due to the formation of undesired polypropylene carbonate that agglomerated in the ionic liquid layer. Improved long-term stability was found for ionic liquids covalently bound to the silica support materials, suggesting that a compromise between activity and stability is the best solution for the continuous production of propylene carbonate.

The synthesis and characterization of dicarbonyl Fe(II) PNP pincer complexes of the type cis-[Fe(PNP-iPr)(CO)2(X)]+ (X = Br, Cl) is described. These complexes are slowly formed when solutions of complexes trans-[Fe(PNP-iPr)(CO)2(X)]+ are kept in the dark for 9 h (X = Br) and 3 days (X = Cl). Upon exposure to visible light these complexes isomerize to the respective trans-dicarbonyl complexes within a few hours. The visible-light reaction seems to involve reversible CO dissociation. The isomerization can be repeated serval times. A mechanistic rationale for this isomerization process is established by means of DFT calculations.

In this work, the supported ionic liquid phase (SILP) method was applied for the immobilization of a newly developed, well-defined hydride Fe(ii) PNP pincer complex dissolved an in ionic liquid (IL) onto polymer-based spherical activated carbon.

A base-tolerant supported ionic-liquid-phase (SILP) system containing a well-defined hydride Fe(II) PNP pincer complex has been prepared, structurally characterized, and used as catalyst in the hydrogenation of aldehydes to alcohols. The new SILP catalyst, with the optimum pore filling, was highly active exhibiting TONs and TOFs of up to 1000 and 4000 h(-1), respectively, under mild conditions (25 degrees C, 10-50 bar H-2 pressure) without significant leaching of both the complex and the IL.

Infrared spectroscopy is an instrumentally simple, versatile surface analytical technique, which yields highly specific information about the composition and structure of adsorbates and thin films on solid surfaces in contact with gaseous or liquid ambient media. A range of different surface-sensitive techniques is available today, which probe flat, low surface area samples or powdered high surface area samples by measuring the radiation either transmitted, reflected or emitted by the sample. This article focuses on external reflection infrared spectroscopy, where infrared radiation reflected from a flat sample in the specular direction is analyzed. The experimental setup and the instrumental components of external reflection infrared measurements are described and the parameters for optimizing the sensitivity are discussed. Some representative examples of infrared reflection spectra of adsorbates or thin films on metal and nonmetal substrates are shown and the chemical and structural information contained therein is analyzed. In situ studies of a liquid film deposition and growth process and of an electrochemical reaction monitored at the electrode/electrolyte interface are presented and some recent surface-enhanced infrared measurements with record-setting detection limits are introduced.

In photopolymerization reactions, mostly multifunctional monomers are employed, as they ensure fast reaction times and good final mechanical properties of the cured materials. Drawing conclusions about the influence of the components and curing conditions on the mechanical properties of the subsequently formed insoluble networks is challenging. Therefore, an in situ observation of chemical and mechanical characteristics during the photopolymerization reaction is desired. By coupling of an infrared spectrometer with a photorheometer, a broad spectrum of different photopolymerizable formulations can be analyzed during the curing reaction. The rheological information (i.e., time to gelation, final modulus, shrinkage force) can be derived from a parallel plate rheometer equipped with a UV- and IR-translucent window (glass for NIR and CaF2 window for MIR). Chemical information (i.e., conversion at the gel point and final conversion) is gained by monitoring the decrease of the corresponding IR-peak for the reactive monomer unit (e.g., C═C double bond peak for (meth)acrylates, H-S thiol and C═C double bond peak in thiol-ene systems, C-O epoxy peak for epoxy resins). Depending on the relative concentration of reactive functional groups in the sample volume and the intensity of the IR signal, the conversion can be monitored in the near-infrared region (e.g., acrylate double bonds, epoxy groups) or the MIR region (e.g., thiol signal). Moreover, an integrated Peltier element and external heating hood enable the characterization of photopolymerization reactions at elevated temperatures, which also widens the window of application to resins that are waxy or solid at ambient conditions. By switching from water to heavy water, the chemical conversion during photopolymerization of hydrogel precursor formulations can also be examined. Moreover, this device could also represent an analytical tool for a variety of thermally and redox initiated systems.

Liquid-repellent surfaces based on slippery liquid-infused porous substrates (SLIPS) were prepared from porous, nanostructured silicon surfaces with different surface functionalization, infused with the polar ionic liquid 1-ethyl-3-methylimidazolium methylsulfate ([C2mim]MeSO4). Contrary to nonpolar SLIPS based on perfluorinated substrates and infusion liquids, [C2mim]MeSO4 forms stable SLIPS with high energy surfaces like native silicon (Si–SiO2) or ionic liquid-functionalized silicon (Si-[C3mim]Cl), whose liquid-repellent properties against low surface tension liquids (toluene, cyclohexane) were demonstrated by very low sliding angles (α < 3°) and low contact angle hysteresis (Δθ < 10°). These polar, ionic liquid-based SLIPS present a promising, environmentally benign extension of liquid-infused substrates to natural, high-energy oxide surfaces.

Most of the knowledge about properties and reactions at surfaces and interfaces is derived from classical surface science studies, where well-defined (often single crystal) solid surfaces are investigated in an ultrahigh vacuum environment with a multitude of different surface analytical techniques. The majority of these methods are intrinsically restricted to vacuum conditions, because the mean free path length of the probing particles (electrons, ions, atoms, etc.) in condensed or ambient pressure gaseous phases is so small that propagation over macroscopic distances is prevented. This entry reviews the contribution of ellipsometry to present knowledge of solid–liquid interfaces and will also show some of its potential for novel applications.

Photo-curing has become increasingly popular in wood coating applications relative to thermally initiated processes due to increased curing rate with reduction in solvent and energy requirements. Stressing the last advantage, light emitting diodes (LEDs) utilize less energy and last longer than traditional Hg lamps and are commercially available now in wavelengths below 400 nm. Although photo-curing does have its advantages, an additional difficulty is encountered when this is performed in open-air since molecular oxygen inhibits radical polymerization. This leads to insufficiently cured films that remain tacky at the surface. Although nitrogen gas inerting can be highly successful in excluding oxygen, chemical additives are often preferable to the small and medium-sized enterprise (SME) end user. A variety of additives have been introduced over the last 30 years both in the scientific and patent literature. We have chosen to experimentally reinvestigate the applicability of some of these additives (hydrogen donors, functional monomers, reducing agents, CO2 producing agents, and singlet oxygen scavengers). applying them to a urethane acrylate base formulation. Curing was performed with LED irradiation and effectiveness assessed by FTIR in transmission mode. (C) 2014 Elsevier B.V. All rights reserved.

Monolayers of terminal alkynes with long hydrocarbon chains CnH2n+1C[CH (n = 10, 13, 16) were prepared on Si(100) substrates via thermally induced hydrosilylation and the surface orientation of the hydrocarbon chains was investigated by external reflection infrared spectroscopy. It was found that under rigorous exclusion of oxygen in the monolayer preparation process, all three compounds yield highly characteristic IR reflection spectra, consisting of upward-pointing v(CH2) absorptions and downward-pointing v(CH3) absorptions, indicative of a highly ordered anisotropic film structure. Via spectral simulations it was found that the methylene backbones (CH2)n in these films adopt a uniform, all-trans conformation with a tilt angle of about 30° toward the surface normal, whereas the chain termini are disordered and give an isotropic film surface composed of randomly oriented CH3 groups. Lower quality films, which are hardly distinguishable from highly ordered films by other methods, but have been shown to exhibit inferior electrical properties, are clearly identified in their infrared (IR) spectra as partly disordered structures. External reflection IR therefore proves to be an exceptionally sensitive tool to detect structural defects in these monolayers.

A two-step process based on copper-free click chemistry is described, by which the surface of silicon nanowires can be functionalized with specific organic substituents. A hydrogen-terminated nanowire surface is first primed with a monolayer of an α,ω-diyne and thereby turned into an alkyne-terminated, clickable platform, which is subsequently coupled with an overlayer of an organic azide carrying the desired terminal functionality. The reactive, electron-deficient character of the employed diyne enabled a quantitative coupling reaction at 50 °C without metal catalysis, which opens up a simple and versatile route for surface functionalization under mild conditions without any potentially harmful additives.

Eine neue Generation von Plastiktransistoren aus leichten, flexiblen organischen Materialien erfordert neue Fabrikationsmethoden auf Basis lösungschemischer Prozesse bei niedrigen Temperaturen, kombiniert mit einer präzisen Kontrolle der Bauteilabmessungen im nm‐Bereich. Ultradünne SiO‐Filme als Gate‐Dielektrika in diesen Transistoren wurden durch einen schichtweisen Abscheidungs‐/Oxidationsprozess aus Filmen einer Polymervorstufe hergestellt. magnified image

A new generation of plastic transistors consisting primarily of light and flexible organic materials requires new fabrication methods which combine low-temperature, solution-phase processing with precise control in the nanometer range over the component dimensions. Ultrathin silicon oxide films, which serve as gate dielectric layers in these transistors, were recently grown at room temperature from polymer precursor films by a novel layer-by-layer deposition/oxidation process.

The purpose of our study was to design a new class of acrylate-based monomers with an LTV-cleavable heteroatom bond, offering the possibility to initiate radical polymerization upon irradiation with LTV-light. A method to derive the double bond conversion from the ATR-IR spectra of the monomers and the cured polymers was employed, that enabled us to calculate the theoretical polymerization heats of the new monomers. Their photopolymerization properties were determined by Photo Differential Scanning Calorimetry. Surprisingly, some of these new compounds exhibited high photoinitiation activity, comparable to well-established Type II photoinitiator systems like benzophenone/triethanolamine. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 392-403, 2009

The sensitivities of infrared spectra of thin adsorbate layers measured in either transmission, internal reflection or external reflection can be greatly increased if a light incidence medium with a high refractive index such as an IR-transparent solid material is used. This increase in sensitivity is due to the strong enhancement of the perpendicular electric field in a thin layer of low refractive index sandwiched between two high refractive index materials. Based on model calculations of a hypothetical sample layer, the influence and optimization of experimental parameters such as incidence angle, sample layer thickness and optical contact between layers are investigated. Under optimized conditions, this enhancement can exceed a factor of 100 when compared to conventional surface IR techniques. In addition, the spectra of sandwiched sample layers are governed by a uniform surface selection rule, such that only the perpendicular vibrational components are enhanced, and they permit a straightforward, substrate-independent analysis of surface orientations. Experimental examples of monolayer spectra of long-chain hydrocarbon compounds adsorbed onto gold and silicon substrates and contacted with a germanium crystal used as the incidence medium demonstrate the simple experimental realization and unprecedented sensitivity of this sandwich technique, and they offer novel insights into the chemistry and structure of monolayers confined and compressed between two solid surfaces. Figure IR reflection spectrum of a monolayer of a fatty acid methyl ester sandwiched between silicon and germanium.