Probing intermolecular couplings in liquid water with two-dimensional infrared photon echo spectroscopy

Two-dimensional infrared photon echo and pump probe studies of the OH stretch vibration provide a sensitive probe of the correlations and couplings in the hydrogen bond network of liquid water. The nonlinear response is simulated using numerical integration of the Schrodinger equation with a Hamiltonian constructed to explicitly treat intermolecular coupling and nonadiabatic effects in the highly disordered singly and doubly excited vibrational exciton manifolds. The simulated two-dimensional spectra are in close agreement with our recent experimental results. The high sensitivity of the OH stretch vibration to the bath dynamics is found to arise from intramolecular mixing between states in the two-dimensional anharmonic OH stretch potential. Surprisingly small intermolecular couplings reproduce the experimentally observed intermolecular energy transfer times.     

Synthesis, photophysical and electrochemical properties of perfluoroisopropyl substituted binuclear phthalocyanine conjugated with a butadiyne linker

Synthesis of 1,3-butadiyne-bridged perfluoroisopropyl binuclear phthalocyanine 2 has been successfully achieved from unsymmetrical A₃B-type iodo-perfluoroisopropyl phthalocyanine by palladium-catalyzed cross-coupling with trimethylsilylacetylene and copper-catalyzed Glaser homo-coupling as key reactions. The dyad 2 essentially remains non-aggregated irrespective of solvent and concentration. Electrochemical analysis suggests oxidation is not possible whereas the molecule is more easily reduced. All the results are advantages for photodynamic therapy (PDT).     

Simultaneous determination of tetrahydro-β-carbolines and β-carbolines

Summary Reversed-phase ion-pair HPLC with fluorimetric detectors connected in series was studied for the simultaneous determination of two tetrahydro--carbolines and two -carbolines. After additon of internal standards the samples were reacted with fluorescamine, and then subjected to serial extractions to remove their precursor (tryptamine) from the analytical system. This treatment not only suppressed the artefactual formation of tetrahydro--carbolines and -carbolines during analysis, but also effectively purified them. Under optimum conditions, using trifluoroacetic acid as counter ion, all analytes were separated within 14 min and without major interfering peaks. The quantitative ranges were 0.25–80.0 ng mL^–1 for both tetrahydro--carbolines and 0.1–30.0 ng mL^–1 for both -carbolines. Replicate spiking experiments showed that recovery from most of the samples tested was over 90% and the relative standard deviation ranged from 0.7 to 10.4% within and between assays. The proposed method was applicable to various materials such as soy sauce, vinegar, ketchup, tabasco, beer, wine, sake, whisky, brandy, cows' milk, coffee, cocoa, cheese, cigarette smoke and urine.     

Plasma Copolymerization of Pyrrole with Si-Compounds

The plasma copolymerization of pyrrole with hexamethyldisiloxane, hexamethyldisilane and hexamethyldisilazane was investigated with regard to the polymer deposition characteristics and the properties of the product films. Deposition rates were evaluated by monitoring the weight increase of the deposits over time, and the effect of varying the experimental set up parameters was determined. The results of deposition rates and quantitative IR analysis suggested that the increasing amounts of Si-components were incorporated into the polymer matrix as the supply ratio of the Si-monomer was increased. The Si-component in the copolymer brought some dramatic effects on the physical properties of the films and changed the hydrophobicity of the surfaces, as reflected in the advancing and receding contact angle measurements. The experimental results obtained are discussed in terms of the contribution of the polar and dispersion components of surface energy.     

Dielectric properties of glycerol/water mixtures at temperatures between 10 and 50 degrees C

At six temperatures T between 10 and 50 degrees C and at mole fractions x(g) of glycerol (0相似文献   

Rhodium-catalyzed allyl transfer from homoallyl alcohols to aldehydes via retro-allylation followed by isomerization into ketones

Retro-allylation of homoallyl alcohol by rhodium catalysis occurs to generate allylrhodium species. This allylrhodium reacts with aldehydes to give the corresponding secondary alcohols in situ. Isomerization of these alcohols proceeds in the same pots to furnish the corresponding saturated ketones in good yields. [reaction: see text]     

Efficient approach to 1,2-diazepines via formal diazomethylene insertion into the C-C bond of cyclobutenones

Efficient monocyclic 1,2-diazepine formation via a tandem electrocyclization reaction of cyclobutenones with lithiodiazoacetate is demonstrated. The reaction proceeds through an oxy anion-accelerated 4π-ring opening of cyclobutene followed by an 8π-ring closure of the resultant oxy anion-substituted diazo-diene under mild conditions to furnish a 1,2-diazepine via formal diazomethylene insertion into the C-C bond of cyclobutenone.     

Construction of carbocyclic ring of indoles using ruthenium-catalyzed ring-closing olefin metathesis

The selective synthesis of substituted indoles was achieved by the ring-closing olefin metathesis (RCM)/elimination sequence or the RCM/tautomerization sequence of functionalized pyrrole precursors. The RCM/elimination sequence was also applied to double ring closure to yield a substituted carbazole.     

Stable Potential Windows for Long‐Term Electrocatalysis by Manganese Oxides Under Acidic Conditions

Efficient, earth‐abundant, and acid‐stable catalysts for the oxygen evolution reaction (OER) are missing pieces for the production of hydrogen via water electrolysis. Here, we report how the limitations on the stability of 3d‐metal materials can be overcome by the spectroscopic identification of stable potential windows in which the OER can be catalyzed efficiently while simultaneously suppressing deactivation pathways. We demonstrate the benefits of this approach using gamma manganese oxide (γ‐MnO₂), which shows no signs of deactivation even after 8000 h of electrolysis at a pH of 2. This stability is vastly superior to existing acid‐stable 3d‐metal OER catalysts, but cannot be realized if there is a deviation as small as 50‐mV from the stable potential window. A stable voltage efficiency of over 70 % in a polymer–electrolyte membrane (PEM) electrolyzer further verifies the availability of this approach and showcases how materials previously perceived to be unstable may have potential application for water electrolysis in an acidic environment.