Ion-pair structure of vaporized ionic liquid studied by matrix-isolation FTIR spectroscopy with DFT calculations: a case of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate

The matrix-isolation infrared spectrum of a thermally evaporated ionic liquid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([Emim][OTf]), was measured by FTIR spectroscopy and analyzed with the aid of DFT calculations. The main chemical species in the observed IR spectrum was mainly identified as the 1:1 cation-anion pair, which corresponds to the second stable ion-pair structure bonded through five hydrogen bonds between three O atoms of the anion side and four H atoms of the cation.     

Diastereoselective protonation on a radical anion in the photoallylation and photoreduction of 1,1-dicyano-2-methyl-3-phenyl-1-butene by allyltrimethylsilane

Diastereoselectivity in the photoallylation and photoreduction of 1,1-dicyano-2-methyl-3-phenyl-1-butene by allyltrimethylsilane in the presence of phenanthrene was dependent on the structures and stoichiometry of the added carboxylic acids. Diastereoselectivity increased up to 72% by the addition of equimolar amount of l-lactic acid based on the alkene.     

Behavior of a polymer chain immersed in a binary mixture of solvents

The behavior of a polymer chain immersed in a binary solvent mixture is investigated via a single-polymer simulation using an effective Hamiltonian, where the solvent effects are taken into account through a density-functional theory for polymer-solvent admixtures. The liquid-liquid phase separation of the binary solvent mixture is modeled as that of a Lennard-Jones binary fluid mixture with weakly attractive interactions between the different components. Two types of energetic preferences of the polymer chain for the better solvent-(A) no preferential solvophilicity and (B) strong preferential solvophilicity-are employed as polymer-solvent interaction models. The radius of gyration and the polymer-solvent radial distribution functions are determined from the simulations of various molar fractions along an isotherm slightly above the critical temperature of the liquid-liquid phase separation. These quantities near the critical point conspicuously depend on the strength of the preferential solvophilicity. In the case where the polymer exhibits a strong preferential solvophilicity, a remarkable expansion of the polymer chain is observed near the critical point. On the other hand, in the case where the polymer has no preferential solvophilicity, no characteristic variation of the polymer conformation is observed even near the critical point. These results indicate that the expansion of a polymer chain enhances the local phase separation around it, acting as a nucleus of demixing in the vicinity of the critical point. This phenomenon in binary solvents near the liquid-liquid critical point is similar to the expansion of the polymer chain in one-component supercritical solvents near the liquid-vapor critical point, which we have reported [T. Sumi and H. Sekino J. Chem. Phys. 122, 194910 (2005)].     

Characterization of chemiluminescence from singlet oxygen under laminar flow conditions in a micro-channel and its quenching with beverages

Singlet oxygen was generated by reaction of sodium hypochlorite and hydrogen peroxide in a micro-channel. The two reagent solutions were delivered into the micro-channel by a syringe pump, providing a laminar flow liquid-liquid interface. The chemiluminescence from the singlet oxygen was emitted in the collapse of the interface due to molecular diffusion under laminar flow conditions. The chemiluminescence intensity was observed continuously and stably for each combination of reagents fed into the micro-channel; while, in the normal batch-type reactor the chemiluminescence peaks from singlet oxygen were observed within ca. 5 s. The features of the chemiluminescence emitted under laminar flow conditions were examined by changing the concentrations of sodium hypochlorite and hydrogen peroxide; the concentrations of 2.5 mM sodium hypochlorite and 7.5 mM hydrogen peroxide provided highest chemiluminescence intensities without bubble formation. Also, the effects of beverages, such as green tea, coffee, white wine, red wine, and sake (rice wine), on the chemiluminescence intensity as well as the concentrations of sodium hypochlorite and hydrogen peroxide were examined. The chemiluminescence intensities observed with addition of the beverages to the reagents decreased in the following orders; green tea > coffee > red wine > rice wine > white wine (being added to sodium hypochlorite); coffee > white wine > green tea > red wine > rice wine (being added to hydrogen peroxide). It was found that coffee decreased the chemiluminescence intensity (ca. 33% chemiluminescence decrease) without altering the concentrations of sodium hypochlorite or hydrogen peroxide. The cause of the decrease in chemiluminescence with coffee is discussed.     

Modification of Wide‐Band‐Gap Oxide Semiconductors with Cobalt Hydroxide Nanoclusters for Visible‐Light Water Oxidation

Cobalt‐based compounds, such as cobalt(II) hydroxide, are known to be good catalysts for water oxidation. Herein, we report that such cobalt species can also activate wide‐band‐gap semiconductors towards visible‐light water oxidation. Rutile TiO₂ powder, a well‐known wide‐band‐gap semiconductor, was capable of harvesting visible light with wavelengths of up to 850 nm, and thus catalyzed water oxidation to produce molecular oxygen, when decorated with cobalt(II) hydroxide nanoclusters. To the best of our knowledge, this system constitutes the first example that a particulate photocatalytic material that is capable of water oxidation upon excitation by visible light can also operate at such long wavelengths, even when it is based on earth‐abundant elements only.     

Infrared spectroscopy of ozone-water complex in a neon matrix

Matrix isolation infrared spectroscopy has been applied to study an ozone-water complex of atmospheric interest. The complex was identified in the spectral region of three normal modes of ozone and water. Ab initio calculation at MP4(SDQ), QCISD, and CCSD(T) levels indicates the existence of only one stable conformer, which accords with the present experimental result. This conformer belongs to the Cs symmetry group where two molecular planes of ozone and water are perpendicular to the Cs symmetry plane. The binding energy was calculated to be 1.89 kcal/mol at the CCSD(T)/6-311++G(3df,3pd)//CCSD(T)/6-311++G(d,p) level of theory. The formation constant and atmospheric abundance of the ozone-water complex are estimated using the thermodynamic and spectroscopic data obtained.     

Kinetic study on disproportionations of C1 aldehydes in supercritical water: methanol from formaldehyde and formic acid

The reaction pathways and kinetics of C1 aldehydes, formaldehyde (HCHO) and formic acid (HCOOH=HOCHO), are studied at 400 degrees C in neat condition and in supercritical water over a wide range of water density, 0.1-0.6 g/cm3. Formaldehyde exhibits four reactions: (i) the self-disproportionation of formaldehyde generating methanol and formic acid, (ii) the cross-disproportionation between formaldehyde and formic acid generating methanol and carbon dioxide, (iii) the water-independent self-disproportionation of formaldehyde generating methanol and carbon monoxide, and (iv) the decarbonylation of formaldehyde generating hydrogen and carbon monoxide. The self- and cross-disproportionations overwhelm the water-independent self-disproportionation and the formaldehyde decarbonylation. The rate constants of the self- and cross-disproportionations are determined in the water density range of 0.1-0.6 g/cm3. The rate constant of the cross-disproportionation is 2-3 orders of magnitude larger than that of the self-disproportionation, which indicates that formic acid is a stronger reductant than formaldehyde. Combining the kinetic results with our former computational study on the equilibrium constants of the self- and cross-disproportionations, the reaction mechanisms of these disproportionations are discussed within the framework of transition-state theory. The reaction path for methanol production can be controlled by tuning the water density and reactant concentrations. The methanol yield of approximately 80% is achieved by mixing formaldehyde with formic acid in the ratio of 1:2 at the water density of 0.4 g/cm3.     

Total synthesis of borrelidin

The total synthesis of borrelidin has been achieved. The best feature of our synthetic route is macrocyclization at C11-C12 for the construction of an 18-membered ring after esterification between two segments. A detailed examination of the macrocyclization led us to the samarium(II) iodide-mediated intramolecular Reformatsky-type reaction as the most efficient synthetic approach. The two key segments were synthesized through regioselective methylation, directed hydrogenation, stereoselective Reformatsky-type reaction, and MgBr2.Et2O-mediated chelation-controlled allylation.     

Microfluidic flow control on charged phospholipid polymer interface

A type of charged phospholipid polymer biointerface was constructed on a quartz microfluidic chip to control the electroosmotic flow (EOF) and to suppress non-specific protein adsorption through one-step modification. A negatively charged phospholipid copolymer containing 2-methacryloyloxyethyl phosphorylcholine (MPC), n-butyl methacrylate (BMA), potassium 3-methacryloyloxypropyl sulfonate (PMPS) and 3-methacryloxypropyl trimethoxysilane (MPTMSi) moieties (referred to as PMBSSi) was synthesized to introduce such phosphorylcholine segments as well as surface charges onto the silica-based microchannels via chemical bonding. At neutral pH, the homogenous microchannel surface modified with 0.3 wt% PMBSSi in alcoholic solution, retained a significant cathodic EOF ((1.0 +/- 0.1) x 10(-4) cm(2) V(-1) s(-1)) with approximately one-half of the EOF of the unmodified microchannel ((1.9 +/- 0.1) x 10(-4) cm(2) V(-1) s(-1)). Along with another non-charged copolymer (poly(MPC-co-MPTMSi), PMSi), the regulation of the surface charge density can be realized by adjusting the concentration of PMBSSi or PMSi initial solutions for modification. Coincidently, the zeta-potential and the EOF mobility at neutral pH showed a monotonically descending trend with the decrease in the charge densities on the surfaces. This provides a simple but feasible approach to controlling the EOF, especially with regard to satisfying the requisites of miniaturized systems for biological applications requiring neutral buffer conditions. In addition, the EOF in microchannels modified with PMBSSi and PMSi could maintain stability for a long time at neutral pH. In contrast to the EOF in the unmodified microchannel, the EOF in the modified microchannel was only slightly affected by the change in pH (from 1 to 10). Most importantly, although PMBSSi possesses negative charges, the non-specific adsorptions of both anionic and cationic proteins (considering albumin and cytochrome c, respectively, as examples) were effectively suppressed to a level of 0.15 microg cm(-2) and lesser in the case of the 0.3 wt% PMBSSi modification. Consequently, the variation in the EOF mobility resulting from the protein adsorption was also suppressed simultaneously. To facilitate easy EOF control with compatibility to biomolecules delivered in the microfluidic devices, the charged interface described could provide a promising option.