Photocatalytic Hydrogenation of Alkenes Using Water as Both the Reductant and the Proton Source.

Utilization of clean and low-cost water as the reductant to enable hydrogenation of alkenes is highly attractive in green chemistry. However, this research subject is considerably challenging due to the sluggish kinetics of the water oxidation half-reaction. It is also very difficult to avoid the undesired oxidation of alkenes because that this oxidation is far easier to occur than the desired oxidation of water from thermodynamic standpoint. Herein, this challenge is overcome by applying a cooperative catalysis where HCl is used as the cocatalyst to accelerate Pt/g-C3N4-catalyzed water oxidation and suppress the undesired oxidation of the alkene. This provides an example for using water as the reductant and the proton source to enable the photocatalytic hydrogenation of alkenes. The present method exhibits broad substrate applicability, and allows various arylethenes and aliphatic alkenes to undergo the hydrogenation smoothly.

Coupling photocatalytic water oxidation with reductive transformations of organic molecules.

The utilization of readily available and non-toxic water by photocatalytic water splitting is highly attractive in green chemistry. Herein we report that light-induced oxidative half-reaction of water splitting is effectively coupled with reduction of organic compounds, which provides a light-induced avenue to use water as an electron donor to enable reductive transformations of organic substances. The present strategy allows various aryl bromides to undergo smoothly the reductive coupling with Pd/g-C3N4* as the photocatalyst, giving a pollutive reductant-free method for synthesizing biaryl skeletons. Moreover, the use of green visible-light energy endows this process with more advantages including mild conditions and good functional group tolerance. Although this method has some disadvantages such as a use of environmentally unfriendly 1,2-dioxane, an addition of Na2CO3 and so on, it can guide chemists to use water as a reducing agent to develop clean procedures for various organic reactions.

Cu2 O-Catalyzed Conversion of Benzyl Alcohols Into Aromatic Nitriles via the Complete Cleavage of the C≡N Triple Bond in the Cyanide Anion.

Nitrogen transfer from cyanide anion to an aldehyde is emerging as a promising method for the synthesis of aromatic nitriles. However, this method still suffers from a disadvantage that a use of stoichiometric Cu(II) or Cu(I) salts is required to enable the reaction. As we report herein, we overcame this drawback and developed a catalytic method for nitrogen transfer from cyanide anion to an alcohol via the complete cleavage of the C≡N triple bond using phen/Cu2 O as the catalyst. The present condition allowed a series of benzyl alcohols to be smoothly converted into aromatic nitriles in moderate to high yields. In addition, the present method could be extended to the conversion of cinnamic alcohol to 3-phenylacrylonitrile.

Density Functional Study of Trimetallic AuxPdyPtz (x + y + z = 7) Clusters and Their Interactions with the O2 Molecule.

Density functional theory calculations were performed to investigate the structural and energetic properties of trimetallic AuxPdyPtz clusters with x + y + z = 7. The possible stable geometrical configurations with their electronic states are determined. We analyze the chemical order, binding energies, vertical ionization potential, electron affinity, and HOMO-LUMO gaps as a function of the whole concentration range. The affinity of AuxPdyPtz clusters toward one O2 molecule is also evaluated in terms of the changes in geometry, adsorption energy, and charge transfer.

A theoretical investigation of the interactions between hydroxyl-functionalized ionic liquid and water/methanol/dimethyl sulfoxide.

Density functional calculations have been used to investigate the interactions of 1-(2-hydroxyethyl)-3-methylimidazolium ([C2OHmim](+))-based ionic liquids (hydroxyl ILs) with water (H2O), methanol (CH3OH), and dimethyl sulfoxide (DMSO). It was found that the cosolvent molecules interact with the anion and cation of each ionic liquid through different atoms, i.e., H and O atoms, respectively. The interactions between the cosolvent molecules and 1-ethyl-3-methylimizolium ([C2mim](+))-based ionic liquids (nonhydroxyl ILs) were also studied for comparison. In the cosolvent-[nonhydroxyl ILs] systems, a furcated H-bond was formed between the O atom of the cosolvent molecule and the C2-H and C6-H, while there were always H-bonds involving the OH group of the cation in the cosolvent-[hydroxyl ILs] systems. Introducing an OH group on the ethyl side of the imidazolium ring may change the order of solubility of the molecular liquids.

Density functional study of molecular nitrogen adsorption on gold-copper and gold-silver binary clusters.

Density functional theory calculations were performed to investigate the adsorption behaviors of nitrogen molecule on small bimetallic AunCum and AunAgm clusters, with n + m ≤ 5. In all cases the N2 forms a linear or quasi-linear M-N-N structure (M = Au, Cu or Ag). The adsorption energies of N2 on pure metal clusters follow the order CunN2 > AunN2 > AgnN2, which is due to the weaker orbital interaction between silver and N2. N2 prefers to bind to a copper atom in AunCumN2 complexes and prefers to bind to a silver atom in AunAgmN2 complexes. The combination of Cu atoms into Aun clusters makes the cluster more reactive toward N2 while the combination of Ag atoms into Aun clusters makes the cluster less reactive toward N2. The electrostatic interaction is strengthened while the back-donation from metal to N2 is reduced in bimetallic cluster nitrides, as compared to the mono cluster nitrides. The N-N stretching frequencies are all red-shifted upon adsorption and the M-N stretching frequencies are highly correlated to the atoms to which the N is attached.

Quantitative counting of single fluorescent molecules by combined electrochemical adsorption accumulation and total internal reflection fluorescence microscopy.

We developed an ultrasensitive quantitative single-molecule imaging method for fluorescent molecules using a combination of electrochemical adsorption accumulation and total internal reflection fluorescence microscopy (TIRFM). We chose rhodamine 6G (R6G, fluorescence dye) or goat anti-rat IgG(H+L) (IgG(H+L)-488), a protein labeled by Alexa Fluor 488 or DNA labeled by 6- CR6G (DNA-R6G) as the model molecules. The fluorescent molecules were accumulated on a light transparent indium tin oxide (ITO) conductive microscope coverslip using electrochemical adsorption in a stirred solution. Then, images of the fluorescent molecules accumulated on the ITO coverslip sized 40 x 40 microm were acquired using an objective-type TIRFM instrument coupled with a high-sensitivity electron multiplying charge-coupled device. One hundred images of the fluorescent molecules accumulated on the coverslip were taken consecutively, one by one, by moving the coverslip with the aid of a three-dimensional positioner. Finally, we counted the number of fluorescent spots corresponding to single fluorescent molecules on the images. The linear relationships between the number of fluorescent molecules and the concentration were obtained in the range of 5 x 10(-15) to 5 x 10(-12) mol/L for R6G, 3 x 10(-15) to 2 x 10(-12) mol/L for IgG(H+L)-488, and 3 x 10(-15) to 2 x 10(-12) mol/L for DNA-R6G.