Synthesis of 2(1H)-pyrazinone phosphonates via an Arbuzov-type reaction

A simple and catalyst-free method for the synthesis of phosphonated 2(1H)-pyrazinones is described starting from 3,5-dichloropyrazinones. The method also works for 3-bromo- and 3-iodopyrazinones. Classical heating conditions as well as microwave-enhanced reaction conditions were tested.     

Difluoromethyltrialkylammonium salts--their expeditious synthesis from chlorodifluoromethane and tertiary amines in the presence of concentrated aqueous sodium hydroxide. The catalytic process

We found that difluorocarbene generated from chlorodifluoromethane with 50% aqueous sodium hydroxide reacts with lipophilic tertiary amines 1a-g giving difluoromethyltrialkylammonium chlorides 2a-g in high yields. Similarly, difluoromethyltrialkylammonium iodides 3h-l, nitrates 4h-k, or isothiocyanates 5i,j were synthesized from hydrophilic tertiary amines 1h-l and the corresponding sodium or potassium salts. The process is catalytic with respect to the base used.     

Reduction of cationic free-base <Emphasis Type="Italic">meso</Emphasis>-tris-<Emphasis Type="Italic">N</Emphasis>-methylpyridinium-4-yl porphyrins in positive mode electrospray ionization mass spectrometry

Reductions involving more than one electron with formation of the M⁺ and [M+2H]⁺ ions were observed for electrosprayed meso-tris(N-methylpyridinium-4-yl)porphyrin iodides, MI₃. These reductions were studied by using different solvents and flow rates. Formation of the [M+2H]⁺ ions occurred only for protic solvents and to a larger extent at lower flow rates. The type of the fourth substituent does not seem to affect the reduction processes. Formation of the two reduced species, M⁺ and [M+2H]⁺ ions, may occur through the participation of counter ion/solvent clusters. Reduction of multiply charged, non-metallated species with formation of [M+nH]⁺ ions (n>1) was not observed before in positive mode electrospray mass spectrometry.     

Gas-phase structure of a pi-allyl-palladium complex: efficient infrared spectroscopy in a 7 T Fourier transform mass spectrometer

The performance of infrared (IR) spectroscopy of gas-phase ions in a commercially available 7 T Fourier transform ion cyclotron resonance mass spectrometer has been characterized. A pi-allyl-palladium reactive intermediate, [(pi-allyl)Pd(P(C6H5)3)2]+, involved in the catalytic allylation of amine is studied. A solution of this transition metal complex is electrosprayed, and the IR multiple photon dissociation (IRMPD) spectrum of the mass-selected ions is recorded in two spectral ranges. The fingerprint spectrum (650-1550 cm(-1)) is recorded using the Orsay free-electron laser, and the dependence of the IRMPD efficiency on laser power and irradiation time is characterized. The DFT-calculated IR absorption spectrum of the [(pi-allyl)Pd(P(C6H5)3)2]+ complex shows good agreement with the experimental spectrum. The pi-interaction between the palladium and the allyl moiety is reflected by the assignment of the IRMPD bands, and the observed allylic CH2 wagging modes appear to form a sensitive probe for the pi-interaction strength in metal-pi-allyl complexes. This spectral assignment is further supported by the analysis of the different IRMPD photofragmentation patterns observed at different photon energies, which are found to result from wavelength-specific photofragmentations. Nine peaks are well-resolved in the experimental spectrum, for which the bandwidth (fwhm) is on the order of 15 cm(-1). Resonances with a calculated IR intensity of 5 km/mol or larger are shown to be amenable for IRMPD, indicating an excellent sensitivity of our new experimental setup. Finally, the IR spectrum has also been recorded in the CH stretching region (2950-3150 cm(-1)) using a tabletop IR optical parametric oscillator/amplifier (OPO/OPA) laser source.     

Experimental and computational studies of nuclear substituted 1,1'-dimethyl-2,2'-bipyridinium tetrafluoroborates

The synthesis and spectral properties of a new 2,2'-bipyridinium ion, 1,1'-dimethyl-4,4'-(dimethylamino)-2,2'-bipyridinium bis(tetrafluoroborate) are reported. Rotation of the dimethylamino group is slow at room temperature on the 400 MHz 1H and 100 MHz 13C NMR time scales. Complete line shape fit of the dynamically broadened NMR spectra was used to determine the activation barriers for this process. The first complete set of UV-vis spectra for a 2,2'-bipyridinium dication and its one- and two-electron reduced products was reported. TD-DFT calculations were used to help assign the origin of the long wavelength absorptions in these species. The effect of substituents on the energies and conformational potential energy surfaces of all three species were also examined using the B3LYP/6-31G(d) computational method.     

Importance of catalyst–photoabsorber interface design configuration on the performance of Mo-doped BiVO4 water splitting photoanodes

Photoelectrochemical water splitting is mostly impeded by the slow kinetics of the oxygen evolution reaction. The construction of photoanodes that appreciably enhance the efficiency of this process is of vital technological importance towards solar fuel synthesis. In this work, Mo-modified BiVO₄ (Mo:BiVO₄), a promising water splitting photoanode, was modified with various oxygen evolution catalysts in two distinct configurations, with the catalysts either deposited on the surface of Mo:BiVO₄ or embedded inside a Mo:BiVO₄ film. The investigated catalysts included monometallic, bimetallic, and trimetallic oxides with spinel and layered structures, and nickel boride (Ni_xB). In order to follow the influence of the incorporated catalysts and their respective properties, as well as the photoanode architecture on photoelectrochemical water oxidation, the fabricated photoanodes were characterised for their optical, morphological, and structural properties, photoelectrocatalytic activity with respect to evolved oxygen, and recombination rates of the photogenerated charge carriers. The architecture of the catalyst-modified Mo:BiVO₄ photoanode was found to play a more decisive role than the nature of the catalyst on the performance of the photoanode in photoelectrocatalytic water oxidation. Differences in the photoelectrocatalytic activity of the various catalyst-modified Mo:BiVO₄ photoanodes are attributed to the electronic structure of the materials revealed through differences in the Fermi energy levels. This work thus expands on the current knowledge towards the design of future practical photoanodes for photoelectrocatalytic water oxidation.

     

Facile one-step synthesis of Ru doped NiCoP nanoparticles as highly efficient electrocatalysts for oxygen evolution reaction

Transition metal phosphides (TMPs) as ever-evolving electrocatalytic materials have attracted increasing attention in water splitting reactions owing to their cost-effective, highly active and stable catalytic properties. This work presents a facile synthetic route to NiCoP nanoparticles with Ru dopants which function as highly efficient electrocatalysts for oxygen evolution reaction (OER) in alkaline media. The Ru dopants induced a high content of Ni and Co vacancies in NiCoP nanoparticles, and the more defective Ru doped NiCoP phase than undoped NiCoP ones led to a greater number of catalytically active sites and improved electrical conductivity after undergoing electrochemical activation. The Ru doped NiCoP catalyst exhibited high OER catalytic performance in alkaline media with a low overpotential of 281 mV at 10 mA cm⁻² and a Tafel slope of 42.7 mV dec⁻¹.     

Study of pyrolysis kinetic of green corn husk

In this paper, it was suggested the use of green corn husk, which is a biomass from agro-industry, as an alternative source of energy through its pyrolysis. Green corn husk characterization was done through immediate and elemental analysis of its components: cellulose, hemicelluloses, and lignin. It was also measured its higher calorific value. The pyrolysis study of green corn husk was done by the isoconversion and the Master plots method. Thermogravimetric plots were obtained at heating rates of 5, 10, 15, and 20 °C min^?1. The pyrolysis kinetics parameters were studied through the Flynn–Wall–Ozawa (FWO), Kissinger, and Friedman models. The Master plots method was used to determine the pyrolysis reaction order. The results of the reaction energy activation were found to be in the range 105.21–157.46 kJ mol^?1 by the FWO method, 150.50 kJ mol^?1 by the Kissinger method, and ranged 120.66–163.81 kJ mol^?1 by the Friedman method. The Master plots method showed a three-way-transport diffusional kinetics for the biomass de-volatilization process. The higher calorific value found for green corn husk was 16.14 MJ kg^?1. The simulation showed correlation between the experimental data and the proposed model for conversion values up to 0.8.

     

Eleutherococcus sessiliflorus Inhibits Receptor Activator of Nuclear Factor Kappa-B Ligand (RANKL)-Induced Osteoclast Differentiation and Prevents Ovariectomy (OVX)-Induced Bone Loss

The aim of this study was to evaluate the effects of root bark of Eleutherococcus sessiliflorus (ES) on osteoclast differentiation and function in vitro and in vivo. In vitro, we found that ES significantly inhibited the RANKL-induced formation of TRAP-positive multinucleated osteoclasts and osteoclastic bone resorption without cytotoxic effects. ES markedly downregulated the expression of nuclear factor of activated T cells cytoplasmic 1 (NFATc1); c-Fos; and osteoclast-related marker genes, such as TRAP, osteoclast-associated receptor (OSCAR), matrix metalloproteinase-9 (MMP-9), calcitonin receptor, cathepsin K, the 38 kDa d2 subunit of the vacuolar H⁺-transporting lysosomal ATPase (Atp6v0d2), dendritic cell-specific transmembrane protein (DC-STAMP), and osteoclast-stimulatory transmembrane protein (OC-STAMP). These effects were achieved by inhibiting the RANKL-mediated activation of MAPK signaling pathway proteins, including p38, ERK, and JNK. In vivo, ES attenuated OVX-induced decrease in bone volume to tissue volume ratio (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), and bone mineral density, but increased trabecular separation (Tb.Sp) in the femur. Collectively, our findings showed that ES inhibited RANKL-activated osteoclast differentiation in bone marrow macrophages and prevented OVX-mediated bone loss in rats. These findings suggest that ES has the potential to be used as a therapeutic agent for bone-related diseases, such as osteoporosis.     

Rapid Clearance of IR783 and Methyl-β-cyclodextrin Complex for Improved Tumor Imaging

Near-infrared (NIR) fluorescence cancer imaging with targeted NIR fluorophores holds considerable promise for accurate detection and cancer diagnosis. Among the various NIR heptamethine cyanine dyes reported previously, IR783 as a single small molecule has been widely used for tumor-targeted imaging without the additional conjugation of targeting moieties. Despite the potential advantages of IR783, the major problems, such as its non-specific uptake in normal tissues/organs and slow clearance, remain to be solved. A key determinant of sensitivity and detectability in tumor imaging is the improvement of the tumor-to-background ratio (TBR). Herein, a simple and effective supramolecular complex self-assembled from IR783 and methyl-β-cyclodextrin is developed to improve tumor imaging accompanied by rapid clearance from the body. The IR783-cyclodextrin complex allowed for rapid whole body biodistribution, which remarkably reduced non-specific background uptake, and thus increased the TBR value within 24 h post-injection. Therefore, this strategy is applicable in combination with many different types of carbocyanine dyes for improved tumor imaging.