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We reported a one-pot enantioselective three-component vinylogous Michael/aldol tandem reaction of prochiral 3-alkylidene oxindoles with methyleneindolinones and aldehydes using bifunctional organocatalysts. A variety of enantioenriched 3,3-disubstituted oxindoles

A dimeric dithiolate-bridged species, [Fe(NO)(PS2)]

Carbon monoxide (CO) plays an important role in signaling in cells, making its use as a therapeutic tool highly intriguing. Reduced burst emissions are important to avoid the cytotoxicity and tissue damage caused by CO. Here, we developed a stable diiron carbonyl [FeFe] hydrogenase agent that enables prolonged CO release activity (half-life of over 9 h) in cells. The integrated analysis allowed the identification of the key intermediate sites and CO accumulations with subcellular resolution. We observed that the [FeFe]

We here described a direct catalytic asymmetric functionalization of 2-methylindoles using organocatalysis. An efficient asymmetric allylic alkylation reaction with respect to 2-methyl-3-nitroindoles and racemic Morita–Baylis–Hillman carbonate has been achieved by using a chiral biscinchona alkaloid catalyst, which provided the functionalized indole derivatives in good yields and enantioselectivities.

Light triggers the formation of HNO from a metal-nitrosyl species, facilitated by an intramolecular pendant thiol proton. Two {FeNO}6 complexes (the Enemark-Felthan notation), [Fe(NO)(TMSPS2)(TMSPS2H)] (1, TMSPS2H2 = 2,2'-dimercapto-3,3'-bis(trimethylsilyl)diphenyl)phenylphosphine; H is a dissociable proton) with a pendant thiol and [Fe(NO)(TMSPS2)(TMSPS2CH3)] (2) bearing a pendant thioether, are spectroscopically and structurally characterized. Both complexes are highly sensitive to visible light. Upon photolysis, complex 2 undergoes NO dissociation to yield a mononuclear Fe(III) complex, [Fe(TMSPS2)(TMSPS2CH3)] (3). In contrast, the pendant SH of 1 can act as a trap for the departing NO radical upon irradiation, resulting in the formation of an intermediate A with an intramolecular [SH···ON-Fe] interaction. As suggested by computational results (density functional theory), the NO stretching frequency (νNO) is sensitive to the intramolecular interaction between the pendant ligand and the iron-bound NO, and a shift of νNO from 1833 (1) to 1823 cm-1 (A) is observed experimentally. Subsequent photolysis of the intermediate A results in HNO production and a thiyl group that then coordinates to the Fe center for the formation of [Fe(TMSPS2)2] (4). In contrast with the common acid-base coupling pathway, the HNO is not voluntarily yielded from 1 but rather is generated by the photopromoted pathway. The photogenerated HNO can further react with [MnIII(TMSPS3)(DABCO)] (TMSPS3H3 = (2,2'2''-trimercapto-3,3',3''-tris(trimethylsilyl)triphenylphosphine; DABCO = 1,4-diazabicyclo[2.2.2]octane) in organic media to yield anionic [Mn(NO)(TMSPS3)]- (5-) with a {MnNO}6 electronic configuration, whereas [MnIII(TMSPS3)(DABCO)] reacts with NO gas for the formation of a {MnNO}5 species, [Mn(NO)(TMSPS3)] (6). Effective differentiation of the formation of HNO from complex 1 with the pendant SH versus NO from 2 with the pendant SMe is achieved by the employment of [MnIII(TMSPS3)(DABCO)].

Hexa-peri-hexabenzocoronene (HBC) derivatives tend to form discotic columnar liquid crystalline (DCLC) phases capable of charge transport and anisotropic photoresponses. However, their noncovalentl...

We here described a direct catalytic asymmetric functionalization of 2-methylindoles using organocatalysis. An efficient asymmetric allylic alkylation reaction with respect to 2-methyl-3-nitroindoles and racemic Morita-Baylis-Hillman carbonate has been achieved by using a chiral biscinchona alkaloid catalyst, which provided the functionalized indole derivatives in good yields and enantioselectivities.

Light triggers the formation of HNO from a metal-nitrosyl species, facilitated by an intramolecular pendant thiol proton. Two {FeNO}

In recent years, with the gradual completion of different GNSS constellations, the available L-band navigation signals have become more abundant. Not only can they be used for PNT (Positioning, Navigation, and Timing), but the reflected signals can also be used for retrieving a variety of geophysical parameters such as sea surface height. Coastal GNSS-R (Global Navigation Satellite System Reflectometry) code delay altimetry obtains the path delay measurements between reflected signal and corresponding direct signal based on ranging code. And the height from sea surface to antenna can be calculated according to the geometric relationship of sea surface altimetry. In order to achieve path delay with higher accuracy, we performed coastal GNSS-R altimetry experiment on a trestle using GPS L5 signals with high ranging code rate. The digital IF (intermediate frequency) data at 25 MHz sample rate were collected during the experiment. Then, self-developed software-defined receiver was used to process the IF data. As the code modulation methods of in-phase (I component) and quadrature-phase (Q component) on GPS L5 carrier are different, we tested the accuracy of I and Q component for sea surface altimetry, separately. In addition, considering different coherent integration time have a certain impact on the accuracy, 1 ms and 10 ms coherent integration time are adopted to compute the path delay based on I and Q component. The results show: for 1 ms coherent integration, the RMSE of I and Q component are 0.70 m and 0.61 m, respectively; while the coherent integration time is 10 ms, the RMSE of I and Q component are 0.54 m and 0.43 m, respectively. To sum up, increasing coherent integration time can improve the accuracy; the altimetry accuracy of the Q component signal is better than that of I component signal.

An efficient asymmetric Michael reaction of 1,3-dicarbonyl compounds with α-Substituted-β-Nitroacrylates has been developed by using a cinchona-thiourea bifunctional organocatalyst in high yields and enantioselectivies. One of adducts could be transformed into a chiral β-nitroester bearing an isoxazole skeleton and an all-carbon quaternary chiral center.

We use an econometrically distinct method to test whether the value relevance of financial statements, especially during convergence with International Financial Reporting Standards (IFRS), has improved in Taiwanese firms in 1990–2011. In contrast to a prior study, our results show that given transformation between two high-quality accounting standards, convergence with IFRS will not lead to further increases in value relevance of financial statements. Our findings may provide implications for international standard-setters and regulators, especially countries undecided about adopting or converging with IFRS.

Both the reduced and the protonated states of diiron dithiolate complexes, which are key intermediate species for the electrocatalytic production of hydrogen, have been spectroscopically and theoretically investigated in this study. Five important states in the process of H2 evolution have been characterized. In the presence of a superacid, protonation occurs onto the Fe–Fe vector of [(μ-xdt)Fe2(CO)6] (xdt: pdt, 1,3-propanedithiolate; edt, 1,2-ethanedithiolate; bdt, 1,2-benzenedithiolate) to yield the cationic μ-H species (the C state). A single reduction at 193 K leads to the neutral species (the CE state), with similar structures for the pdt and edt bridgeheads. The CE species of the bdt analogue is unstable under the same conditions. An open structure resulting from the rupture of one Fe–S bond is suggested by DFT calculations. Subsequently, a second reduction induces a dramatic structural rearrangement in which the CEE state possesses an open structure exhibiting a μ-H and a μ-CO group. Protonation on...

Biomimetic diiron complexes bearing redox non-innocent ligands are discussed in this review. The complexes are synthesized to model the active site of [FeFe] hydrogenase in order to elucidate the catalytic mechanism of H2 evolution and design superior artificial catalysts. Employment of the redox active ligands serves an important factor to modulate electronic structure of the Fe2 core as the similar functionality exerted by the [4Fe4S] cofactor within the H-cluster. Different types of redox active ligands are summarized. The influence of their ligation is observable in spectroscopy as well as cyclic voltammetry, and studied by theoretical calculation.

The intrinsic catalytic property of a Fe–S complex toward H2 evolution was investigated in a wide range of acids. The title complex exhibited catalytic events at −1.16 and −1.57 V (vs Fc+/Fc) in the presence of trifluoromethanesulfonic acid (HOTf) and trifluoroacetic acid (TFA), respectively. The processes corresponded to the single reduction of the Fe-hydride-S-proton and Fe-hydride species, respectively. When anilinium acid was used, the catalysis occurred at −1.16 V, identical with the working potential of the HOTf catalysis, although the employment of anilinium acid was only capable of achieving the Fe-hydride state on the basis of the spectral and calculated results. The thermodynamics and kinetics of individual steps of the catalysis were analyzed by density functional theory (DFT) calculations and electroanalytical simulations. The stepwise CCE or CE (C, chemical; E, electrochemical) mechanism was operative from the HOTf or TFA source, respectively. In contrast, the involvement of anilinium acid mo...

A reversible and temperature-dependent proton-relay process is demonstrated for a Fe2 complex possessing a terminal thiolate in the presence of nitrogen-based acids. The terminal sulfur site (S(t) ) of the complex forms a hydrogen-bond interaction with N,N-dimethylanilinium acid at 183 K. The Fe2 core, instead, is protonated to generate a bridging hydride at 298 K. Reversibility is observed for the tautomerization between the hydrogen-bonded pair and the Fe-hydride species. X-ray structural analysis of the hydrogen-bonded species at 193 K reveals a short N(H)⋅⋅⋅S(t) contact. Employment of pyridinium acid also results in similar behavior, with reversible proton-hydride interconversion. DFT investigation of the proton-transfer pathways indicates that the pKa value of the hydrogen-bonded species is enhanced by 3.2 pKa units when the temperature is decreased from 298 K to 183 K.

Eight new diiron carbonyl dithiolate complexes, [(μ-xdt)Fe2(CO)5(L)]; xdt = bdt, L = dppmBH3 (2), dppeBH3 (2a), dppm (2b), xdt = edt, L = dppmBH3 (4), dppeBH3 (4a), xdt = Bn-adt, L = dppmBH3 (5), dppeBH3 (5a), and [(μ-bdt)Fe2(CO)4(μ-dppm)], (3), have been prepared and characterized by FTIR, NMR spectroscopy and X-ray single crystallography. Molecular structures of complexes 2–5 reveal that the Fe2 core exhibits a butterfly conformation and each Fe center is of the pseudo-square-pyramidal coordination geometry. For the mono-substituted species, the phosphine ligand is located in the axial position. For the di-substituted species, the phosphine ligand is spanned between two Fe sites, occupying the basal position. The attached borane unit exerts electronic withdrawing influence on the electron richness about the Fe center. When the phosphine pendant is not protected by borane, coordination to the adjacent Fe site occurs under the reducing condition. It allows synthesis of 3 from chemical or electrochemical reduction of 2b. Electrocatalysis of acetic acid by complexes 2–5 is studied. The bdt derivatives are reduced at a potential 300 mV more positive than the edt and adt analogs. For the latter species, electrocatalytic events occur near the first reduction. In contrast, no catalysis is observed for 2 in the available electrochemical windows. The rate constant of the catalytic reaction by the species is measured. The adt derivative reveals the highest efficiency toward hydrogen production from acetic acid.

Divided wall columns (DWCs) can save energy and capital costs compared with traditional distillation columns; however, the design of DWCs is more difficult because there are more degrees of freedom...

The one-electron oxidations of a Fe2 complex lead to the formation of a persistent metal-stabilized thiyl radical Fe2 species, mixed-valent Fe4, and Fe8 complexes. The unpaired spin in the Fe2 radical species delocalizes over the Fe2 and the aromatic dithiolate, mostly on the terminal sulfur. The subsequent dimerization of the singly oxidized Fe2 to the Fe4 retains the partial thiyl radical character. For an analogue with less steric hindrance, the π-π stacking interaction between the dithiolato aromatic rings induces generation of the Fe8, in which process electronic structures of the species are modulated through reducing the thiyl radical to the thiolate. Electronic reorganization repeats when the Fe8 is converted to Fe4. Electronic interplay in the complexes decreases the energy gap of frontier MOs and buffers electronic impacts upon redox events. Easier accessible redox potentials and increased stability of the species are facilitated. The results demonstrate that electronic versatility of the benzenedithiolate exerts pronounced influences on electronic and coordination structure of the metal complexes.

This study examines the effects of chloride on the partitioning and speciation of heavy metal during waste combustion by using simulated municipal solid wastes (MSW). The results indicate that increasing the chloride content of the waste and the combustion temperature may cause the formation of volatile heavy metal compounds, thus increasing metal partitioned to the fly ash and the flue gases. As identified by X-ray diffraction (XRD), speciation is found to be primarily influenced by the reactive affinity of the heavy metals, the types of chlorides, and the metal concentrations in the waste.

The effect of organic chloride derived from PVC and other possible sources in wastes, on the partitioning and speciation of heavy metals and their compounds, during Municipal Solid Wastes (MSW) incineration was studied using a laboratory tube furnace and simulated waste spiked with organic chloride. The results indicated that an increase in the organic chloride content and combustion temperature might increase the volatility of heavy metals and/or their compounds in the wastes, thus, increasing metal partitioning in the fly ash or the flue gases. Metal oxides were the major metal species found in the bottom ash, as identified by X‐ray diffraction (XRD) analysis, regardless of the addition of organic chlorides, while several other metal chlorides were also found when spiked at higher concentrations.

The flow behavior of polycarbonate (PC) blended with three kinds of polyolefins (LDPE, HDPE, PP) was studied at 260°C using an Instron Capillary Rheometer. Flow behavior of the blends was found to be very different from that of the individual components, and significant viscosity reductions were observed for blends consisting of 5% and 15% polyolefins. In particular, the viscosity of PC/HDPE was found to be much lower than that of the parent viscosity at a shear rate below 100 1/s. For pure components, a crossover of PC viscosity was observed at high shear rate for HDPE and PP. Interfacial slippage in the blends has been suggested as the flow mechanism by which a substantial reduction in the melt viscosities of either component takes place upon the addition of a small amount of the other. A new method was proposed to evaluate the relationship between the characteristic slip factor of the blend and the viscosity of the mixture. A single master curve was obtained, i.e., σm/αAB = a · p±b, where σm is the shear stress at the matrix, αAB the slip factor, p the viscosity ratio, and a, b the constants. © 1994 John Wiley & Sons, Inc.

The first di-protonated [FeFe] hydrogenase model relevant to key intermediates in catalytic hydrogen production is reported. The complex bearing the S-proton and Fe-hydride is structurally and spectroscopically characterized as well as studied by DFT calculations. The results show that the thiolate sulfur can accept protons during the catalytic routes.