Photoinduced Copper-Catalyzed 1,2-Difunctionalization of 1,3-Dienes with Aryl Diselenides.

Described herein is a photoinduced copper-catalyzed 1,2-difunctionalization of 1,3-dienes. The selenium atom radical was generated by the visible light irradiation of diselenides, triggering radical addition with 1,3-dienes to form allyl radical intermediate. Subsequent rapid Z/E isomerization allowed for thermodynamically favorable intermediate formation and enabled copper catalyzed stereoselective functionalization with various nucleophiles.

Visible-Light-Mediated Radical Hydroalkylative Cyclization of 1,6-Enynes.

A radical hydroalkylative cyclization approach accessing various alkenyl heterocyclic compounds was developed using dimethyl malonate and 1,6-enynes in the presence of visible-light photoredox catalysis. The use of Ir(dtbbpy)(ppy)2PF6 as a photosensitizer enables carbon atom radical formation and initiates the cascade cyclization reaction under mild conditions.

Visible-Light Mediated Diarylselenylative Cyclization of 1,6-Enynes.

We herein described a selenylative cyclization reaction of enynes by the utilization of diselenides as radical sources. The visible-light irradiation of the reaction mixture enables the generation of the selenium atom radical to trigger the radical addition/cyclization/selenation sequences. Both terminal alkyne and internal alkyne derived 1,6-enynes were tested and suitable for the current synthetic protocol, delivering various kinds of selenium-containing cycles in good yields.

Solid-State (63)Cu, (65)Cu, and (31)P NMR Spectroscopy of Photoluminescent Copper(I) Triazole Phosphine Complexes.

The results of a solid-state (63/65)Cu and (31)P NMR investigation of several copper(I) complexes with functionalized 3-(2'-pyridyl)-1,2,4-triazole and phosphine ligands that have shown potential in the preparation of photoluminescent devices are reported. For each complex studied, distinct NMR parameters, with moderate (63)Cu nuclear quadrupolar coupling constant (CQ) values ranging from -17.2 to -23.7 MHz, are attributed to subtle variations in the distorted four-coordinate environments about the copper nuclei. The spans of the copper chemical shift (CS) tensors, δ11-δ33, for the mono- and bisphosphine complexes are also similar, ranging from 1000 to 1150 ppm, but that for a complex with a strained bidentate phosphine ligand is only 650 ppm. The effects of residual dipolar and indirect spin-spin coupling arising from the (63/65)Cu- (31)P spin pairs, observed in the solid-state (31)P NMR spectra of these complexes, yield information about the orientations of the copper electric field gradient (EFG) tensors relative to the Cu-P bond. Variable-temperature (31)P NMR measurements for [Cu(bptzH)(dppe)]ClO4 (bptzH = 5-tert-butyl-3-(2'-pyridyl)-1,2,4-triazole; dppe = 1,2-bis(diphenylphosphino)ethane), undertaken to investigate the cause of the broad unresolved spectra observed at room temperature, demonstrate that the broadening arises from partial self-decoupling of the (63/65)Cu nuclei, a consequence of rapid quadrupolar relaxation. Ab initio calculations of copper EFG and CS tensors were performed to probe relationships between NMR parameters and molecular structure. The analysis demonstrated that CQ((63/65)Cu) is negative for all complexes studied here and that the largest components of the EFG tensors are generally coincident with δ11.

Visible-Light-Induced Stereoselective Radical trans-Iodoalkylation of Terminal Alkyne with Iodoform.

We describe herein a novel stereoselective trans-iodoalkylation protocol by using three components of nucleophilic dicarbonyl compounds, iodoform and terminal alkynes. The generation of tertiary carbon radical species under mild reaction conditions allows this radical addition and stereoselective iodine atom transfer sequence with terminal alkyne to access highly synthetic applicable disubstituted vinyl iodide. The synthetic application of the present three-component photochemical protocol was demonstrated by the gram-scale reaction and product derivatization.

Dispersion-induced cooperative hydrogen atom transfer for radical iodoalkylation.

Described herein is a novel visible-light-promoted three-component radical iodo-alkylative cyclization of alkynes using iodoform as a bifunctional iodine atom source. Visible-light irradiation of a polar-polar interaction complex of iodoform with malonate enables the cooperative hydrogen atom transfer process to generate alkyl radical and trigger a cascade reaction sequence.

Site-Specific Radical Alkylation of Aryl Cyanide: Visible-Light, Photoredox-Catalyzed, Three-Component Arylalkylation of [1.1.1]Propellane.

We report herein a three-component radical arylalkylation of [1.1.1]propellane toward the synthesis of aryl-substituted bicyclo[1.1.1]pentane derivatives. The use of electron-deficient aryl cyanide as an aryl group source not only reduces the energy barrier of the arylation of the nucleophilic alkyl radical species, but also suppresses the electrophilic Friedel-Crafts alkylation process, enabling the present site-selective arylalkylation.

Visible-light-induced ligand to metal charge transfer excitation enabled phosphorylation of aryl halides.

We herein described a visible light induced nickel(II)-catalyzed cross-coupling of secondary phosphine oxides with aryl halides. The Ni(I) species and chlorine atom radical Cl˙ were generated via the ligand to metal charge transfer (LMCT) process of the NiCl2(PPh3)2, which allows nickel(IV)-phosphorus species in situ formation, giving various tertiary phosphine oxides under photocatalyst-free conditions.

FeO-Based Hierarchical Structures on FTO Substrates and Their Photocurrent.

As one of the most promising photoanode materials for photoelectrochemical (PEC) water oxidation, earth-abundant hematite has been severely restricted by its poor electrical conductivity, poor charge separation, and sluggish oxygen evolution reaction kinetics. FeO has an ability to produce hydrogen, while its preparation needs high temperature to reduce Fe3+ to Fe2+ by using H2 or CO gases. Here, Fe2O3- and FeO-based nanorods (NRs) on fluorine-doped tin oxide (FTO) substrate have been prepared, where the latter was obtained by doping Sn4+ ions in FeOOH to reduce Fe3+ ions to Fe2+. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements indicate that the dominant content of Fe element on the surface of Sn-doped Fe2O3 and Sn-FeOOH samples is Fe2+. FeO-based NRs have a Fe3O2/FeO heterostructure with some SnO2 nanoparticles distributed on their surface. These prepared samples were used as PEC photoanodes under a visible-light irradiation. The results showed that the modified FeO-based NRs have a photocurrent density of 0.2 mA cm-2 at 1.23 V vs reference hydrogen electrode (RHE) using Hg/HgO electrode as the reference electrode. Furthermore, they also have a better photocatalytic hydrogen evolution activity with a rate of 2.3 µmol h-1 cm-1. The improved photocurrent and photocatalytic activity can be ascribed to the Sn-dopant, as the introduction of Sn4+ not only leads to the formation of the Fe3O2/FeO heterostructure but also increases the carrier concentration. Fe3O2/FeO heterostructure with SnO2 nanoparticles on its surface has a good band energy alignment, which is beneficial to the PEC water oxidation and reduction.

Nanostructured FeNi3 Incorporated with Carbon Doped with Multiple Nonmetal Elements for the Oxygen Evolution Reaction.

The sluggish oxygen evolution reaction (OER) through water electrolysis is still challenging. Herein, a facile approach to fabricate highly efficient nanostructured FeNi3 incorporated on carbon doped with multiple nonmetal elements (FeNi3 /M-C) was prepared by annealing an in situ polymerized metal complex from economical precursors. The temperature dependence of the structure and the catalytic performance for the OER was probed. The best pyrolysis temperature was 800 °C, at which the fabricated material exhibited the highest catalytic performance for the OER. Specifically, an overpotential as low as 246 mV (no IR correction) afforded 10 mA cm-2 with a low Tafel slope of 40 mV dec-1 , exceeding that of the best noble-metal catalyst IrO2 and other similar Fe-Ni alloys. High catalytic efficiency and anticorrosion ability towards the OER were displayed in terms of high specific surface area, rapid kinetics, high stability, and specific activity. The excellent performance was correlated to the structure and the modest graphitization degree of carbon and an appropriate ratio between graphitic and pyridinic N atoms and the synergistic effect between the Fe-Ni alloy active sites and the conducting carbon doped with multiple nonmetal elements. Moreover, as a powder catalyst, it could be applied in a real polymer electrolyte membrane electrolyzer. These results are helpful for understanding the improved catalytic activity and the promotion of the catalytic efficiency of the Fe-Ni alloy materials for the OER.

Electrochemical oxygen evolution reaction efficiently boosted by thermal-driving core-shell structure formation in nanostructured FeNi/S, N-doped carbon hybrid catalyst.

Water electrolysis has not yet been implemented on a large scale due to the sluggish oxygen evolution reaction (OER). Herein, we for the first time discover an interesting core-shell structure formation driven by the Kirkendall effect in a nanostructured FeNi alloy incorporating S, N-doped carbon (FeNi/SN-C) and this structural transformation can greatly boost the alloy's catalytic ability for OER. Thermal annealing of FeNi/SN-C in air induces the formation of an Fe-rich Fe-Ni oxide shell over the Fe-Ni alloy core due to the different metal diffusion rates and oxygen coupling abilities. As a powder catalyst, an overpotential as low as 230 mV can drive 10 mA cm-2, about 30 mV less than the original catalyst; it outperforms most nonprecious metal catalysts and noble commercial IrO2 catalysts. The catalytic performances are probably derived from the oxidized Fe-rich oxidation shell in contact with the conductive FeNi/SN-C host, which chemically stabilizes and further activates the active sites formed during the reaction. It is also concluded that exposure of the metal oxide shell contributes more to the activity than the large surface area contributed by the porous carbon matrix. This work puts forward a novel and efficient strategy to optimize Fe-Ni-based catalysts for OER by in situ structure and morphology tuning.

Periosteum Extracellular-Matrix-Mediated Acellular Mineralization during Bone Formation.

Cell-mediated mineralization is essential for bone formation and regeneration. In this study, it is proven that extracellular matrix (ECM) of decellularized periosteum can play an initiative and independent role in bone-like apatite formation. Using decellularized periosteum scaffold, it is revealed that ECM scaffold itself can promote critical bone defect regeneration and nude mouse ectopic ossification. The natural collagen matrix of decellularized periosteum can serve as a 3D structural template for Ca-P nuclei initiation, controlling the size and orientation of bone-like mineral crystals. The naturally cross-linked and highly ordered 3D fibrillar network of decellularized periosteum not only provides a model for mimicking mineralization in vitro and in vivo to elucidate the important functions of ECM in bone formation and regeneration, but also can be a promising biomaterial for bone tissue engineering and clinical application.

Spectroscopic studies on the interaction between 3,4,5-trimethoxybenzoic acid and bovine serum albumin.

The interaction between 3,4,5-trimethoxybenzoic acid (TMBA) and bovine serum albumin (BSA) was studied by fluorescence and UV-vis absorption spectroscopy. In the mechanism discussion, it was proved that the fluorescence quenching of BSA by TMBA is a result of the formation of TMBA-BSA complex. Quenching constants were determined using the Stern-Volmer equation to provide a measure of the binding affinity between TMBA and BSA. The thermodynamic parameters DeltaH, DeltaG, DeltaS at different temperatures were calculated, and electrostatic interactions play an important role to stabilize the complex. The distance r between donor (BSA) and acceptor (TMBA) was obtained according to fluorescence resonance energy transfer (FRET).

Luminescent dinuclear copper(I) complexes bearing 1,4-bis(diphenylphosphino)butane and functionalized 3-(2'-pyridyl)pyrazole mixed ligands.

A family of new dinuclear Cu(i) complexes with 1,4-bis(diphenylphosphino)butane (dppb) and functionalized 3-(2'-pyridyl)pyrazole mixed ligands has been synthesized and characterized. It is revealed that all these Cu(i) complexes include a [Cu2(dppb)2](2+) framework with the two Cu(i) atoms doubly bridged by a pair of dppb to generate a fourteen-membered Cu2P4C8 ring, and functionalized 3-(2'-pyridyl)pyrazole adopts a neutral chelating coordination mode without the N-H bond cleavage of the pyrazolyl ring. All these dinuclear Cu(i) complexes display a relatively weak low-energy absorption in CH2Cl2 solution, which is closely related to the variation of the Cu-N and Cu-P bonds caused by the substituent on the pyrazolyl ring. These dinuclear Cu(i) complexes are all emissive in solution and solid states at ambient temperature, which can be well modulated through structural modification of 3-(2'-pyridyl)pyrazole. It is shown that introduction of the trifluoromethyl group into the pyrazolyl ring is helpful for enhancing the luminescence properties of Cu(i) pyrazole phosphine complexes.

Microcalorimetric studies of the action of Na2SeO3 on the growth of Halobacterium halobium R1.

The effect of Na2SeO3 on the growth of Halobacterium halobium R1 was investigated by means of microcalorimetry at 37 degrees C. The biological response to toxicants is observed as the inhibition of the rate constant of growth of living cells. A low concentration of Na2SeO3 stimulated the growth of H. halobium R1, and a high concentration of Na2SeO3 inhibited the growth of H. halobium R1. Toxicity may be expressed as the half-inhibition concentration (IC50). The rate constants of growth (k) and the concentrations of Na2SeO3 (c) shows a linear relationship: k = 1.790 x 10(-6) -- 2.27 x 10(-3) c. The value of IC50 obtained from the accompanying figure of I-c is 679 microg/mL.

Structure and physicochemical properties of starches in lotus (Nelumbo nucifera Gaertn.) rhizome.

The type and content of starch are believed to be the most critical factors in determining the storage and processing quality of lotus rhizome species, and the intention of this study is to survey the structure and properties of starches isolated from rhizomes of two lotus cultivars using X-ray powder diffraction, solid-state nuclear magnetic resonance spectroscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, scanning electron microscope, differential scanning calorimetry, and rapid viscosity analyzer (RVA). Starch in rhizome of cultivar Meirenhong exhibited C-type X-ray diffraction pattern, while starch in rhizome of cultivar Wawalian showed A-type pattern. (13)C cross-polarization magic-angle spinning nuclear magnetic resonance ((13)C CP-MAS NMR) also confirmed the polymorphs. The relative crystallinity of two starches was quantitatively estimated from two methods and compared. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) results indicated that the external regions of the starch granules had a great level of ordered structure. Starch granules in Meirenhong showed oval-shaped granules, while starch granules in Wawalian were elongated and oval in shape with relatively large size. Gelatinization temperatures of starch in Meirenhong and Wawalian were 330.5 and 342.4 K, respectively, and the gelatinization temperature range of Meirenhong was significantly wider than that of Wawalian. Starch in rhizome of cultivar Meirenhong showed lower pasting temperature, lower hot and cool viscosities, lower setback, and higher peak viscosity and breakdown than those of Wawalian in RVA pasting profiles at 6% starch concentration.

Characterization and antioxidant activity of the complex of tea polyphenols and oat ß-glucan.

Few data are available about the effects of complexation of polyphenols with polysaccharide on their bioavailability. The complex of tea polyphenols (TP) with oat ß-glucan was characterized by ultraviolet-visible spectrometry, Fourier transform infrared spectrometry, differential scanning calorimetry, atomic force microscopy, and solid-state (13)C NMR spectroscopy. The results indicated that the bonds which governed the interaction between TP and oat ß-glucan were strong hydrogen bonds. The in vitro antioxidant activity of TP, ß-glucan, their complex, and physical mixture was assessed using four systems, namely, DPPH(•), OH(•), and O(2)(•-) scavenging activities and reducing power. The complexation and blending of TP and ß-glucan exhibited different impacts on the index of in vitro and in vivo antioxidant capacities. In the concentration range of 0.5-2.5 mg mL(-1), the complex had highest O(2)(•-) scavenging activity, whereas the highest OH(•) scavenging activity was found with the physical mixture. For antioxidant testing in vivo, there was no significant difference between the complex and the physical mixture in terms of glutathione peroxidase activity and levels of malondialdehyde and total antioxidant capacity in serums. However, the complex exhibited much higher activities of superoxide dismutase and glutathione peroxidase in livers than the physical mixture. The present study provided a deeper understanding of the influence of molecular interaction between TP and oat ß-glucan on their antioxidant activities.

Anatomical and chemical characteristics of culm of rice brittle mutant bc7(t).

Brittleness culm is an important agronomic trait that has a potential usefulness in agricultural activity as animal forage. In the present study, the anatomy of culm of rice (Oryza sativa L.) brittle mutant bc7(t) was investigated with light microscopy and electron microscopy. Findings showed bc7(t) exhibited higher area percentages of mechanical and conducting tissues, and lower cell wall thickness of sclerenchyma cells. Chemical analyses and 13C CP/MAS NMR spectra of cell walls indicated that the content of cellulose decreased, and the contents of hemicellulose, lignin and silicon was increased in bc7(t). Lignin histochemical staining and cytochemical localisation revealed that the higher lignin was localised in epidermal, sclerenchyma and vascular bundle cells in bc7(t). The energy dispersive X-ray microanalysis showed that the contents of silicon were higher in bc7(t) than in the wild type. These results indicate that cellulose, hemicellulose, lignin, silicon and the area percentages of mechanical and conducting tissues could be regulated in a compensatory fashion, possibly contributing to metabolic flexibility and a growth advantage to sustain the bc7(t) normal growth habit like the wild-type plant.

Granule structure and distribution of allomorphs in C-type high-amylose rice starch granule modified by antisense RNA inhibition of starch branching enzyme.

C-type starch, which is a combination of both A-type and B-type crystal starch, is usually found in legumes and rhizomes. We have developed a high-amylose transgenic line of rice (TRS) by antisense RNA inhibition of starch branching enzymes. The starch in the endosperm of this TRS was identified as typical C-type crystalline starch, but its fine granular structure and allomorph distribution remained unclear. In this study, we conducted morphological and spectroscopic studies on this TRS starch during acid hydrolysis to determine the distribution of A- and B-type allomorphs. The morphology of starch granules after various durations of acid hydrolysis was compared by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The results showed that amorphous regions were located at the center part of TRS starch subgranules. During acid hydrolysis, starch was degraded from the interior of the subgranule to the outer surface, while the peripheral part of the subgranules and the surrounding band of the starch granule were highly resistant to acid hydrolysis. The spectroscopic changes detected by X-ray powder diffraction, 13C cross-polarization magic-angle spinning NMR, and attenuated total reflectance Fourier transform infrared showed that the A-type allomorph was hydrolyzed more rapidly than the B-type, and that the X-ray diffraction profile gradually changed from a native C-type to a CB-type with increasing hydrolysis time. Our results showed that, in TRS starch, the A-type allomorph was located around the amorphous region, and was surrounded by the B-type allomorph located in the peripheral region of the subgranules and the surrounding band of the starch granule. Thus, the positions of A- and B-type allomorphs in the TRS C-type starch granule differ markedly from those in C-type legume and rhizome starch.

C-type starch from high-amylose rice resistant starch granules modified by antisense RNA inhibition of starch branching enzyme.

High-amylose starch is a source of resistant starch (RS) which has a great benefit on human health. A transgenic rice line (TRS) enriched amylose and RS had been developed by antisense RNA inhibition of starch branching enzymes. In this study, the native starch granules were isolated from TRS grains as well as the wild type, and their crystalline type was carefully investigated before and after acid hydrolysis. In high-amylose TRS rice, the C-type starch, which might result from the combination of both A-type and B-type starch, was observed and subsequently confirmed by multiple physical techniques, including X-ray powder diffraction, solid-state nuclear magnetic resonance, and Fourier transform infrared. Moreover, the change of starch crystalline structure from C- to B-type during acid hydrolysis was also observed in this RS-rich rice. These data could add to our understanding of not only the polymorph structure of cereal starch but also why high-amylose starch is more resistant to digestion.