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Herein, a practical and robust methodology for photoinduced decarboxylative and dehydrogenative cross-coupling is reported.

Metal-metal cooperativity is emerging as an important strategy in catalysis. This requires appropriate ligand scaffolds that can support two metals in close proximity. Here we report nickel-promoted formation of a dinucleating planar macrocyclic ligand that can support bimetallic dinickel(II) and dinickel(I) complexes. Reaction outcomes can be tuned by variation of the substituents and reaction conditions to favour dinucleating macrocyclic, mononucleating macrocyclic or conventional pincer architectures.

Computational studies show that the activity of ATRP catalysts can be dramatically improved using quinuclidine bridgehead ligands.

As the desired sulfur host of lithium-sulfur battery, the strong polarity and fast electron migration capability are indispensable for achieving effective adsorption and conversion of lithium polysulfides (LiPSs), that is, restricting the shuttle effect. Herein a porous microdisk Ti4O7/TiN/C heterojunction with strong polar N-Ti-O covalent bonds is precisely constructed. Compared with O-Ti-O or N-Ti-N bond in single Ti4O7 or TiN, the N-Ti-O bond with stronger polarity could adsorb and bond with S and Li atoms in LiPSs, which is beneficial for LiPSs adsorption. Beside, the Ti4O7/TiN heterostructure favors the electron transfer, which could promote the conversion of LiPSs. The design strategy is to construct abundant polar N-Ti-O bonds at Ti4O7/TiN heterogeneous interface that would realize the associative process of LiPSs adsorption, trapping, and conversion, thereby restraining the shuttle effect efficiently. In the current study, as the host of the sulfur cathode, the porous microdisk TiN/Ti4O7/C heterojunction exhibits a high specific capacity of 1204.5 mAh g−1 at 0.2 C, and a high specific capacity of 616.5 mAh g−1 at an ultrahigh current density of 4 C. In addition, 86.4% and 116.9% capacity are retained over 1000 cycles at 1 C and 2 C, respectively. This strategy provides an insight into developing lithium-sulfur battery with extraordinary performance, and opens promising routes to design the next-generation electrochemical energy storage devices.

Herein, a protocol for the copper-catalyzed direct monofluoroalkenylation of C(sp3)–H bonds is reported.

Luciferin is one of Nature's most widespread luminophores, and enzymes that catalyze luciferin luminescence are the basis of successful commercial "glow" assays for gene expression and metabolic ATP formation. Herein we report an electrochemical method to promote firefly's luciferin luminescence in the absence of its natural biocatalyst-luciferase. We have gained experimental and computational insights on the mechanism of the enzyme-free luciferin electrochemiluminescence, demonstrated its spectral tuning from green to red by means of electrolyte engineering, proven that the colour change does not require, as still debated, a keto/enol isomerization of the light emitter, and gained evidence of the electrostatic-assisted stabilization of the charge-transfer excited state by double layer electric fields. Luciferin's electrochemiluminescence, as well as the in situ generation of fluorescent oxyluciferin, are applied towards an optical measurement of diffusion coefficients.

Benzamidinium compounds have found widespread use in both medicinal and supramolecular chemistry. In this work, we show that benzamidiniums hydrolyse at room temperature in aqueous base to give the corresponding primary amide. This reaction has a half-life of 300 days for unsubstituted benzamidinium at pH 9, but is relatively rapid at higher pHs (e.g. t1/2 = 6 days at pH 11 and 15 hours at pH 13). Quantum chemistry combined with first principles kinetic modelling can reproduce these trends and explain them in terms of the dominant pathway being initiated by attack of HO– on benzamidine. Incorporation of the amidinium motif into a hydrogen bonded framework offers a substantial protective effect against hydrolysis.

The full catalytic cycle of the proline-catalyzed intermolecular aldol reaction of acetone and p-nitrobenzaldehyde in acetone solvent has been investigated by quantum chemistry at the G3(MP2,CC)//M062X/6–31+G(d)/SMD level of theory, and the results used to develop an ab initio kinetic model. Proline catalyzes the aldol reaction according to the enamine mechanism. The initial reaction between proline and acetone was reinvestigated, and a revised mechanism for enamine formation is proposed in which a second proline assists the process contributing to the enamine formation. Using various initial concentrations of proline while keeping the experimental ratio of water, aldehyde and acetone constant, we find that the enamine formation from the first-order to proline pathway dominates when the concentration of proline is low ( 1.0 M) excess water is expected to decrease %ee. Side reactivity, including aldol condensation, acetone self-aldolization, oxazolidinone formation and azomethine and 1-oxapyrrolizidine formation were all considered in our kinetic model but shown to have a negligible effect (

Radical polymerization with reversible addition‐fragmentation chain transfer (RAFT polymerization) has been successfully applied to generate polymers of well‐defined architecture. For RAFT polymerization a source of radicals is required. Recent work has demonstrated that for minimal side‐reactions and high spatio‐temporal control these should be formed directly from the RAFT agent or macroRAFT agent (usually carbonothiosulfanyl compounds) thermally, photochemically or by electrochemical reduction. In this work, we investigated low‐energy electron attachment to a common RAFT agent (cyanomethyl benzodithioate), and, for comparison, a simple carbonothioylsulfanyl compound (dimethyl trithiocarbonate, DMTTC) in the gas phase by means of mass spectrometry as well as quantum chemical calculations. We observe for both compounds that specific cleavage of the C−S bond is induced upon low‐energy electron attachment at electron energies close to zero eV. This applies even in the case of a poor homolytic leaving group (.CH3 in DMTTC). All other dissociation reactions found at higher electron energies are much less abundant. The present results show a high control of the chemical reactions induced by electron attachment., Electron attachment leads to the efficient dissociation of carbonothioylsulfanyl molecules which are relevant for Reversible Addition‐Fragmentation chain Transfer (RAFT) polymerization. We show that the preferred C−S bond cleavage can be initiated by an electron with almost no kinetic energy, in contrast to other dissociation reactions. This feature leads to a pronounced control of bond dissociation upon electron attachment.

A simple nonphotochemical procedure is reported for Cu(I)-catalyzed C-N coupling of aliphatic halides with amines and amides. The process is loosely based on the Goldberg reaction but takes place readily at room temperature. It uses Cu(I)Br, a commonly used and inexpensive atom transfer radical polymerization precatalyst, along with the cheap ligand N,N,N',N″,N″-pentamethyldiethylenetriamine, to activate the R-X bond of the substrate via inner-sphere electron transfer. The procedure brings about productive C-N bond formation between a range of alkyl halide substrates with heterocyclic aromatic amines and amides. The mechanism of the coupling step, which was elucidated through application of computational methods, proceeds via a unique Cu(I) → Cu(II) → Cu(III) → Cu(I) catalytic cycle, involving (a) inner-sphere electron transfer from Cu(I) to the alkyl halide to generate the alkyl radical; (b) successive coordination of the N-nucleophile and the radical to Cu(II); and finally reductive elimination. In the absence of a nucleophile, debrominative homocoupling of the alkyl halide occurs. Control experiments rule out SN-type mechanisms for C-N bond formation.

Density functional theory (DFT) has been employed in predicting the enantioselectivity of the aldol reaction between acetone and p-nitrobenzaldehyde catalyzed by proline and its derivatives Me2bdc-Pro (bdc = 1,4-benzenedicarboxylate) and Me2bpdc-Pro (bpdc = 4,4'-biphenyldicarboxylate). For each catalyst, our computationally predicted values at the M062X/6-31+G(d) level of theory with the SMD solvent model are in excellent agreement with experimental results reported in the literature. Electron-donating and electron-withdrawing groups (viz., SO3-, NMe2, SO3H, and NMe3+) were installed at the C4 position of the proline-based catalysts to study the impact of electrostatic effects on stereoselectivity. The electron-donating groups decrease and even invert the enantioselectivity, while the electron-withdrawing ones increase it. Enantiomeric excesses in the range of 49-71 and 59-68% are predicted for Me2bdc-Pro and Me2bpdc-Pro catalysts with the electron-withdrawing SO3H and NMe3+ installed respectively, values much higher than those of the corresponding unmodified catalysts. More interestingly, enantiomeric excesses decrease and, in the case of SO3-, are even inverted in favor of the other enantiomer when the electron-donating groups are installed. These results highlight the importance of electrostatic effects, and polar effects more generally, in optimal organocatalyst design for stereoselective C-C bond-forming reactions.

Diene-transmissive hetero-Diels-Alder sequences involving carbonyl dienophiles are reported for the first time. High enantioselectivities are achieved in the reaction of phenylglyoxal with a broad range of dendralene structures, through the optimization of a Pd

An expanded pincer ligand tBu-PONNOP (2,7-bis(di-tert-butylphosphinito)-1,8-naphthyridine) has been synthesised and its coordination to coinage metals has been studied. Bimetallic complexes were produced with metal halide salts of the type [M2X2(tBu-PONNOP)] (X = Cl, M = Au, Ag, Cu; X = I, M = Cu) with a varying degree of interaction with the naphthyridyl backbone in the order Au < Ag < Cu. The salts [Ag2(tBu-PONNOP)2][BArF4]2 (ArF = 3,5-C6H3(CF3)2) and [Ag2(NCMe)2(tBu-PONNOP)]X2 (X = BArF4, PF6) were prepared, which may serve as a source of tBu-PONNOP via transmetallation.

Microplastics (MPs) pollution has been recognized as a threat to sustainable fisheries due to the risks of MPs contamination in the process of feed production and susceptibility of fish to ingest MPs from the aquatic environment. In this study, we applied comprehensive approaches to investigate the impacts of polyethylene microplastics (PE-MPs) on juvenile genetically improved farmed tilapia (GIFT, Oreochromis niloticus) through 9-week dietary exposure based on growth performance, gut microbiota, liver metabolism, and gene expressions in brain and liver tissues. Dietary exposure to two kinds of PE-MPs with different median size (27 μm and 63 μm, respectively) concentration-dependently decreased weight gain (WG), while increased feed conversion ratio (FCR) and hepatosomatic index (HSI) of the tilapia. Dietary administration of PE-MPs also significantly reduced the activities of intestinal protease and amylase. PE-MPs particles of the larger size groups (63 μm) were mainly detected in feces, but those of the smaller ones (27 μm) tended to be accumulated in intestine. PE-MPs ingestion resulted in the alteration of gut microbiota composition, with Fusobacteria, Verrucomicrobia and Firmicutes as the overrepresented bacterial taxa. Metabolomic assays of liver samples in fish fed the diets containing 8 % of PE-MPs revealed the particle size-specific variations in composition of differential metabolites and metabolism pathways such as amino acid and glycerophospholipid metabolism. Gene expressions of brain and liver samples were analyzed by RNA-seq. Photoperiodism and circadian rhythm were the representative biological processes enriched for the differentially expressed genes (DEGs) identified from the brain. Citrate cycle (TCA cycle) was the most enriched pathway revealed by a joint transcriptomic and metabolic pathway analysis for the liver, followed by propanoate and pyruvate metabolism. Furthermore, an integration analysis of the gut microbiome and liver transcriptome data identified significant associations between several pathogenic bacteria taxa and immune pathways. Our findings demonstrated that the sizes and concentrations of PE-MPs are critically related to their toxic impacts on microbiota community, metabolism, gene expressions and thus fish growth.

cis-1,2-Dihydrocatechols 5 (X = Me and Cl), which are available in the homochiral form through the whole-cell biotransformation of toluene and chlorobenzene, respectively, undergo Diels–Alder cyclo...

A simple nonphotochemical procedure is reported for Cu(I)-catalyzed C-N coupling of aliphatic halides with amines and amides. The process is loosely based on the Goldberg reaction but takes place readily at room temperature. It uses Cu(I)Br, a commonly used and inexpensive atom transfer radical polymerization precatalyst, along with the cheap ligand

Objective We sought to compare the angiographic and clinical outcomes of drug-coated balloon (DCB) with distal embolic protection devices (EPDs) versus bare metal stent (BMS) without EPD in the treatment of symptomatic vertebral artery origin stenosis (VAOS). Methods Between January 2017 and December 2018, a prospective randomized trial was conducted involving 95 patients with symptomatic VAOS randomly assigned to treatment with DCB + EPD (n = 49) or BMS without EPD (n = 46). Target vessel restenosis (RS) >50% detected by computed tomography angiography was the primary endpoint. Technical success, clinical success, and signal intensity abnormalities on diffusion-weighted imaging within 3 days after operation were compared. Results The 30-day technical success rate was 93.9% for DCB group versus 95.7% for the BMS group (P = 0.094). Diffusion-weighted imaging within 3 days postoperative showed asymptomatic embolization in 2 (4.1%) patients in the DCB group and 9 (19.6%) patients in the BMS group (P = 0.004). At a mean 16-month follow-up, the clinical success rate was 89.8% for the DCB group versus 91.3% (42/46) for the BMS group (P = 0.125). The RS was seen in 5/49 (10.2%) in the DCB group and 6/46 (13.0%) in the BMS group (P = 0.082). Target vessel revascularization was performed in 4 (8.7%) BMS group versus 3 (6.1%) in the DCB group (P = 0.091). Conclusions DCB with EPD in the treatment of symptomatic VAOS is technically feasible and safe and significantly reduced thromboembolic events on imaging when compared with BMS without EPD. There was no significant difference between the 2 groups in the rate of RS during 12 months after surgery.

In our study, patients who had a second delivery were categorised into the following 4 groups. Pelvic floor ultrasound data were compared during the 6th week after the second delivery. The incidence of cystoceles was highest in group A and lowest in group D. In addition, groups A and B had a higher rate of rectoceles or perineum descent. Similarly, the areas of the levator hiatus were higher in Groups A and B during Valsalva manoeuvres. The area of the levator hiatus from the resting state to the Valsalva manoeuvre effect had the greatest change in Group A. A comparison of the PR thickening rates among the four groups did not reveal significant differences. All second delivery methods can cause varying degrees of pelvic organ prolapse and decreased pelvic floor function; however, vaginal delivery as the second delivery mode may have a more significant effect in Chinese women.Impact StatementWhat is already known on this subject? Different modes of delivery have significantly different effects on female pelvic floor function. Pregnancy beyond 35 weeks of gestation has an effect on female pelvic floor function, irrespective of the mode of delivery.What do the results of this study add? This study analysed the impact of different delivery modes on Chinese female pelvic floor function. Parous women who underwent different modes of second delivery all demonstrated different degrees of pelvic organ prolapse, as well as pelvic floor function decline.What are the implications of these findings for clinical practice and/or further research? Our study will provide basic research of Chinese female pelvic floor function after a second delivery, which will be of clinical significance around the world, as well as in China. China will keep promoting further delivery as the aging population is increasing. If the developing countries want to promote the second delivery around the women, they have basic research and data to instruct the females. What is already known on this subject? Different modes of delivery have significantly different effects on female pelvic floor function. Pregnancy beyond 35 weeks of gestation has an effect on female pelvic floor function, irrespective of the mode of delivery. What do the results of this study add? This study analysed the impact of different delivery modes on Chinese female pelvic floor function. Parous women who underwent different modes of second delivery all demonstrated different degrees of pelvic organ prolapse, as well as pelvic floor function decline. What are the implications of these findings for clinical practice and/or further research? Our study will provide basic research of Chinese female pelvic floor function after a second delivery, which will be of clinical significance around the world, as well as in China. China will keep promoting further delivery as the aging population is increasing. If the developing countries want to promote the second delivery around the women, they have basic research and data to instruct the females.

A test set 264 nucleophilic substitution reactions was studied via accurate quantum chemical reactions to establish the relative preferences for SN1 versus SN2 mechanisms. In low polar solvents, reactions involving anionic nucleophiles and leaving groups favored SN2 pathways. In contrast, SN1 is preferred for those reactions involving neutral nucleophiles and leaving groups except where the carbocation intermediates are exceptionally unstable. For neutral nucleophiles and anionic leaving groups, SN2 is generally preferred over SN1 except for exceptionally stable carbocation intermediates. On the basis of these studies, candidate reactions for which distinct SN1 or SN2 preferences could be reversed by electric fields were selected. As proof of concept, the SN1/SN2 preferences for the reaction of tBu-triflate with pyridine (SN2 to SN1) and with piperidine (SN1 to SN2) were switched by both charged functional groups and point charges (i.e., electric fields) along the reaction axis, with a positive charge on the nucleophile side favoring SN1 and a negative charge favoring SN2 for these reactions.

The evolution of gaseous products is a feature common to several electrochemical processes, often resulting in bubbles adhering to the electrode’s surface. Adherent bubbles reduce the electrode active area, and are therefore generally treated as electrochemically inert entities. Here, we show that this general assumption does not hold for gas bubbles masking anodes operating in water. By means of imaging electrochemiluminescent systems, and by studying the anisotropy of polymer growth around bubbles, we demonstrate that gas cavities adhering to an electrode surface initiate the oxidation of water-soluble species more effectively than electrode areas free of bubbles. The corona of a bubble accumulates hydroxide anions, unbalanced by cations, a phenomenon which causes the oxidation of hydroxide ions to hydroxyl radicals to occur at potentials at least 0.7 V below redox tabled values. The downhill shift of the hydroxide oxidation at the corona of the bubble is likely to be a general mechanism involved in the initiation of heterogeneous electrochemical reactions in water, and could be harnessed in chemical synthesis., Gas bubbles forming on the surface of an electrode, a phenomenon common to several industrial electrolytic processes, are usually perceived as inert, passivating entities. Here, the authors show that that this general assumption does not hold for gas bubbles masking anodes operating in water.

International audience; Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the cornerstone of atmospheric CO2 fixation by the biosphere. It catalyzes the addition of CO2 onto enolized ribulose 1,5-bisphosphate (RuBP), producing 3-phosphoglycerate which is then converted to sugars. The major problem of this reaction is competitive O-2 addition, which forms a phosphorylated product (2-phosphoglycolate) that must be recycled by a series of biochemical reactions (photorespiratory metabolism). However, the way the enzyme activates O-2 is still unknown. Here, we used isotope effects (with H-2, Mg-25, and O-18) to monitor O-2 activation and assess the influence of outer sphere atoms, in two Rubisco forms of contrasted O-2/CO2 selectivity. Neither the Rubisco form nor the use of solvent D2O and deuterated RuBP changed the O-16/O-18 isotope effect of O-2 addition, in clear contrast with the C-12/C-13 isotope effect of CO2 addition. Furthermore, substitution of light magnesium (Mg-24) by heavy, nuclear magnetic Mg-25 had no effect on O-2 addition. Therefore, outer sphere protons have no influence on the reaction and direct radical chemistry (intersystem crossing with triplet O-2) does not seem to be involved in O-2 activation. Computations indicate that the reduction potential of enolized RuBP (near 0.49 V) is compatible with superoxide (O-2(center dot-)) production, must be insensitive to deuteration, and yields a predicted O-16/O-18 isotope effect and energy barrier close to observed values. Overall, O-2 undergoes single electron transfer to form short-lived superoxide, which then recombines to form a peroxide intermediate.

Despite their apparent similarity, framework materials based on tetraphenylmethane and tetraphenylsilane building blocks often have quite different structures and topologies. Herein, we describe a new silicon tetraamidinium compound and use it to prepare crystalline hydrogen bonded frameworks with carboxylate anions in water. The silicon-containing frameworks are compared with those prepared from the analogous carbon tetraamidinium: when biphenyldicarboxylate or tetrakis(4-carboxyphenyl)methane anions were used similar channel-containing networks are observed for both the silicon and carbon tetraamidinium. When terephthalate or bicarbonate anions were used, different products form. Insights into possible reasons for the different products are provided by a survey of the Cambridge Structural Database and quantum chemical calculations, both of which indicate that, contrary to expectations, tetraphenylsilane derivatives have less geometrical flexibility than tetraphenylmethane derivatives, i.e. they are less able to distort away from ideal tetrahedral bond angles.

Despite their apparent similarity, framework materials based on tetraphenylmethane and tetraphenylsilane building blocks often have quite different structures and topologies. Herein, we describe a new silicon tetraamidinium compound and use it to prepare crystalline hydrogen bonded frameworks with carboxylate anions in water. The silicon-containing frameworks are compared with those prepared from the analogous carbon tetraamidinium: when biphenyldicarboxylate or tetrakis(4-carboxyphenyl)methane anions were used similar channel-containing networks are observed for both the silicon and carbon tetraamidinium. When terephthalate or bicarbonate anions were used, different products form. Insights into possible reasons for the different products are provided by a survey of the Cambridge Structural Database and quantum chemical calculations, both of which indicate that, contrary to expectations, tetraphenylsilane derivatives have less geometrical flexibility than tetraphenylmethane derivatives, i.e. they are less able to distort away from ideal tetrahedral bond angles.

Despite their apparent similarity, framework materials based on tetraphenylmethane and tetraphenylsilane building blocks often have quite different structures and topologies. Herein, we describe a new silicon tetraamidinium compound and use it to prepare crystalline hydrogen bonded frameworks with carboxylate anions in water. The silicon-containing frameworks are compared with those prepared from the analogous carbon tetraamidinium: when biphenyldicarboxylate or tetrakis(4-carboxyphenyl)methane anions were used similar channel-containing networks are observed for both the silicon and carbon tetraamidinium. When terephthalate or bicarbonate anions were used, different products form. Insights into possible reasons for the different products are provided by a survey of the Cambridge Structural Database and quantum chemical calculations, both of which indicate that, contrary to expectations, tetraphenylsilane derivatives have less geometrical flexibility than tetraphenylmethane derivatives, that is, they are less able to distort away from ideal tetrahedral bond angles.

11 pags., 8 figs., 1 tab., The relatively weak London dispersion forces are the only interactions that could cause aggregation between simple aromatic molecules. The use of molecular dynamics and high-levelab initiocomputer simulations has been used to describe the aggregation and interactions between molecular systems containing benzene, naphthalene and anthracene. Mixtures containing one type of molecule (homogenous) and more than one type of molecule (heterogenous) were considered. Our results indicate that as molecular weight increases so does the temperature at which aggregation will occur. In all simulations, the mechanism of aggregation is through small clusters coalescing into larger clusters. The structural analysis of the molecules within the clusters reveals that benzene will orient itself in T-shaped and parallel displaced configurations. Molecules of anthracene prefer to orient themselves in a similar manner to a bulk crystal with no T-shaped configuration observed. The aggregation of these aromatic molecules is discussed in the context of astrochemistry with particular reference to the dust formation region around stars., NAMD was developed by the Theoretical and Computational Biophysics Group in the Beckman Institute for Advanced Science and Technology at the University of Illinois at UrbanaChampaign. This work was in part supported by resources provided by the Pawsey Supercomputing Centre with funding from the Australian Government and the Government of Western Australia, with the assistance of computational resources from the Pople high-performance computing cluster of the Faculty of Science at the University of Western Australia and with the assistance of resources from the National Computational Infrastructure (NCI), which is supported by the Australian Government. AK gratefully acknowledges an Australian Research Council (ARC) Future Fellowship (Project No. FT170100373). I. S. M. fellowship is funded by Australian Research Council (No. FT140100191). I. C. acknowledges funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007– 2013)/ERC2013-SyG, Grant Agreement No. 610256 NANOCOSMOS. DT acknowledges MEAE and MESRI for the financial support.

Pyrolysis of variously pretreated or untreated samples of chitin (1) and certain congeners at 150-350 °C afforded a range of platform molecules, as exemplified by compounds 4, 5, 6, 8, 12 and 13. All of these products have been fully characterized, including by single-crystal X-ray analysis. Pathways for the formation of them are proposed and theoretical studies of certain aspects of these described.

Reversible deactivation radical polymerization of vinyl chloride (VC) by methyl (ethoxycarbonothioyl)sulfanyl acetate (MEA)-mediated macromolecular design via the interchange of xanthate (MADIX) po...