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Journal of the American Chemical Society

Hao Li, Feng Qin, Zhiping Yang, Ximin Cui, Jianfang Wang, Lizhi Zhang
Selective organic transformation under mild conditions constitutes a challenge in green chemistry, especially for alcohol oxidation, which typically requires environmentally unfriendly oxidants. Here, we report a new plasmonic catalyst of Au supported on BiOCl containing oxygen vacancies. It photocatalyzes selective benzyl alcohol oxidation with O2 under visible light through synergistic action of plasmonic hot electrons and holes. Oxygen vacancies on BiOCl facilitate the trapping and transfer of plasmonic hot electrons to adsorbed O2, producing •O2(‒) radicals, while plasmonic hot holes remaining on the Au surface mildly oxidize benzyl alcohol to corresponding carbon-centered radicals...
February 17, 2017: Journal of the American Chemical Society
Guoqiang Wang, Jia Cao, Liuzhou Gao, Wenxin Chen, Wenhao Huang, Xu Cheng, Shuhua Li
Density functional theory investigations revealed that the pyridine-boryl radical generated in situ using 4-cyanopyridine and bis(pinacolato)diboron could be used as a bifunctional "reagent", which serves as not only a pyridine precursor but also a boryl radical. With the unique reactivity of such radicals, 4-substituted pyridine derivatives could be synthesized using α, β-unsaturated ketones and 4-cyanopyridine via a novel radical addition/C-C coupling mechanism. Several controlled experiments were conducted to provide supportive evidence for the proposed mechanism...
February 17, 2017: Journal of the American Chemical Society
Jeff Van Raden, Shayan Louie, Lev N Zakharov, Ramesh Jasti
Owing to their unique cyclic architectures, tunable electronic properties, and supramolecular chemistries, cycloparaphenylenes (CPPs) have the potential to act as a new class of ligands for coordination cages, metal-organic frameworks (MOFs), as well as small-molecule transition-metal complexes. However, currently there is no general strategy to coordinate the cyclic framework to a variety of metal centers. We report here a general and scalable synthetic strategy to embed 2,2'-bipyridine units into the backbone of CPPs...
February 17, 2017: Journal of the American Chemical Society
Shaozhong Ge, Rebecca A Green, John F Hartwig
No abstract text is available yet for this article.
February 17, 2017: Journal of the American Chemical Society
Li-Qiang Xie, Liang Chen, Zi-Ang Nan, Hai-Xin Lin, Tan Wang, Dongping Zhan, Jia-Wei Yan, Bing-Wei Mao, Zhong-Qun Tian
The spontaneous α-to-δ phase transition of the Formamidinium-based (FA) lead halide perovskite hinders its large scale application in solar cells. Though this phase transition can be inhibited by alloying with Methylammonium-based (MA) perovskite, the underlying mechanism is largely unexplored. In this communication, we grow high quality mixed cations and halides perovskite single crystals (FAPbI3)1-x(MAPbBr3)x to understand the principles for maintaining pure perovskite phase, which is essential to device optimization...
February 17, 2017: Journal of the American Chemical Society
Marco Dunwell, Qi Lu, Jeffrey M Heyes, Jonathan Rosen, Jingguang G Chen, Yushan Yan, Feng Jiao, Bingjun Xu
Much effort has been devoted in the development of efficient catalysts for electrochemical reduction of CO2. Molecular level understanding of electrode-mediated process, particularly the role of bicarbonate in increasing CO2 reduction rates, is still lacking due to the difficulty of directly probing the electrochemical interface. We developed a protocol to observe normally invisible reaction intermediates with a surface enhanced spectroscopy by applying square-wave potential profiles. Further, we demonstrate that bicarbonate, through equilibrium exchange with dissolved CO2, rather than the supplied CO2, is the primary source of carbon in the CO formed at the Au electrode by a combination of in-situ spectroscopic, isotopic labeling, and mass spectroscopic investigations...
February 17, 2017: Journal of the American Chemical Society
Ellen Benn, Bernard Gaskey, Jonah D Erlebacher
Electroreduction of small molecules in aqueous solution often competes with the hydrogen evolution reaction (HER), especially if the reaction is driven even moderately hard using a large overpotential. Here, the oxygen reduction reaction (ORR) was studied under proton diffusion-limited conditions in slightly acidic electrolytes - a model system to study the relative transport kinetics of protons and reactants to an electrocatalyst and the relationship between transport and catalytic performance. Using dealloyed nanoporous nickel-platinum (np-NiPt) electrodes, we find the hydrogen evolution reaction can be completely suppressed even at high overpotentials (-400 mV vs...
February 17, 2017: Journal of the American Chemical Society
Ali Nazemi, Xiaoming He, Liam R MacFarlane, Robert L Harniman, Ming-Siao Hsiao, Mitchell A Winnik, Charl F J Faul, Ian Manners
Rectangular platelets formed by the self-assembly of block copolymers in selective solvents are of interest for a range of applications. Recently we showed that the seeded growth of crystallizable blends of a block copolymer and homopolymer yields well-defined, low dispersity examples of these two-dimensional (2D) structures. The key feature was the use of the same crystallizable polymer segment in the seed and blend components to enable an efficient homoepitaxial growth process. Herein we demonstrate that this 2D crystallization-driven self-assembly approach can be extended to heteropitaxial growth by the use of different crystallizable polymers with compatible crystal structures...
February 17, 2017: Journal of the American Chemical Society
Wenchao Zhang, Jianfeng Mao, Sean Li, Zhixin Chen, Zaiping Guo
Potassium-ion batteries (PIBs) are interesting as one of the alternative metal-ion battery systems to lithium-ion batteries (LIBs) due to the abundance and low cost of potassium. We have herein investigated Sn4P3/C composite as a novel anode material for PIBs. The electrode delivered a reversible capacity of 384.8 mA h g-1 at 50 mA g-1 and a good rate capability of 221.9 mA h g-1, even at 1 A g-1. Its electrochemical performance is better than any anode material reported so far for PIBs. It was also found that the Sn4P3/C electrode displays a discharge potential plateau of 0...
February 17, 2017: Journal of the American Chemical Society
Lianqian Wu, Fei Wang, Xiaolong Wan, Dinghai Wang, Pinhong Chen, Guosheng Liu
A novel asymmetric radical trifluoromethyl-arylation of alkenes has been developed, which provides an efficient approach to access chiral CF3-containing 1,1-diarylmethane derivatives with good to excellent enantioselectivity. Various vinyl arenes and aryl boronic acids are compatible with these conditions. The utility of the method is demonstrated by accessing modified bioactive molecules.
February 17, 2017: Journal of the American Chemical Society
Riccardo Alessandri, Jaakko J Uusitalo, Alex H De Vries, Remco W A Havenith, Siewert J Marrink
Control over the morphology of the active layer of bulk heterojunction (BHJ) organic solar cells is paramount to achieve high efficiency devices. However, no method currently available can predict morphologies for a novel donor:acceptor blend. An approach which allows to reach relevant length scales, retain chemical specificity, mimic experimental fabrication conditions, and which is suited for high-throughput schemes has been proven challenging to find. Here, we propose a method to generate atom-resolved morphologies of BHJs which conforms to these requirements...
February 17, 2017: Journal of the American Chemical Society
Jian He, Qian Shao, Qingfeng Wu, Jin-Quan Yu
Pd(II)-catalyzed enantioselective borylation of C(sp3)-H bonds has been realized for the first time using chiral acetyl-protected aminomethyl oxazolines ligands. This reaction is compatible with carbocyclic amides containing α-tertiary as well as α-quaternary carbon centers. The chiral β-borylated amides are useful synthons for the synthesis of chiral β-hydroxylated, β-fluorinated, and β-arylated carboxylic acids.
February 17, 2017: Journal of the American Chemical Society
Bing An, Jingzheng Zhang, Kang Cheng, Pengfei Ji, Cheng Wang, Wenbin Lin
The interfaces of Cu/ZnO and Cu/ZrO2 play vital roles in the hydrogenation of CO2 to methanol by these composite catalysts. Surface structural reorganization and particle growth during catalysis deleteriously reduce these active interfaces, diminishing both catalytic activities and MeOH selectivities. Here we report the use of pre-assembled bpy and Zr6(μ3-O)4(μ3-OH)4 sites in UiO-bpy metal-organic frameworks (MOFs) to anchor ultrasmall Cu/ZnOx nanoparticles, thus preventing the agglomeration of Cu NPs and phase separation between Cu and ZnOx in MOF cavity-confined Cu/ZnOx nanoparticles...
February 17, 2017: Journal of the American Chemical Society
Thanh Huong Pham, Joel S Olsson, Patric Jannasch
The development of cationic polymers for anion-exchange membranes (AEMs) with high alkaline stability and conductivity is a considerable challenge in materials chemistry. In response, we here present the synthesis and properties of N-spirocyclic quaternary ammonium ionenes (spiro-ionenes) containing 5- and 6-membered rings fused by central nitrogen cations. High-molecular weight and film-forming spiro-ionenes are successfully synthesized in cyclo-polycondensations of tetrakis(bromomethyl)benzene and dipiperidines under mild conditions...
February 17, 2017: Journal of the American Chemical Society
Qi-Liang Yang, Yi-Qian Li, Cong Ma, Ping Fang, Xiu-Jie Zhang, Tian-Sheng Mei
Palladium-catalyzed C-H activation/C-O bond-forming reactions have emerged as attractive tools for organic synthesis. Typically, these reactions require strong chemical oxidants, which convert organopalladium(II) intermediates into the Pd(III) or Pd(IV) oxidation state to promote otherwise challenging C-O reductive elimination. However, previously reported oxidants possess significant disadvantages, including poor atom economy, high cost, and the formation of undesired byproducts. To overcome these issues, we report an electrochemical strategy that takes advantage of anodic oxidation of Pd(II) to induce selective C-O reductive elimination with a variety of oxyanion coupling partners...
February 17, 2017: Journal of the American Chemical Society
Emiko Kazuma, Jaehoon Jung, Hiromu Ueba, Michael Trenary, Yousoo Kim
We demonstrate molecular photodissociation on single-crystalline metal substrates, driven by visible-light irradiation. The visible-light-induced photodissociation on metal substrates has long been thought to never occur, either because visible-light energy is much smaller than the optical energy gap between the frontier electronic states of the molecule or because the molecular excited states have short lifetimes due to the strong hybridization between the adsorbate molecular orbitals (MOs) and metal substrate...
February 17, 2017: Journal of the American Chemical Society
Jonathan Rittle, Jonas C Peters
Fe-mediated biological nitrogen fixation is thought to proceed via either a sequence of proton and electron transfer steps, concerted H atom transfer steps, or some combination thereof. Regardless of the specifics and whether the intimate mechanism for N2-to-NH3 conversion involves a distal pathway, an alternating pathway, or some hybrid of these limiting scenarios, Fe-NxHy intermediates are implicated that feature reactive N-H bonds. Thermodynamic knowledge of the N-H bond strengths of such species is scant, and is especially difficult to obtain for the most reactive early stage candidate intermediates (e...
February 17, 2017: Journal of the American Chemical Society
Shan Gao, Bingchuan Gu, Xingchen Jiao, Yongfu Sun, Xiaolong Zu, Fan Yang, Wenguang Zhu, Chengming Wang, Zimou Feng, Bangjiao Ye, Yi Xie
Unearthing an ideal model for disclosing the role of defect sites in solar CO2 reduction remains a great challenge. Here, freestanding gram-scale single-unit-cell o-BiVO4 layers are successfully synthesized for the first time. Positron annihilation spectrometry and X-ray fluorescence unveil their distinct vanadium vacancy concentrations. Density functional calculations reveal the introduction of vanadium vacancies brings a new defect level and higher hole concentration near Fermi level, resulting in increased photoabsorption and superior electronic conductivity...
February 16, 2017: Journal of the American Chemical Society
Sourabh Mishra, Ji Liu, Aaron Aponick
By the nature of its structure, the 5-membered chiral biaryl heterocyclic scaffold represents a departure from 6-membered P,N-ligands that facilitates tuning and enables ligand evolution to address issues of selectivity and reactivity. In this vein, the Cu-catalyzed enantioselective conjugate alkynylation of Meldrum's acid acceptors is reported using Me-StackPhos. Enabled by this new ligand, the reaction tolerates a wide range of alkynes furnishing the products in high yields and excellent enantioselectivity...
February 16, 2017: Journal of the American Chemical Society
Resham J Banga, Brian Meckes, Suguna P Narayan, Anthony J Sprangers, SonBinh T Nguyen, Chad A Mirkin
A one-pot synthesis of micellar spherical nucleic acid (SNA) nanostructures using Pluronic F127 as a thermoresponsive template is reported. These novel constructs are synthesized in a chemically straightforward process that involves intercalation of the lipid tails of DNA amphiphiles (CpG motifs for TLR-9 stimulation) into the hydrophobic regions of Pluronic F127 micelles followed by chemical cross-linking and subsequent removal of non-crosslinked structures. The dense nucleic acid shell of the resulting cross-linked micellar SNA enhances their stability in physiological media and facilitates their rapid cellular internalization making them effective TLR-9 immunomodulatory agents...
February 16, 2017: Journal of the American Chemical Society
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