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Chemistry: a European Journal

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https://www.readbyqxmd.com/read/28929551/pd-c-catalysed-aminocarbonylation-of-aryl-iodides-with-anthranils-in-water-using-mo-co-6-as-the-co-source
#1
Xiao-Feng Wu, Zechao Wang, Zhiping Yin
A convenient procedure for the synthesis of N-(2-carbonylaryl)benzamides has been developed. Through Pd/C-catalysed aminocarbonylation of anthranils with various hindered and functionalized aryl iodides, the desired amides were afforded in moderate to good yields. The protocol is advantageous due to the recyclable Pd/C catalyst, safe Mo(CO)6 as the solid CO source, and environmentally benign water as solvent. No inert atmosphere protection is needed.
September 20, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28929599/rutile-tio2-mesocrystals-as-a-novel-sulfur-host-for-high-performance-lithium-sulfur-batteries
#2
Qingqing Sun, Kaixiang Chen, Yubin Liu, Yafeng Li, Mingdeng Wei
Although Lithium-sulfur (Li-S) batteries are one of the most promising rechargeable batteries in energy storage devices, the poor cycling performance of Li-S batteries restricts their potential application. The polar materials can improve the cycling stability due to their inherent strong chemical interaction with polysulfides. Herein, a novel rutile TiO2 mesocrystals (RTMs) was employed as the host of sulfur in Li-S, displaying a stable cycling performance with a capacity retention of 64% and a small average capacity decay rate of 0...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28929548/an-fe-iii-aza-macrocyclic-complex-as-ph-tunable-catholyte-and-anolyte-for-redox-flow-battery-applications
#3
Pavel B Tsitovich, Anjula M Kosswattaarachchi, Matthew R Crawley, Timothy Y Tittiris, Timoth R Cook, Janet Ruth Morrow
A reversible Fe3+/Fe2+ redox couple of an aza-macrocyclic complex is evaluated as an electrolyte with a pH-tunable potential range for aqueous redox-flow batteries (RFBs). The Fe(III) complex is formed by 1,4,7-triazacyclononane (TACN) appended with three 2-methyl-imidazole donors, denoted as Fe(Tim). This complex exhibits pH-sensitive redox couples that span E1/2(Fe3+/Fe2+)=317 to -270 mV vs. NHE at pH 3.3 and pH 12.8, respectively. The 590 mV shift in potential and kinetic inertness are driven by ionization of the imidazoles at various pH values...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28929536/mixed-phthalocyanine-porphyrin-fused-conjugated-pentameric-nanoarrays
#4
Jianzhuang Jiang, Yuehong Zhang, Zheng Xue, Dongdong Qi, Kang Wang, Huibiao Liu
The largest phthalocyanine-porphyrin-fused pentameric molecular arrays have been synthesized and spectroscopically characterized. The saddled molecular conformation revealed for the pentamer by DFT-D3 calculation in combination with the bulky peripheral substituents precludes effective face-to-face π-π intermolecular interaction. As a consequence, intermolecular C-H…π interactions together with the ubiquitous dispersion force arrays help to self-assemble the representative metal-free pentameric molecules into the three-dimensional supramolecular structures with nanaorod morphology in CHCl3 and n-butanol...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28926133/synthesis-of-thiophene-based-optical-ligands-that-selectively-detect-tau-pathology-in-alzheimer%C3%A2-s-disease
#5
Peter Nilsson, Hamid Shirani, Hanna Appelqvist, Marcus Bäck, Therese Klingstedt, Nigel Cairns
The accumulation of protein aggregates is associated with many devastating neurodegenerative diseases and the development of molecular ligands able to detect these pathological hallmarks is essential. Here, we report the synthesis of thiophene based optical ligands, denoted bi-thiophene-vinyl-benzothiazoles (bTVBTs) that can be utilized for selective assignment of tau aggregates in brain tissue with Alzheimer´s disease (AD) pathology. The ability of the ligands to selectively distinguish tau deposits from the other AD associated pathological hallmark, senile plaques consisting of aggregated amyloid-β (Aβ) peptide, were reduced when the chemical composition of the ligands were altered, verifying that specific molecular interactions between the ligands and the aggregates are necessary for the selective detection of tau deposits...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28926128/copper-catalysed-aminoboration-of-vinylarenes-with-hydroxylamine-esters-a-computational-mechanistic-study
#6
Sven Tobisch
This first comprehensive computational study of the copper-mediated formal aminoboration utilising an electrophilic strategy has identified the most accessible pathway for the productive catalysis. The mechanistic picture derived from smooth energy profiles acquired by employing a reliable computational protocol applied to a realistic catalyst model conforms to all available experimental data. The high degree of chemo- and stereoselectivity achieved in syn-borylcupration and Umpolung electrophilic amination is instrumental to the exclusive generation of the (syn)-beta-aminoalkylborane product...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28925521/quasi-emulsion-confined-synthesis-of-edge-rich-ultrathin-mos2-nanosheets-graphene-hybrid-for-enhanced-hydrogen-evolution
#7
Xuying Yin, Ya Yan, Mao Miao, Ke Zhan, Pingwei Li, Junhe Yang, Bin Zhao, Bao Yu Xia
Hydrogen with high purity produced by water splitting is considered as one of the most promising technology to replace the traditional fossil fuels. Developing highly efficient electrocatalysts towards hydrogen evolution is vital for the realization of H2 generation in large scale. With assistance of glycerol, we report herein a facile solvothermal process to synthesize edge-rich ultrathin MoS2/RGO composites. The introduction of glycerol plays an important role in the formation of such an interesting structure...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28925520/rational-design-of-bifunctional-2-fold-interpenetrated-zn-ii-metal-organic-framework-for-selective-adsorption-of-co2-and-efficient-aqueous-phase-sensing-of-2-4-6-trinitrophenol
#8
C M Nagaraja, Sandeep Dhankhar, Nayuesh Sharma, Sandeep Kumar, Dhilip Kumar
A bifunctional, microporous Zn(II) metal-organic framework, [Zn2(NH2BDC)2(dpNDI)]n (MOF1) (where, NH2BDC =2-aminoterephthalic acid, dpNDI =N,N'-di(4-pyridyl)-1,4,5,8-naphthalenediimide) has been synthesized solvothermally. MOF1 shows a 2-fold interpenetrated, 3D pillar-layered framework structure composed of two types of 1D channels with dimensions of ~3.80 x 16.9 Å2 and 7.49 x 17.01 Å2 decorated with pendent -NH2 group. Owing to the presence of basic functionalized pore surface, MOF1 exhibits selective adsorption of CO2 with high value of heat of adsorption (Qst = 46...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28925518/chemistry-of-peptidoglycan-in-mycobacterium-tuberculosis-life-style-an-off-the-wall-balance-of-synthesis-and-degradation
#9
Flavia Squeglia, Alessia Ruggiero, Rita Berisio
The cell wall envelope of mycobacteria is structurally distinct from that of both Gram-positive and Gram-negative bacteria. In Mycobacterium tuberculosis, this cell wall has unique structural features and plays a crucial role in drug resistance and macrophage survival under stress conditions. Peptidoglycan is the major constituent of this cell wall, with an important structural role, giving structural strength, and counteracting the osmotic pressure of the cytoplasm. Synthesis of this complex polymer takes place in three stages that occur at three different locations in the cell, from the cytoplasm to the external side of the cell membrane, where polymerization occurs...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28925516/co3o4-nanowire-arrays-toward-superior-water-oxidation-electrocatalysis-in-alkaline-media-by-surface-amorphization
#10
Xuping Sun
In this communication, we report our recent finding that the generation of amorphous Co-Bi layer on Co3O4 nanowire arrays supported on Ti mesh (Co3O4@Co-Bi NA/TM) leads to significantly boosted OER activity. The as-prepared Co3O4@Co-Bi NA/TM demands overpotential of 304 mV to drive a ge-ometrical current density of 20 mA cm-2 in 1.0 M KOH, which is 109 mV less than that for Co3O4 NA/TM, with its catalytic activity being preserved for at least 20 h. It suggests that the existence of amorphous Co-Bi layer promotes more CoOx(OH)y generation on Co3O4 surface...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28925514/a-one-step-germole-to-silole-transformation-and-a-stable-isomer-of-a-disilabenzene
#11
Thomas Müller, Crispin Reinhold, Zhaowen Dong, Jan Winkler, Henning Steinert, Marc Schmidtmann
An unusual germole-to-silole transformation is described. As key intermediates hetero-fulvenes are formed which rearrange to more stable bicyclic carbene analogues. The so-formed germylenes undergo a reductive elimination yielding elemental germanium and siloles. In contrast, the analogous silylenes are stable at ambient conditions and were identified by MS spectrometry and NMR spectroscopy supported by the results of quantum mechanical calculations. These bicyclic silylenes are stable derivatives of the global minimum of the C4Si2H6 potential energy surface...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28925104/the-nature-of-hydrated-protons-on-platinum-surface
#12
YounJoon Jung, Heon Kang, Youngsoon Kim, Chanwoo Noh
The nature of hydrated protons formed at water/metal interfaces is one of the most intriguing research questions in the field of interfacial chemistry. We prepared coadsorption layers of hydrogen and water on a Pt(111) surface in ultrahigh vacuum and studied the ionization of adsorbed hydrogen atoms to H+ ions by employing a combined experimental and theoretical approach. Spectroscopic evidence obtained by mass spectrometry and reflection absorption infrared spectroscopy as well as corresponding density functional theory calculations consistently show that adsorbed hydrogen atoms ionize into multiply hydrated proton species (H5O2+, H7O3+, and H9O4+) on the surface, rather than H3O+...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28925081/accessing-two-coordinate-zn-ii-organocations-via-nhc-coordination-synthesis-structure-and-use-as-%C3%AF-lewis-acids-in-alkene-alkyne-and-co2-hydrosilylation
#13
Samuel Dagorne, David Specklin, Frédéric Hild, Christophe Fliedel, Christophe Gourlaouen, Luis Veiros
Discrete two-coordinate Zn(II) organocations are first reported, presently of the type (NHC)Zn-R+, thanks to NHC stabilization. In preliminary reactivity studies, such entities, which are direct cationic analogues of long-known ZnR2 species, act as effective and tunable π-Lewis acid catalysts in alkene, alkyne and CO2 hydrosilylation.
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28925004/size-dependent-reactivity-of-nano-sized-neutral-manganese-oxide-clusters-toward-ethylene
#14
Jiao-Jiao Chen, Ting Zhang, Mei-Qi Zhang, Qing-Yu Liu, Xiao-Na Li, Sheng-Gui He
Neutral manganese oxide clusters Mn2NO3N+x (N = 2-22; x = -1, 0, 1) with dimensions up to a nanosize were prepared by laser ablation and reacted with C2H4 in a fast flow reactor. The size-dependent reactivity of C2H4 adsorption on these clusters was experimentally identified and the adsorption reactivity decreases generally with the increase of cluster size. Density functional theory calculations were performed to study the geometrical and electronic structures of Mn2NO3N (N = 1-6) clusters. The calculated results indicated that the coordination number and the charge distribution of the metal centers are responsible for the experimentally observed size-dependent reactivity...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28925075/understanding-the-catalytic-mechanism-and-the-nature-of-transition-state-of-an-attractive-drug-target-enzyme-shikimate-kinase-by-qm-mm-studies
#15
Jianzhuang Yao, Xia Wang, Haixia Luo, Pengfei Gu
Shikimate kinase (SK), is the fifth bacterial enzyme involved in the shikimate pathway for biosynthesis of life indispensable components, such as aromatic amino acids. Absence of shikimate pathway in human makes SK an attractive target for rational design of drug toward pathogenesis bacteria, such as Mycobacterium tuberculosis and Helicobacter pylori. However, effective inhibitor of SK (e.g., transition state analogue) is still not available in the market due to (at least partly) the lack of knowledge on the catalytic mechanism and the nature of the rate-limiting transition state...
September 18, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28925062/better-organic-ternary-memory-performance-through-self-assembled-alkyltrichlorosilane-monolayers-on-indium-tin-oxide-ito-surfaces
#16
Xiang Hou, Xue-Feng Cheng, Jin Zhou, Jing-Hui He, Qing-Feng Xu, Hua Li, Na-Jun Li, Dong-Yun Chen, Jian-Mei Lu
Recently surface engineering of the indium-tin oxide (ITO) electrode of sandwich-like organic electric memory is found to effectively improve their memory performances. However, there are few methods to modify ITO substrates. In this paper, we have successfully prepared alkyltrichlorosicane self-assembled monolayers (SAMs) on ITO substrates, and resistive random access memory devices are fabricated on these surfaces. Compared to the unmodified ITO substrates, organic molecules SA-Bu grown on these SAM-modified ITO substrates have rougher surface morphologies but smaller mosaicity...
September 18, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28925020/one-pot-synthesis-of-size-controllable-core-shell-cds-and-derivative-cds-znxcd1-xs-structures-for-dramatic-photocatalytic-hydrogen-production
#17
Shuangshuang Kai, Baojuan Xi, Yifeng Wang, Shenglin Xiong
Chalcogenide micro/nano composite structures have been attracting world-wide attention due to the enormous prospect of applications in photocatalytic hydrogen production. Well-defined micro/nanostructures, featured with predominant properties, are of extraordinary importance. Herein, we reported a facile one-pot method on synthesis of monodispersed size-controllable CdS and CdS@ZnxCd1-xS core-shell submicrospheres, which were engineered with respect to the structural conformation and size. CdS core-shell submicrospheres with different size were selectively prepared for the first time...
September 18, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28924983/synergistic-configuration-of-diols-as-br%C3%A3-nsted-bases
#18
Ye-Jin Kim, Surajit Rakshit, Geun Young Jin, Prasun Ghosh, Young Min Lee, Won-Woo Park, Yung Sam Kim, Oh-Hoon Kwon
As viscous hydroxylic organic compounds, diols are of interest for their functional molecular conformation, which is based on inter- and intramolecular hydrogen (H)-bonds. By utilising steady-state electronic and vibrational spectroscopy, time-resolved fluorescence spectroscopy, and computational analyses, we report the association of the hydroxyl groups of diols via intra- or intermolecular H-bonds to enhance their reactivity as a base. Whereas the formation of an intermolecularly H-bonded dimer is requisite for diols of weak intramolecular H-bond to extract a proton from a model strong photoacid, a well-configured single diol molecule having an optimised intramolecular H-bond is revealed to serve as an effective Brønsted base with increased basicity...
September 18, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28922527/helical-threads-enantiomerically-pure-carbo-6-helicene-oligomers
#19
Cédric Schaack, Eric Sidler, Nils Trapp, François Diederich
We report the synthesis of enantiomerically pure carbo[6]helicene oligomers with buta-1,3-diyne-1,4-diyl bridges between the helicene nuclei. The synthesis of monomeric (±)-2,15-bis[(triisopropylsilyl)ethynyl]carbo[6]helicene was achieved in 25 % yield over six steps. Pure (+)-(P)- and (-)-(M)-enantiomers were obtained by HPLC on a chiral stationary phase. The dimeric (+)-(P)2 - and (-)-(M)2 -configured and the tetrameric (+)-(P)4 - and (-)-(M)4 -configured oligomers were obtained by sequential oxidative acetylenic coupling...
September 18, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28922509/molecular-switching-in-confined-spaces-effects-of-encapsulating-the-dha-vhf-photo-switch-in-cucurbiturils
#20
Michael Å Petersen, Brian Rasmussen, Nicolaj N Andersen, Stephan P A Sauer, Mogens Brøndsted Nielsen, Sophie R Beeren, Michael Pittelkow
Confinement of reactive chemical species uniquely affects chemical reactivity by restricting the physical space available and by restricting access to interactions with the solvent. In Nature, for example, confined protein binding pockets govern processes following photoisomerization reactions and the isomerizations themselves. Here we describe the first example of a dihydroazulene/vinylheptafulvene (DHA/VHF) photo-switch functioning in water, and we show how its switching behavior is strongly influenced by supramolecular interactions with a series of cucurbit[n]uril (CB) host molecules...
September 18, 2017: Chemistry: a European Journal
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