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Angewandte Chemie

Benoît Roubinet, Mariano L Bossi, Philipp Alt, Marcel Leutenegger, Heydar Shojaei, Sebastian Schnorrenberg, Shamil Nizamov, Masahiro Irie, Vladimir N Belov, Stefan W Hell
Reversibly photoswitchable 1,2-bis(2-ethyl-6-phenyl-1-benzothiophene-1,1-dioxide-3-yl)perfluorocyclopentenes (EBT) having fluorescent "closed" forms were decorated with four or eight carboxylic groups and attached to antibodies. Low aggregation, efficient photoswitching in aqueous buffers, specific staining of cellular structures, and good photophysical properties were demonstrated. Alternating light pulses of UV and blue light induce numerous reversible photochemical transformations between two stables states with distinct structures...
October 21, 2016: Angewandte Chemie
Agostino Biafora, Thilo Krause, Dagmar Hackenberger, Florian Belitz, Lukas J Gooßen
A system consisting of catalytic amounts of [(p-cym)RuCl2 ]2 /PEt3 ⋅HBF4 , K2 CO3 as the base, and NMP as the solvent efficiently mediates the ortho-C-H arylation of benzoic acids with aryl bromides at 100 °C. Replacing the phosphine ligand with the amino acid dl-pipecolinic acid enables the analogous transformation with aryl chlorides. The key advantage of this broadly applicable transformation is the use of an inexpensive ruthenium catalyst in combination with simple carboxylates as directing groups, which can either be tracelessly removed or used as anchor points for decarboxylative ipso substitutions...
October 21, 2016: Angewandte Chemie
Yingxia Zong, Yuanyuan Zhou, Minggang Ju, Hector F Garces, Amanda R Krause, Fuxiang Ji, Guanglei Cui, Xiao Cheng Zeng, Nitin P Padture, Shuping Pang
Methylamine-induced thin-film transformation at room-temperature is discovered, where a porous, rough, polycrystalline NH4 PbI3 non-perovskite thin film converts stepwise into a dense, ultrasmooth, textured CH3 NH3 PbI3 perovskite thin film. Owing to the beneficial phase/structural development of the thin film, its photovoltaic properties undergo dramatic enhancement during this NH4 PbI3 -to-CH3 NH3 PbI3 transformation process. The chemical origins of this transformation are studied at various length scales...
October 21, 2016: Angewandte Chemie
Liang Liu, Junnian Wei, Yue Chi, Wen-Xiong Zhang, Zhenfeng Xi
The chemistry of magnesium organocuprates, including their synthesis, structures, and reactions, remains underexplored. In this work, by taking advantage of the high reactivity and ready availability of magnesiacyclopentadienes, a series of magnesiacyclopentadiene-based organocuprates were synthesized and structurally characterized. A variety of CuX salts (X=Cl, Br, I, or alkynyl) were successfully applied to react with magnesiacyclopentadienes. Besides CuX salts, AgX salts (X=Cl, alkynyl) also undergwent the above reaction to afford the corresponding magnesium organoargentates...
October 21, 2016: Angewandte Chemie
John E Clements, Jason R Price, Suzanne M Neville, Cameron J Kepert
Materials that display multiple stepped spin crossover (SCO) transitions with accompanying hysteresis present the opportunity for ternary, quaternary, and quinary electronic switching and data storage but are rare in existence. Herein, we present the first report of a four-step hysteretic SCO framework. Single-crystal structure analysis of a porous 3D Hofmann-like material showed long-range ordering of spin states: HS, HS0.67 LS0.33 , HS0.5 LS0.5 , HS0.33 LS0.67 , and LS. These detailed structural studies provide insight into how multistep SCO materials can be rationally designed through control of host-host and host-guest interactions...
October 21, 2016: Angewandte Chemie
Benjamin S Gelfand, Racheal P S Huynh, Roger K Mah, George K H Shimizu
A crystalline and permanently porous copper phosphonate monoester framework has been synthesized from a tetraaryl trigonal phosphonate monoester linker. This material has a surface area over 1000 m(2)  g(-1) , as measured by N2 sorption, the highest reported for a phosphonate-based metal-organic framework (MOF). The monoesters result in hydrophobic pore surfaces that give a low heat of adsorption for CO2 and low calculated selectivity for CO2 over N2 and CH4 in binary mixtures. By careful manipulation of synthetic conditions, it is possible to selectively remove some of the monoesters lining the pore to form a hydrogen phosphonate while giving an isomorphous structure...
October 21, 2016: Angewandte Chemie
Chenting Yan, Zhifang Li, Xu-Qiong Xiao, Ningka Wei, Qiong Lu, Mitsuo Kira
A fluorostannylenoid (Cs(+) [R2 SnF](-) (9), R2 =(TMS)2 CCH2 CH2 C(TMS)2 ) was prepared by reacting a stable dialkylstannylene (R2 Sn (8), R2 =(TMS)2 CCH2 CH2 C(TMS)2 ) with cesium fluoride at room temperature in THF. While 9 is stable in THF and DME, removal of the solvent leads to the regeneration of stannylene 8. No reaction occurred when 8 was treated with CsF in a hydrocarbon solvent. Addition of dibenzo-21-crown-7 ether to the THF solution of stannylenoid 9 followed by usual workup affords the corresponding crystalline stannylenoid crown ether complex, the X-ray structural analysis of which revealed a fluorine-bridged contact ion-pair structure...
October 20, 2016: Angewandte Chemie
Curt Wentrup, Michèle J Regimbald-Krnel, Dennis Müller, Peter Comba
Variable-temperature NMR and ESR spectroscopic studies reveal that bis(dibenzo[a,i]fluorenylidene) 1 possesses a singlet ground state, 1(S0 ), while the 90° twisted triplet 1(T1 ) is populated to a small extent already at room temperature. Analysis of the increasing amount of paramagnetic 1(T1 ) at temperatures between 300 and 500 K yields the exchange interaction Jex /h c=3351 cm(-1) and a singlet-triplet energy splitting of 9.6 kcal mol(-1) , which is in excellent agreement with calculations (9...
October 20, 2016: Angewandte Chemie
Alina Tirla, Pablo Rivera-Fuentes
Photoactivatable phosphines that induce intracellular reductive stress are reported. The design of these probes takes advantage of the conjugate addition of trialkylphosphines to carbocyanine dyes, which can be reverted photochemically to produce the trialkylphosphine and a fluorescent reporter. The photochemical release depends on the efficiency of photoinduced electron transfer from the indolenine arm of the probe to the coumarin acceptor. These probes readily permeate the mammalian plasma membrane and can be photoactivated in live cells...
October 20, 2016: Angewandte Chemie
David Gau, Raphael Nougué, Nathalie Saffon-Merceron, Antoine Baceiredo, Abel De Cózar, Fernando P Cossío, Daisuke Hashizume, Tsuyoshi Kato
A donor-stabilized 1,3-disila-2,4-diazacyclobutadiene presents an exceptionally short nonbonded Si⋅⋅⋅Si distance (2.23 Å), which is as short as that of Si=Si bonds (2.15-2.23 Å). Theoretical investigations indicate that there is no bond between the two silicon atoms, and that the unusual geometry can be related to a significant coulomb repulsion between the two ring nitrogen atoms. This chemical pressure phenomenon could provide an alternative and superior way of squeezing out van der Waals space in highly strained structures, as compared to the classical physical methods...
October 20, 2016: Angewandte Chemie
Zhuolei Zhang, Shenqiang Ren
Luminescent network: Colloidal excimer superstructures with unique optical and electronic properties have recently been described. Ground-state gold cluster cores were held together by the hydrogen-bonding network formed by their capping ligands, which enabled excimer formation.
October 20, 2016: Angewandte Chemie
David A Leigh
In the beginning…: The Nobel Prize in Chemistry 2016 goes to three of the pioneers of the field of synthetic molecular machines, Jean-Pierre Sauvage, Sir J. Fraser Stoddart, and Ben L. Feringa. Their work has led from the reliable synthesis of rotaxanes and catenanes to molecular rotary motors, shuttles, muscles, and other devices.
October 20, 2016: Angewandte Chemie
Bruno L Oliveira, Zijian Guo, Omar Boutureira, Ana Guerreiro, Gonzalo Jiménez-Osés, Gonçalo J L Bernardes
The unstrained S-allyl cysteine amino acid was site-specifically installed on apoptosis protein biomarkers and was further used as a chemical handle and ligation partner for 1,2,4,5-tetrazines by means of an inverse-electron-demand Diels-Alder reaction. We demonstrate the utility of this minimal handle for the efficient labeling of apoptotic cells using a fluorogenic tetrazine dye in a pre-targeting approach. The small size, easy chemical installation, and selective reactivity of the S-allyl handle towards tetrazines should be readily extendable to other proteins and biomolecules, which could facilitate their labeling within live cells...
October 20, 2016: Angewandte Chemie
Franziska Fischer, Sebastian Greiser, Dietmar Pfeifer, Christian Jäger, Klaus Rademann, Franziska Emmerling
Benzamide has been known for its polymorphism for almost 200 years. Three polymorphic forms are described. To date, it was only possible to crystallize a metastable form in a mixture together with the thermodynamically most stable form I. A complete transformation of form I into the metastable form III by mechanochemical treatment has been achieved. Catalytic amounts of nicotinamide seeds were used to activate the conversion by mechanochemical seeding. NMR experiments indicated that the nicotinamide molecules were incorporated statistically in the crystal lattice of benzamide form III during the conversion...
October 20, 2016: Angewandte Chemie
Deliang Yi, Qian Zhang, Yinghua Liu, Jiaying Song, Yi Tang, Frank Caruso, Yajun Wang
We report the synthesis of chemically asymmetric silica nanobottles (NBs) with a hydrophobic exterior surface (capped with 3-chloropropyl groups) and a hydrophilic interior surface for spatially selective cargo loading, and for application as nanoreactors and nanomotors. The silica NBs, which have a "flask bottle" shape with an average diameter of 350 nm and an opening of ca. 100 nm, are prepared by anisotropic sol-gel growth in a water/n-pentanol emulsion. Due to their chemically asymmetric properties, nanoparticles (NPs) with hydrophilic or hydrophobic surface properties can be selectively loaded inside the NBs or on the outside of the NBs, respectively...
October 20, 2016: Angewandte Chemie
Christoph Göbl, Moritz Resch, Madeleine Strickland, Christoph Hartlmüller, Martin Viertler, Nico Tjandra, Tobias Madl
The study of intrinsically disordered proteins (IDPs) by NMR often suffers from highly overlapped resonances that prevent unambiguous chemical-shift assignments, and data analysis that relies on well-separated resonances. We present a covalent paramagnetic lanthanide-binding tag (LBT) for increasing the chemical-shift dispersion and facilitating the chemical-shift assignment of challenging, repeat-containing IDPs. Linkage of the DOTA-based LBT to a cysteine residue induces pseudo-contact shifts (PCS) for resonances more than 20 residues from the spin-labeling site...
October 20, 2016: Angewandte Chemie
Gonzalo Abellán, Vicent Lloret, Udo Mundloch, Mario Marcia, Christian Neiss, Andreas Görling, Maria Varela, Frank Hauke, Andreas Hirsch
Black phosphorus (BP) was functionalized with organic moieties on the basis of liquid exfoliation. The treatment of BP with electron-withdrawing 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) led to electron transfer from BP to the organic dopant. On the other hand, the noncovalent interaction of BP with a perylene diimide was mainly due to van der Waals interactions but also led to considerable stabilization of the BP flakes against oxygen degradation.
October 20, 2016: Angewandte Chemie
Michael H Wang, Karl A Scheidt
N-Heterocyclic carbene (NHC) catalysis has emerged as a powerful stratagem in organic synthesis to construct complex molecules primarily by polarity reversal (umpolung) approaches. These unique Lewis bases have been used to generate acyl anions, enolates, and homoenolates in catalytic fashion. Recently, a new strategy has emerged that dramatically expands the synthetic utility of carbene catalysis by leveraging additional activation modes: cooperative catalysis. The careful selection and balance of cocatalysts have led to enhanced reactivity, increased yields, and improved stereoselectivity...
October 20, 2016: Angewandte Chemie
Benjamin J Frogley, L James Wright
Metalla-analogues of archetypal aromatic molecules are attracting ever increasing interest. Although metallabenzenes (which fall within this class) have been well studied, fused-ring metallabenzenes are rare and of the linear polycyclic metallaaromatic hydrocarbons, only metallanaphthalene is known. Herein we report the first metallaanthracene, [Ir(C13 H8 {CH2 CO2 Me-5})Cl(PPh3 )2 ]O3 SCF3 (5), which represents the next member of this series of polycyclic compounds. Structurally, 5 has a number of features in common with anthracene including fused-ring planarity and bond-length alternation...
October 20, 2016: Angewandte Chemie
Yumiko Mizukoshi, Koh Takeuchi, Misa Arutaki, Yuji Tokunaga, Takeshi Takizawa, Hiroyuki Hanzawa, Ichio Shimada
The thermodynamic properties of a ligand in the bound state affect its binding specificity. Strict binding specificity can be achieved by introducing multiple spatially defined interactions, such as hydrogen bonds and van der Waals interactions, into the ligand-receptor interface. These introduced interactions are characterized by restricted local dynamics and improved surface complementarity in the bound state. In this study, we experimentally evaluated the local dynamics and the surface complementarity of weak-affinity ligands in the receptor-bound state by forbidden coherence transfer analysis in free-bound exchange systems (Ex-FCT), using the interaction between a ligand, a myocyte-enhancer factor 2A (MEF2A) docking peptide, and a receptor, p38α, as a model system...
October 20, 2016: Angewandte Chemie
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