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Chemistry: a European Journal

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https://www.readbyqxmd.com/read/28817213/bismuthanes-as-hemilabile-donors-in-an-o2-activating-palladium-0-complex
#1
Karolin Materne, Beatrice Braun-Cula, Christian Herwig, Nicolas Frank, Christian Limberg
A xanthene-based bismuthane/phosphane chelating ligand has been accessed that has enabled the synthesis of a palladium(0) bismuthane complex. The bismuthane donor proved to be hemilabile as it switched to a dangling position upon addition of O2 that gave a palladium(II) peroxide complex. Unlike the corresponding 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) palladium peroxide, the bismuth analogue could be employed for catalytic phosphane oxidation and oxidative phenol coupling.
August 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28816406/phosphinous-acid-assisted-hydration-of-nitriles-understanding-the-controversial-reactivity-of-osmium-and-ruthenium-catalysts
#2
Rebeca González-Fernández, Pascale Crochet, Victorio Cadierno, M Isabel Menéndez, Ramón López
The synthesis and catalytic behaviour of the osmium(II) complexes [OsCl2(6-p-cymene)(PR2OH)] [R = Me (2a), Ph (2b), OMe (2c), OPh (2d)] in nitrile hydration reactions is presented. Among them, the best catalytic results were obtained with the phosphinous acid derivative [OsCl2(6-p-cymene)(PMe2OH)] (2a), which selectively provided the desired primary amides in excellent yields and short times at 80 ºC, employing directly water as solvent, and without the assistance of any basic additive (TOF values up to 200 h-1)...
August 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28816404/multivalency-increases-the-binding-strength-of-rgd-peptidomimetic-paclitaxel-conjugates-to-integrin-%C3%AE-v%C3%AE-3
#3
Cesare Gennari, André Raposo Moreira Dias, Arianna Pina, Alberto Dal Corso, Daniela Arosio, Laura Belvisi, Luca Pignataro, Michele Caruso
Herein we report the synthesis of three multimeric RGD peptidomimetic-paclitaxel conjugates featuring a number of αVβ3 integrin ligands ranging from 2 to 4 (compounds 7-9). These constructs were assembled by conjugation of the integrin αVβ3 ligand cyclo[DKP-RGD]-CH2NH2 (2) with paclitaxel (3) via a 2'-carbamate with a self-immolative spacer, the lysosomally cleavable Val-Ala dipeptide linker, a multimeric scaffold, a triazole linkage, and finally a PEG spacer. Two monomeric conjugates (compounds 5-6) were also synthesized as reference compounds...
August 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28816379/from-enzymes-to-functional-materials-towards-activation-of-small-molecules
#4
Frauke Möller, Stefan Piontek, Reece G Miller, Ulf-Peter Apfel
The design of non-noble metal containing heterogenous catalysts for the activation of small molecules is of utmost importance for our society. While nature possesses very sophisticated machineries to perform such conversions, rationally designed catalytic materials are rare. Herein, we aim to raise the awareness of the overall common design and working principles of catalysts and "break down the boundaries" between biology, chemistry and material sciences.
August 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28816377/controlled-growth-of-metal-organic-frameworks-on-polymer-brushes
#5
Liman Hou, Mingdong Zhou, Xiaozhe Dong, Lei Wang, Zhigang Xie, Dewen Dong, Ning Zhang
Polymer brushes are for the first time used to induce the synthesis of metal-organic frameworks (MOFs). The semi-fixed polymer chains provide a confined environment, which allows a mild growth of MOFs in-between polymer chains to give surface-attached spherical MOF nanoparticles, in contrast to the larger MOF cubics/plates formed simultaneously in solution. Polymer brushes bearing carboxylate acid functionalities are indispensible for the formation of surface bound MOFs, while no MOF nanoparticles are observed on neutral polymer brushes...
August 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28816371/transition-metal-free-cleavage-of-co
#6
Marc Devillard, Bas de Bruin, Maxime Siegler, Jarl Ivar van der Vlugt
Tertiary silane 1H, 2-((diphenylsilyl)methyl)-6-methylpyridine, reacts with tris(pentafluorophenyl)borane (BCF) to form the intramolecular pyridine-stabilized silylium 1+-HBCF. The corresponding 2-((diphenylsilyl)methyl)-pyridine, lacking the methyl-group on the pyridine ring, forms classic N(py)→B adduct 2H-BCF featuring an intact silane Si-H fragment. Complex 1+-HBCF promotes cleavage of the C≡O triple bond in carbon monoxide with double C-Csp2 bond formation, leading to complex 3 featuring a B-(diarylmethyl)-B-aryl-boryloxysilane fragment...
August 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28816368/one-pot-self-assembly-of-peptide-based-cage-type-nanostructures-using-orthogonal-ligations
#7
Eline Bartolami, Jérémie Knoops, Yannick Bessin, Mathieu Fossépré, Joseph Chamieh, Pascal Dumy, Mathieu Surin, Sebastien Ulrich
The designed arrangement of biomolecular entities within monodisperse nanostructures is an important challenge toward functional biomaterials. We report herein a method for the formation of water-soluble peptide-based cages using orthogonal ligation reactions - acylhydrazone condensation and thiol-maleimide addition. The results show that using pre-organized cyclic peptides and heterobifunctional spacers as building blocks and a set of orthogonal and chemoselective ligation reactions enable cage formation in one-pot from six components and through eight reactions...
August 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815866/catalytic-intramolecular-cycloaddition-reactions-using-a-discrete-molecular-architecture
#8
Partha Sarathi Mukherjee, Bijan Roy, Anthonisamy Devaraj, Rupak Saha, Suprita Jharimune, Ki-Whan Chi
A discrete tetragonal tube-shaped complex (MT-1) has been synthesized by coordination-driven self-assembly of a carbazole-based tetraimidazole donor L and a Pd(II) 90° acceptor, viz. [cis-(dppf)Pd(OTf)2] (dppf = diphenylphosphino ferrocene, OTf = CF3SO3-). Complex MT-1 was characterized by multinuclear NMR, ESI-MS and single crystal X-ray diffraction analysis (SCXRD), which showed its symmetrical tetrafacial tube-shaped architecture possessing a large cavity described by four aromatic walls. This coordination cage was successfully utilized as a molecular vessel to perform intramolecular cycloaddition reactions of O-allylated benzylidinebarbituric acid derivatives inside its confined nanospace...
August 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815776/a-photochemical-and-electrochemical-triggered-bis-hydrazone-switch
#9
Mónica A Gordillo, Mónica Soto-Monsalve, Christian C Carmona-Vargas, Gustavo Gutierrez, Richard F D'vries, Jean-Marie Lehn, Manuel N Chaur
Herein, we report the synthesis of a double hydrazone capable of undergoing photochemical E/Z isomerization through the imine double bonds. The bis(hydrazone) 1-E,E can be considered as a "two-arm" system in which the controlled movement of each arm is obtained by photo-modulation, making possible the appearance of two isolable metastable isomeric states 1-E,Z and 1-Z,Z. Such states are characterized by very specific structural, optical and electrochemical properties. The latter, allows the reversible return from either 1-E,Z or 1-Z,Z to the 1-E,E state...
August 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815775/pet-switching-mechanism-of-a-napthalimide-derivative-with-its-solvatochromic-behaviour-an-experimental-and-theoretical-study-with-in-cell-investigations
#10
Dipti Singharoy, Sourav Chowdhury, Soumya Sundar Mati, Swadesh Ghosh, Krishnananda Chattopadhyay, Subhash Chandra Bhattacharya
The sole existence of t-bone shape napthalimide derivative [2-(2-aminoethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione] (NAP) which in turn gives rise to a PET mechanism, has been established using a combination of experimental and theoretical studies. In parallel an in vitro-in cell PET mechanism has also been shown. To understand the photo physics of NAP, solvent studies have been carried out in different solvents. In addition, theoretical calculations have been resorted to explain the spectroscopic properties through optimized structures...
August 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815774/excitonically-coupled-states-in-crystalline-coordination-networks
#11
Ritesh Haldar, Antoine Mazel, Reetu Joseph, Michael Adams, Ian Howard, Bryce Richards, Manuel Tsotsalas, Engelbert Redel, Stephane Diring, Fabrice Odobel, Christof Wöll
When chromophores are brought into close proximity, noncovalent interactions (π-π/CH-π) can lead to the formation of excitonically coupled states, which bestow new photophysical properties upon the aggregates. Since the properties of the new states not only depend on the strength of intermolecular interactions, but also on the relative orientation, supramolecular assemblies, where these parameters can be varied in a deliberate fashion, provide novel possibilities for the control of photophysical properties...
August 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815946/model-catalytic-studies-of-novel-liquid-organic-hydrogen-carriers-indole-indoline-and-octahydroindole-on-pt-111
#12
Matthias Schwarz, Philipp Bachmann, Thais Nascimento Silva, Susanne Mohr, Marlene Scheuermeyer, Florian Späth, Udo Bauer, Fabian Düll, Johann Steinhauer, Chantal Hohner, Tibor Döpper, Heshmat Noei, Andreas Stierle, Christian Papp, Hans-Peter Steinrück, Peter Wasserscheid, Andreas Görling, Jörg Libuda
Indole derivatives were recently proposed as potential Liquid Organic Hydrogen Carriers (LOHC) for storage of renewable energies. In this work, we have investigated the adsorption, dehydrogenation and degradation mechanisms in the indole/indoline/octahydroindole system on Pt(111). We have combined infrared reflection absorption spectroscopy (IRAS), X-ray photoelectron spectroscopy (XPS) and density functional (DF) calculations. Indole multilayers show a crystallization transition at 200 K, in which the molecules adopt a strongly tilted orientation, before the multilayer desorbs at 220 K...
August 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815903/rhenium-loaded-tio2-a-highly-versatile-and-chemoselective-catalyst-for-the-hydrogenation-of-carboxylic-acid-derivatives-and-the-n-methylation-of-amines-using-h2-and-co2
#13
Takashi Toyao, Hakim S M A Siddiki, Yoshitsugu Morita, Takashi Kamachi, Abeda S Touchy, Wataru Onodera, Kenichi Kon, Shinya Furukawa, Hiroko Ariga, Kiyotaka Asakura, Kazunari Yoshizawa, Ken-Ichi Shimizu
Herein, we report a heterogeneous TiO2-supported Re catalyst (Re/TiO2) that promotes various selective hydrogenation reactions, e.g. hydrogenation of esters to alcohols, hydrogenation of amides to amines, and N-methylation of amines using H2 and CO2. Initially, Re/TiO2 was evaluated in the context of the selective hydrogenation of 3-phenylpropionic acid methyl ester to afford 3-phenylpropanol (pH2 = 5 MPa, T = 180 ºC), where revealed a superior performance relative to other catalysts explored in this study...
August 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815887/viologens-and-their-application-as-functional-materials
#14
Laura Striepe, Thomas Baumgartner
Organic materials have recently gained considerable attention for electronic applications, improving performance and sustainability to current technologies. Commercialized metal-based systems are generally expensive, toxic and difficult to recycle, however organic materials offer promising solutions. Viologens, N,N' di-quaternized bipyridyl salts, are a well-studied species exhibiting three reversible redox states, possessing valuable electrochromic and electron-accepting properties. These properties can be fine-tuned through synthesis by altering the nitrogen substituents and various counteranions...
August 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815875/the-pathogenic-a2v-mutant-exhibits-distinct-aggregation-kinetics-metal-site-structure-and-metal-exchange-of-the-cu2-a%C3%AE-complex
#15
Lars Hemmingsen, Arun K Somavarapu, Fei Shen, Kaare Teillum, Jingdong Zhang, Susanne Mossin, Peter W Thulstrup, Morten J Bjerrum, Manish K Tiwari, Daniel Szunyogh, Peter M Søfotfe, Kasper K Kepp
A prominent current hypothesis is that impaired metal ion homeostasis may contribute to Alzheimer's Disease (AD). We elucidate the interaction of Cu2+ with wild-type (WT) Aβ1-40 and the genetic variants A2T and A2V which display increasing pathogenicity as A2T<WT<A2V. Cu2+ significantly extends the lag phase in aggregation kinetics, in particular for the pathogenic A2V variant. Additionally, a rapid, initial, low intensity ThT response is observed, possibly reflecting formation of Cu2+ induced amorphous aggregates, as supported by AFM and CD spectroscopy, again most notably for the A2V variant...
August 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815856/molecular-dynamics-insights-into-polyamine-dna-binding-modes-implications-for-cross-link-selectivity
#16
Emmanuelle Bignon, Chen-Hui Chan, Christophe Morell, Antonio Monari, Jean-Luc Ravanat, Elise Dumont
Biogenic polyamines, which play a role in DNA condensation and stabilization, are ubiquitous and are found at millimolar concentration in the nucleus of eukaryotic cells. The interaction modes of three polyamines-putrescine (Put), spermine (Spm), and spermidine (Spd)-with a self-complementary 16 base pair (bp) duplex, are investigated by all-atom explicit-solvent molecular dynamics. The length of the amine aliphatic chain leads to a change of the interaction mode from minor groove binding to major groove binding...
August 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815836/-2-2-paracyclophanes-with-n-heterocycles-as-ligands-for-mono-and-dinuclear-ruthenium-ii-complexes
#17
Carolin Braun, Martin Nieger, Werner R Thiel, Stefan Bräse
The [2.2]paracyclophane with its unique structure allows the design of unusual 3D structures by functionalization of this rigid and stable hydrocarbon scaffold. Therefore different mono- and homodisubstituted [2.2]paracyclophanes with pyridyl, pyrimidyl and oxazolinyl substituents were developed in order to evaluate their ability as bridging ligands for two ruthenium centres. With the successfully synthesized [2.2]paracyclophane-based N-donor functions, the cycloruthenation reaction using [RuCl2(p-cymene)]2 as precursor was explored...
August 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815818/an-unprecedented-blue-chromophore-found-in-nature-by-a-chemistry-first-and-molecular-networking-approach-discovery-of-dactylocyanines-a-h
#18
Natacha Bonneau, Guanming Chen, David Lachkar, Asmaa Boufridi, Jean-François Gallard, Pascal Retailleau, Sylvain Petek, Cécile Debitus, Laurent Evanno, Mehdi Beniddir, Erwan Poupon
Guided by a "Chemistry First" approach using molecular networking, eight new bright-blue colored natural compounds, namely dactylocyanines A-H (3-10), were isolated from the Polynesian marine sponge Dactylospongia metachromia. Starting from ilimaquinone (1), an hemisynthetic phishing probe (2) was prepared for annotating and matching structurally related natural substances in D. metachromia crude extract network. This strategy allowed characterizing for the first time in Nature the blue zwitterionic quinonoid chromophore...
August 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815816/coordination-behavior-of-planar-chiral-cyclic-amino-ferrocenyl-carbene-in-iridium-complexes
#19
Yuta Shikata, Risa Yasue, Kazuhiro Yoshida
Iridium complexes bearing a new type of chiral carbene ligand, cyclic (amino)(ferrocenyl)carbene (CAFeC), were prepared. The complexes, which are quite stable in air and moisture, were fully characterized by NMR spectroscopy and X-ray diffraction analysis. The NMR spectra of the dicarbonyl complex [IrCl(CO)2(CAFeC)] showed signals for two isomers in solution, which were assigned to diastereomeric rotamers arising from the rotation of the chiral CAFeC ligand around the axes of the Ir-Ccarbene bond. IR spectroscopy of the dicarbonyl complex revealed that the donor strength of CAFeC is much higher than those of classic N-heterocyclic carbenes (NHCs) and comparable to those of cyclic amino alkyl carbenes (CAACs)...
August 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815815/synthesis-optical-properties-and-dna-interaction-of-new-diquats-based-on-triazolopyridines-and-triazoloquinolines
#20
Pedro J Llabres-Campaner, Lluís Guijarro, Claudia Giarratano, Rafael Ballesteros-Garrido, Ramón J Zaragozá, M José Aurell, Enrique García-España, Rafael Ballesteros, Belén Abarca
New diquat derivatives based on [1,2,3]triazolo[1,5-a]pyridine and [1,2,3]triazolo[1,5-a]quinoline have been synthesized in excellent yields. To evaluate the effect of the alkyl bridge length, ethane and propane dibromo alkane substrates were used for their synthesis. Theoretical calculations predicted a very small energetic barrier between the two possible enantiomers P (Ra ) and M (Sa ), which makes them very difficult to resolve. Thermal denaturation studies, UV/Visible spectroscopy, and fluorescence titrations with ct-DNA evidenced the intercalation of the quinoline derivatives in DNA...
August 16, 2017: Chemistry: a European Journal
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