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PubMed Journal Database | Chemistry (Weinheim an der Bergstrasse, Germany) RSS

09:05 EDT 27th May 2019 | BioPortfolio

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Showing PubMed Articles 1–25 of 2,500+ from Chemistry (Weinheim an der Bergstrasse, Germany)

Crystal structures of DOTMA chelates from Ce3+ to Yb3+: evidence for a continuum of metal ion hydration states.

The crystal structures of chelates formed between each stable paramagnetic lanthanide ion and DOTMA are described. A total of 23 individual chelates structures were obtained, in each chelate the coordiantion geometry around the metal ion is best described as a twisted square antiprism (torsion angle -25.0° - -31.4°). Despite the uniformity of the general coordination geometry provided by the DOTMA ligand, there is a considerable variation in the hydration state of each chelate. The early Ln3+ chelates are...

Reaching Green: Heterocycle Synthesis by Transition Metal-Catalyzed C-H Functionalization in Sustainable Medium.

Catalytic C-H functionalization has emerged as an efficient alternative to traditional coupling reactions. However, some of these reactions depend on the environmentally harmful solvents, weakening the overall green nature of these methods. As organic processes consume a large amount of solvents, the use of less harmful solvents enhance the sustainability of these reactions. Herein, we present an overview of transition metal-catalyzed C-H functionalization reactions for the synthesis of heterocycles in sust...

Dismutation of Titanium Sub-oxide into TiO and TiO2 with Structural Hierarchy Assisted by Ammonia Halides.

Black TiO2-x attracts enormous attention due to its large solar adsorption and improved conductivity. In this work, a novel structure of TiO2-x with conductive TiO layer, performing full-spectrum absorption, was one-step synthesized by the unforeseen dismutation reaction of Titanium sub-oxides (TinO2n-1) in ammonium halide atmosphere. For this new reaction, a possible mechanism of decomposition - etching - disproportionation - rehydrolysis process was proposed. The vital intermediate reactant TiCl4 verifyin...

Zinc Tetracyanoplatinate: A Reversible Luminescence-Based Ammonia Sensor.

ZnPt(CN) was shown to be an effective material for ammonia sensing, and can be synthesized using either solution or mechanochemical methods. A combination of luminescence and Raman spectroscopy revealed that multiple species are involved in the reaction between ammonia and ZnPt(CN) . The crystal structure of one of these species, Zn(NH ) Zn(NH ) (Pt(CN) ) , was elucidated. Detection of ammonia vapor down to 50 ppm in air was accomplished by monitoring the luminescence spectrum. The reaction between ZnPt(C...

Metastable 9-fluorenone: Blue-shifted fluorescence, single-crystal-to-single-crystal reactivity, and evaluation as a multi-modal fingermark visualization treatment.

A metastable form of 9-fluorenone (MS9F) has been characterized using Raman spectroscopy, fluorimetry, and X-ray diffraction techniques. MS9F emits blue fluorescence (λmax = 495 nm) upon 365 nm irradiation and undergoes a single-crystal-to-single-crystal (SCSC) transformation to reach the ground state form (GS9F) over ca 30 minutes, whereupon it emits the expected green fluorescence. A structure-property relationship for this fluorescent behavior has been posited. MS9F and GS9F were applied as a means of v...

Red-shifted substrates for FAST fluorogen-activating protein based on the GFP-like chromophores.

In this paper, we present a novel genetically encoded fluorescent tag for live cell microscopy. This tag is composed of previously published fluorogen-activating protein FAST and a novel fluorogenic derivative of GFP-like chromophore with red fluorescence. The reversible binding of the novel fluorogen and FAST is accompanied by three orders of magnitude increase in red fluorescence (580-650 nm). The proposed dye instantly stains target cellular proteins fused with FAST, washes out in a minute timescale, and...

Dual Activation of Aromatic Diels-Alder Reactions.

We have analyzed the unusually fast Diels-Alder reactivity of [5]cyclophanes using density functional theory at the BLYP-D3(BJ)/TZ2P level. The computations were guided by an integrated activation strain and Kohn-Sham molecular orbital analysis. It is revealed why both [5]metacyclophane and [5]paracyclophane exhibit a significant rate enhancement compared to their planar benzene analog. The activation strain analyses reveal the enhanced reactivity to originate from (i) pre-distortion of the aromatic core re...

A histidine residue and a tetranuclear cuprous-thiolate cluster dominate the copper loading landscape of a copper storage protein from Streptomyces lividans.

The chemical basis for protecting organisms against the toxic effect imposed by excess cuprous ions is to constrain this through high-affinity binding sites that employ cuprous-thiolate coordination chemistries. In bacteria, a family of cysteine rich four helix-bundle proteins utilise thiolate chemistry to bind up to 80 cuprous ions. These proteins have been termed copper storage proteins (Csp). The present study investigates cuprous ion loading to the Csp from Streptomyces lividans (SlCsp) using a combinat...

Investigating electronic communications in meso-meso ethene-bridged unsymmetrical diporphyrins.

At the focal point of this work is the photophysical characterization of three meso-meso ethene-bridged diporphyrins featuring diverse metallation pattern. Detailed investigations by means of cyclic voltammetry, absorption, fluorescence, and femto-/nanosecond transient absorption spectroscopy revealed the impact of open-shell nickel (II) on the electronic communication in ethene-bridged heterobimetallic diporphyrins.

Delineation of the Critical Parameters of Salt Catalysts in the N-Formylation of Amines with CO2.

N-formylation of amines combining CO2 as a C1 source with a hydrosilane reducing agent is a convenient route for the synthesis of N-formylated compounds. A large number of salts including ionic liquids (ILs) have been shown to efficiently catalyze the reaction and, yet, the key features of the catalyst remain unclear and the best salt catalysts for the reaction remain unknown. Here we demonstrate the detrimental effect of ion pairing on the catalytic activity and illustrate ways in which the strength of the...

Synthesis and Evaluation of Azolium-Based Halogen Bond Donors.

A method for the synthesis of iodinated imidazolium and triazolium N-heterocyclic halogen bond donor catalysts has been developed. This approach was applied to the synthesis of a variety of 1,2,4-triazolium salts to prepare a series of novel chiral halogen bond donor catalysts. The counterions of the iodinated triazoliums can be readily exchanged with chiral and achiral non-coordinating counterions to produce unique scaffolds. Their ability to promote/catalyse a conjugate addition reaction with indole was i...

Structure Pattern Based Total Synthesis.

In this article we summarize the concept of structure pattern recognition and its application to total synthesis. We show that this strategic concept can lead to a drastic increase of synthetic efficiency, by applying it to the two biogenetically unrelated natural product families sarpagine and stemona alkaloids. To showcase its potential, it is compared with some elegant target oriented syntheses. We wish to advert the reader to the importance of strategic planning and synthesis design.

Through Space Spin Coupling in a Silver(II) Porphyrin Dimer upon Stepwise Oxidations: AgII/AgII, AgII/AgIII and AgIII/AgIII Metallophilic Interactions.

Metallophilic interactions between closed shell metal ions are becoming extremely popular tool for a variety of high-end materials related applications. There is no systematic investigation so far to estimate the structure and energy characteristics for metallophilic interactions between AgII/AgII (d9/d9), AgIII/AgIII (d8/d8) and also mixed-valent AgII/AgIII (d9/d8) complexes which has been demonstrated in the present study. Both interporphyrinic and inter-metallic interactions have been investigated upon s...

Fluorine-Containing Drugs Approved by the FDA in 2018.

Over the last two decades, fluorine substitution has become one of the essential structural traits in modern pharmaceuticals. Thus, about half of the most successful drugs (blockbuster drugs) contain fluorine atom. In this review, we profile 17 fluorine-containing drugs approved by the FDA in 2018. The newly approved pharmaceuticals feature several types of aromatic F- and CF3-, aliphatic (CF2) substitution, offering advances in treatment of various diseases, including cancer, HIV, malarial and smallpox inf...

Exploring the chemistry of non-sticky sugars: Synthesis of polyfluorinated carbohydrate analogs of D-allopyranose.

There is a growing interest in the preparation of polyfluorinated carbohydrates. A limited number of fluorohexopyranosides have been used in biological investigations because of the synthetic challenge they present. Hence, we report the synthesis of fluorinated homodimer, fluorodisaccharides, C-terminal fluoroglycopeptides, lipoic acid fluoroglycoconjugate and trifluoroallopyranoside derivatives functionalized at C-6. Our strategy uses levoglucosan as inexpensive starting material and unveil an approach to ...

Organic-Inorganic Hybrid Gold Halide Perovskites: Structural Diversity via Cation Size.

Crystal structures of a series of organic-inorganic hybrid gold iodide perovskites, formulated as A2[AuII2][AuIIII4](A = methylammonium (MA) (1) and formamidinium (FA) (2)), A'2[I3]1-x[AuII2]x[AuIIII4](A' = imidazolium (IMD) (3), guanidinium (GUA) (4), dimethylammonium (DMA) (5), pyridinium (PY) (6), and piperizinium (PIP) (7)), systematically changed depending on the cation size. In addition, triiodide (I3-) ions were partly incorporated into the AuI2- sites of 3-7, whereas they were not incorporated into ...

Emission color control in polymer film by memorized fluorescence solvatochromism due to a new class of totally-organic fluorescent nanogel particles.

This paper introduces a new class of totally-organic fluorescent nanogel particles and their exceptionally specific behaviors based on their unique structures, which draws a sharp line from conventional fluorophore-doped and fluorophore-branched type particles. The nanogel particles whose diameters could be controlled by adjusting reaction conditions such as the solvent system, were spontaneously fabricated with a spherical shape by the direct polymerization of non-heterocyclic aromatic compounds such as 2,...

Chirality Controlled Self-Assembly of Amphiphilic Dibenzo6helicenes into Langmuir-Blodgett Thin Films.

Racemic and highly enantioenriched 3-methoxycarbonyl, 3-carboxy and 3-hydroxymethyl derivatives of dibenzo[6]helicene were prepared. The Langmuir layers of these helicenes were formed at the air-water interface and transferred onto solid substrates to afford Langmuir-Blodgett films, which were then studied by ambient atomic force microscopy and (chir)optical spectroscopy. Significant differences were found in the behaviour of the Langmuir layers as well as in the morphology, UV-Vis, ECD and fluorescence spe...

Intrinsic Photophysics of Light-harvesting Charge-tagged Chlorophyll a and b Pigments.

Chlorophylls a and b (Chla/b) are responsible for light-harvesting by photosynthetic proteins in plants. They display broad absorption in the visible region with multiple bands, due to the asymmetry of the macrocycle and strong vibronic coupling. Their photophysics relies on the microenvironment, with regard to transition energies as well as quenching of triplet states. Here we firmly establish the splitting of the Q and Soret bands into x and y polarized bands for the isolated molecules in vacuo, and resol...

Highly proton-conductive zinc metal-organic framework based on nickel(II) porphyrinylphosphonate.

The design of new solid-state proton-conducting materials, is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF (IPCE-1Ni), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55 × 10-3 S cm-1 at 75 °C and 80% relative humidity).

Asymmetric Catalysis in Liquid Confinement: Probing the Performance of Novel Chiral Rhodium Diene Complexes in Microemulsions and Conventional Solvents.

The role of liquid confinement on the asymmetric Rh catalysis was studied using the 1,2-addition of phenylboroxine 2 to N-tosylimine 1 in the presence of [RhCl(C2H4)2]2 and chiral diene ligands as benchmark reaction. To get access to Rh complexes of different polarity, enantiomerically pure C2-symmetric p-substituted 3,6-diphenylbicyclo[3.3.0]octadienes 4 and diastereomerically enriched unsymmetric norbornadienes 5 and 6 carrying either the Evans or the SuperQuat auxiliary were synthesized. A microemulsion ...

Functionalized Fluorophosphonium Ions.

Efforts to prepare an elusive donor-free phosphenium ion, [R2P]+, led us to synthesize functionalized fluorophosphonium cations of the type [R2P(F)X]+ (X = SiEt3, H, F), which were obtained from the related neutral fluorophosphines R2PF and R2PF3 upon protonation and reaction with solvated [Et3Si]+ ions (R = 2,6-Mes2C6H3). The hypothetical reductive elimination of [R2P(F)SiEt3]+ and [R2P(F)H]+ affording [R2P]+, Et3SiF and HF, respectively, was calculated to be endothermic by 40.1 and 190.6 kJ mol-1.

Cascade amplified time-resolved fluorescent assay driven by enzyme-integrated catalytic compartment as an artificial multi-enzyme complex.

We here report a simple and efficient strategy of fabricating artificial multi-enzyme complex (MEC) based on the integration of natural enzyme with catalytic compartment. As a proof of concept, this strategy was demonstrated by selecting cholesterol oxidase (ChOx) and Ce(III)-based nanoscale coordination polymer (Ce-NCP) with peroxidase-like activity as the models, which forms ChOx@Ce-NCP. Benefiting from the confinement and sheltering effects of Ce-NCP, superior cascade activity and stability in harsh envi...

A Rhenium Isonitrile Complex Induces Unfolded Protein Response-Mediated Apoptosis in Cancer Cells.

Complexes of the element Re have recently been shown to possess promising anticancer activity via mechanisms of action that are distinct from the conventional metal-based drug cisplatin. In this study, we report our investigations on the anticancer activity of the complex [Re(CO)3(dmphen)(p-tol-ICN)]+ (TRIP) where dmphen = 2,9-dimethyl-1,10-phenanthroline and p-tol-ICN = 4-methylphenyl isonitrile. TRIP was synthesized via literature methods and exhaustively characterized. This compound exhibits potent in vi...

Oxygen-Bridged Ga2(Et)3(OTeF5)3 and the Weakly Coordinating Anions Ga(Et)(OTeF5)3- and Ga(OTeF5)4.

Salts of the weakly coordinating anions [Ga(OTeF5)4]- as well as [Ga(Et)(OTeF5)3]- and the neutral Ga2(Et)3(OTeF5)3 are synthesized and characterized by spectroscopic methods and single crystal x-ray diffraction. Ga2(Et)3(OTeF5)3 is formed by treating GaEt3 with pentafluoroorthotelluric acid (HOTeF5) and reacts with PPh4Cl and CPh3Cl to [PPh4][Ga(Et)(OTeF5)3] and [CPh3][Ga(Et)(OTeF5)3]. In contrast, Ag[Ga(OTeF5)4] is prepared from AgOTeF5 and GaCl3 and is used as a versatile starting material for further re...


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