pinecone/core-2020-05-10-deduplication huggingface dataset:
Influence of Equatorial CH⋅⋅⋅ O Interactions on Secondary Kinetic Isotope Effects for Methyl Transfer

Open Access articleDFT calculations for methyl cation complexed within a constrained cage of water molecules permit the controlled manipulation of the “axial” donor/acceptor distance and the “equatorial” distance to hydrogen-bond acceptors. The kinetic isotope effect k(CH3)/k(CT3) for methyl transfer within a cage with a short axial distance becomes less inverse for shorter equatorial C⋅⋅⋅O distances: a decrease of 0.5 Å results in a 3 % increase at 298 K. Kinetic isotope effects in AdoMet-dependent methyltransferases may be m∧odulated by CH⋅⋅⋅O hydrogen bonding, and factors other than axial compression may contribute, at least partially, to recently reported isotope-effect variations for catechol-O-methyltransferase and its mutant structures
Photoelectrochemical H$_{2}$ Evolution with a Hydrogenase Immobilized on a TiO$_{2}$-Protected Silicon Electrode

The integration of enzymes with semiconductors enables the photoelectrochemical characterization of electron transfer processes at highly active and well-defined catalytic sites on a light-harvesting electrode surface. Here, we report the integration of a hydrogenase on a TiO$_{2}$-coated p-Si photocathode for the photoreduction of protons to H$_{2}$. The immobilized hydrogenase exhibits activity on Si attributable to a bifunctional TiO$_{2}$ layer, which protects the Si electrode from oxidation and acts as biocompatible support layer for the productive adsorption of the enzyme. The p-Si|TiO$_{2}$|hydrogenase photocathode displays the visible-light driven production of H$_{2}$ at an energy-storing, positive electrochemical potential and an essentially quantitative faradaic efficiency. We have therefore established a widely applicable platform to wire redox enzymes in an active configuration on a p-type semiconductor photocathode through the engineering of the enzyme-materials interface.This work was supported by the Intra-European Marie-Curie fellowship (to CYL), the BBSRC (BB/K010220/1), the Christian Doppler Research Association (Austrian Federal Ministry of Science, Research and Economy, and the National Foundation for Research, Technology and Development) and the OMV Group (to ER).This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/anie.20151182
Benzotrithiophene-Based Hole-Transporting Materials for 18.2% Perovskite Solar Cells

New star-shaped benzotrithiophene (BTT)-based hole-transporting materials (HTM) BTT-1, BTT-2 and BTT-3 have been obtained through a facile synthetic route by crosslinking triarylamine-based donor groups with a benzotrithiophene (BTT) core. The BTT HTMs were tested on solution-processed lead trihalide perovskite-based solar cells.Power conversion efficiencies in the range of 16% to 18.2% were achieved under AM 1.5 sun with the three derivatives. These values are comparable to those obtained with todays most commonly used HTM spiro-OMeTAD, which point them out as promising candidates to be used as readily available and cost-effective alternatives in perovskite solar cells (PSCs)
Heterologous Production of Fungal Maleidrides Reveals the Cryptic Cyclization Involved in their Biosynthesis

Fungal maleidrides are an important family of bioactive secondary metabolites that consist of 7, 8, or 9-membered carbocycles with one or two fused maleic anhydride moieties. The biosynthesis of byssochlamic acid (a nonadride) and agnestadride A (a heptadride) was investigated through gene disruption and heterologous expression experiments. The results reveal that the precursors for cyclization are formed by an iterative highly reducing fungal polyketide synthase supported by a hydrolase, together with two citrate-processing enzymes. The enigmatic ring formation is catalyzed by two proteins with homology to ketosteroid isomerases, and assisted by two proteins with homology to phosphatidylethanolamine-binding proteins. Ring cycle: The enzymes involved in the cyclization of the maleidride family of bioactive fungal natural products, including agnestadride A and byssochlamic acid, were identified. These previously unknown proteins show homology to ketosteroid isomerases (KI-like) and phosphatidylethanolamine-binding proteins (PEBP-like).BBSRCSyngent
Dibenzo[a,j]phenazine-cored donor-acceptor-donor compounds as green-to-red/NIR thermally activated delayed fluorescence organic light emitters.

A new family of thermally activated delayed fluorescence (TADF) emitters based on U-shaped D-A-D architecture with a novel accepting unit has been developed. All investigated compounds have small singlet-triplet energy splitting (E-ST) ranging from 0.02 to 0.20eV and showed efficient TADF properties. The lowest triplet state of the acceptor unit plays the key role in the TADF mechanism. OLEDs fabricated with these TADF emitters achieved excellent efficiencies up to 16% external quantum efficiency (EQE)
An Iodine-Vapour-Induced Cyclization in a Crystalline Molecular Flask

A vapour-induced cyclisation has been demonstrated in the hosted environment of a crystalline molecular flask (CMF), within which 1,8-bis(2-phenylethynyl)naphthalene (bpen), a diarenynyl system primed for cyclisation, has been exposed to iodine vapour to yield the corresponding indeno[2,1-α]phenalene species. The cyclisation process, unique in its vapour-induced, solvent-free nature, has been followed spectroscopically, and found to occur concurrently with the displacement of lattice solvent for molecular iodine in CMF·0.75bpen·2.25CHCl3·H2O. The cyclisation occurs under mild conditions and without the need to suspend the crystals in solvent. The ability of CMFs to host purely gas-induced reactions is further highlighted by a subsequent, sequential, oxidation reaction of the cyclised 7-iodo-12-phenylindeno[2,1-α]phenalene (ipp) with molecular oxygen derived from air, yielding 12-hydroxy-7-iodo-2-phenylindeno[2,1-α]phenalen-1(12H)-one (hipp)
Enzymatic macrocyclization of 1,2,3-triazole peptide mimetics

This work was supported by the European Research Council (339367), UK Biotechnology and Biological Sciences Research Council (K015508/1), the Wellcome Trust (TripleTOF 5600 mass spectrometer (094476), the MALDI TOF-TOF Analyser (079272AIA), 700 NMR) and the EPSRC UK National Mass Spectrometry Facility at Swansea University. J.H.N. is a Royal Society Wolfson Merit Award Holder and 1000 talent scholar at Sichuan University.The macrocyclization of linear peptides is very often accompanied by significant improvements in their stability and biological activity. Many strategies are available for their chemical macrocyclization, however, enzyme-mediated methods remain of great interest in terms of synthetic utility. To date, known macrocyclization enzymes have been shown to be active on both peptide and protein substrates. Here we show that the macrocyclization enzyme of the cyanobactin family, PatGmac, is capable of macrocyclizing substrates with one, two, or three anti-1,2,3-triazole moieties. The introduction of non-peptidic scaffolds into macrocycles is highly desirable in tuning the activity and physical properties of peptidic macrocycles. We have isolated and fully characterized nine non-natural triazole-containing cyclic peptides, a further ten molecules are also synthesized. PatGmac has now been shown to be an effective and versatile tool for the ring closure by peptide bond formation.PostprintPublisher PDFPeer reviewe
Quinine-Catalyzed Asymmetric Synthesis of 2,2’-Binaphthol-Type Biaryls under Mild Reaction Conditions

Simple quinine as an organocatalyst mediates the\ud
addition of various naphthols to halogenated quinones to\ud
afford non-C2-symmetrical, axially chiral biaryl products,\ud
which are promising compounds as chiral ligands and organocatalysts.\ud
The rotational barrier required to have two distinct\ud
atropisomers has been evaluated in the products generated\ud
from the addition of naphthols to various quinones by means\ud
of DFT calculations and HPLC. The use of halogenated\ud
quinones as reagents was necessary to have configurationally\ud
stable enantiomeric products which can be obtained in good\ud
yield and stereoselectivity. These compounds have also been\ud
prepared in gram quantities and recrystallized to near enantiopurity
Highly strained heterocycles constructed from boron-boron multiple bonds and heavy chalcogens

H.B. acknowledges the generous financial support provided by an ERC Advanced Grant.The reactions of a diborene with elemental selenium or tellurium are shown to afford a diboraselenirane or diboratellurirane, respectively. These reactions are reminiscent of the sequestration of sub-valent oxygen and nitrogen in the formation of oxiranes and aziridines; however, such reactivity is not known between alkenes and the heavy chalcogens. While carbon is too electronegative to affect the reduction of elements of lower relative electronegativity, the highly reducing nature of the B=B double bond enables reactions with Se0 and Te0. The capacity of multiple bonds between boron to donate electron density is highlighted in reactions where diborynes behave as nucleophiles, attacking one of the two Te atoms of diaryltellurides, forming salts consisting of diboratellurenium cations and aryltelluride anions.PostprintPeer reviewe
Highly Enantioselective Iridium-Catalyzed Hydrogenation of Cyclic Enamides

The MaxPHOX-Ir catalyst system provided the highest selectivity ever reported for the redn. of cyclic enamides derived from α- and β-tetralones. This result indicates that iridium catalysts are also proficient in reducing alkenes bearing metal-coordinating groups. In the present system, selectivity was pressure-dependent: in most cases, a decrease in the H2 pressure to 3 bar resulted in an increase in enantioselectivity. Moreover, the process can be carried out in environmentally friendly solvents, such as methanol and Et acetate, with no loss of selectivity
Transfer of Electrophilic NH Using Convenient Sources of Ammonia. Direct Synthesis of N–H Sulfoximines from Sulfoxides

© 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.A new system for NH transfer is developed for the preparation of sulfoximines, which are emerging as valuable motifs for drug discovery. The protocol employs readily available sources of nitrogen without the requirement for either preactivation or for metal catalysts. Mixing ammonium salts with diacetoxyiodobenzene directly converts sulfoxides into sulfoximines. This report describes the first example of using of ammonia sources with diacetoxyiodobenzene to generate an electrophilic nitrogen center. Control and mechanistic studies suggest a short-lived electrophilic intermediate, which is likely to be PhINH or PhIN+
A Method for Detecting Circulating Tumor Cells Based on the Measurement of Single-Cell Metabolism in Droplet-Based Microfluidics

The number of circulating tumor cells (CTCs) in blood is strongly correlated with the progress of metastatic cancer. Current methods to detect CTCs are based on immunostaining or discrimination of physical properties. Herein, a label-free method is presented exploiting the abnormal metabolic behavior of cancer cells. A single-cell analysis technique is used to measure the secretion of acid from individual living tumor cells compartmentalized in microfluidically prepared, monodisperse, picoliter (pL) droplets. As few as 10 tumor cells can be detected in a background of 200 000 white blood cells and proof-of-concept data is shown on the detection of CTCs in the blood of metastatic patients
First step towards a Devil's Staircase in Spin Crossover materials First step towards Devil's Staircase in Spin Crossover materials

International audienceThe devil is in the detail: Periodic and aperiodic spin-state concentration waves form during “Devil’s staircase”-type spincrossover in a new bimetallic 2D coordination polymer {Fe[(Hg(SCN)3)2](4,4’-bipy)2}n.The unprecedented bimetallic 2D coordination polymer {Fe[(Hg(SCN)3)2](4,4’-bipy)2}n exhibits a thermal high-spin (HS)$low-spin (LS) staircase-like conversion characterized by a multi-step dependence of the HS molar fraction gHS. Between the fully HS (gHS=1) and LS (gHS=0) phases, two steps associated with different ordering appear in terms of spin-state concentration waves (SSCW). On the gHS=0.5 step, a periodic SSCW forms with a HS-LS-HS-LS sequence. On the gHS=0.34 step, the 4D superspace crystallography structural refinement reveals an aperiodic SSCW, with a HS-LS sequence incommensurate with the molecular lattice. The formation of these different long-range spatially ordered structures of LS and HS states during the multi-step spin-crossover is discussed within the framework of “Devil's staircase”-type transitions. Spatially modulated phases are known in various types of materials but are uniquely related to molecular HS/LS bistability in this case
An Air-Stable Semiconducting Polymer Containing Dithieno[3,2-b:2′,3′-d]arsole

© 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.Arsole-containing conjugated polymers are a practically unexplored class of materials despite the high interest in their phosphole analogues. Herein we report the synthesis of the first dithieno[3,2-b;2′,3′-d]arsole derivative, and demonstrate that it is stable to ambient oxidation in its +3 oxidation state. A soluble copolymer is obtained by a palladium-catalyzed Stille polymerization and demonstrated to be a p-type semiconductor with promising hole mobility, which was evaluated by field-effect transistor measurements
Coupling of the Decarboxylation of 2-Cyano-2-phenylpropanoic Acid to Large-Amplitude Motions: A Convenient Fuel for an Acid-Base-Operated Molecular Switch

The decarboxylation of 2-cyano-2-phenylpropanoic acid is fast and quantitative when carried out in the presence of 1 molar equivalent of a [2]catenane composed of two identical macrocycles incorporating a 1,10-phenanthroline unit in their backbone. When decarboxylation is over, all of the catenane molecules have experienced large-amplitude motions from neutral to protonated catenane, and back again to the neutral form, so that they are ready to perform another cycle. This study provides the first example of the cyclic operation of a molecular switch at the sole expenses of the energy supplied by the substrate undergoing chemical transformation, without recourse to additional stimuli
Bismuth-Based Coordination Polymers with Efficient Aggregation-Induced Phosphorescence and Reversible Mechanochromic Luminescence

Two bismuth coordination polymers (CPs), (TBA)[BiBr4(bp4mo)] (TBA=tetrabutylammonium) and [BiBr3(bp4mo)2], which are based on the rarely used simple ditopic ligand N-oxide-4,4′-bipyridine (bp4mo), show mechanochromic luminescence (MCL). High solid-state phosphorescence quantum yields of up to 85 % were determined for (TBA)[BiBr4(bp4mo)] (λem=540 nm). Thorough investigations of the luminescence properties combined with DFT and TDDFT calculations revealed that the emission is due to aggregation-induced phosphorescence (AIP). Upon grinding, both samples became amorphous, and their luminescence changed from yellow to orange and red, respectively. Heating or exposure to water vapor led to the recovery of the initial luminescence. These materials are the first examples of mechanochromic phosphors based on bismuth(III)
Dizinc Lactide Polymerization Catalysts: Hyper-Activity by Control of Ligand Conformation and Metallic Cooperativity

© 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.Understanding how to moderate and improve catalytic activity is critical to improving degradable polymer production. Here, di- and monozinc catalysts, coordinated by bis(imino)diphenylamido ligands, show remarkable activities and allow determination of the factors controlling performance. In most cases, the dizinc catalysts significantly out-perform the monozinc analogs. Further, for the best dizinc catalyst, the ligand conformation controls activity: the catalyst with “folded” ligand conformation shows turnover frequency (TOF) values up to 60 000 h−1 (0.1 mol % loading, 298 K, [LA]=1 m), whilst that with a “planar” conformation is much slower, under similar conditions (TOF=30 h−1). Dizinc catalysts also perform very well under immortal conditions, showing improved control, and are able to tolerate loadings as low as 0.002 mol % whilst conserving high activity (TOF=12 500 h−1)
Quantification of stereochemical communication in metal–organic assemblies.

The derivation and application of a statistical mechanical model to quantify stereochemical communication in metal–organic assemblies is reported. The factors affecting the stereochemical communication within and between the metal stereocenters of the assemblies were experimentally studied by optical spectroscopy and analyzed in terms of a free energy penalty per “incorrect” amine enantiomer incorporated, and a free energy of coupling between stereocenters. These intra- and inter-vertex coupling constants are used to track the degree of stereochemical communication across a range of metal–organic assemblies (employing different ligands, peripheral amines, and metals); temperature-dependent equilibria between diastereomeric cages are also quantified. The model thus provides a unified understanding of the factors that shape the chirotopic void spaces enclosed by metal–organic container molecules
Hydrogen-Bond Cooperativity in Formamide2–Water: A Model for Water-Mediated Interactions

Producción CientíficaThe rotational spectrum of formamide2-H2O formed in a supersonic jet has been characterized by Fourier transform microwave spectroscopy. This adduct provides a simple model of water mediated interaction involving the amide linkages, as occur in protein folding or amide association processes, showing the interplay between self-association and solvation. Mono-substituted 13C, 15N, 18O and 2H isotopologues have been observed to investigate the structure. The adduct forms an almost planar three body sequential cycle. The two formamide molecules link on one side through an N-H···O hydrogen bond and on the other side through a water-mediated interaction with the formation of C=O···H-O and O···H-N hydrogen bonds. The analysis of the quadrupole coupling effects due to the presence of two 14N-nuclei reveal the subtle inductive forces associated to cooperative hydrogen bonding. These forces are involved in the changes detected in the C=O and C-N bond distances with respect to bare formamide.2018-03-03Ministerio de Economía, Industria y Competitividad (CTQ2013-40717-P)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA334U14
Sterically demanding oxidative amidation of alpha-substituted malononitriles with amines using O2

An efficient amidation method between readily available 1,1-dicyanoalkanes and chiral or non-chiral amines was realized simply with molecular oxygen and a carbonate base. This oxidative protocol can be applied to both sterically and electronically challenging substrates in a highly chemoselective, practical, and rapid manner. The use of cyclopropyl and thioether substrates support the radical formation of alpha-peroxy malononitrile species, which can cyclize to dioxiranes that can monooxygenate malononitrile alpha-carbanions to afford activated acyl cyanides capable of reacting with amine nucleophiles
A bimetallic 1,1’-bis(boratabenzene) complex: unprecedented intramolecular metal-metal communication through a B-B bond

We report the synthesis of the first 1,1’-bis (boratabenzene) species by tetrabromodiborane(4) induced ring-expansion reactions of cobaltocene. Six equivalents of cobaltocene are required as the species plays the dual role of reagent as well as reductant to yield [{(η5-C5H5)Co}2{μ:η6,η6-(BC5H5)2}]. X-ray crystallographic analysis shows that the compound consists of coplanar BC5H5 rings which are coordinated on opposite faces to two cyclopentadienyl cobalt moieties, resulting in a trans-configured bimetallic complex. The formally dianionic bis(boratabenzene) moiety with a boron-boron single bond can be viewed as a symmetric dimer of the parent boratabenzene anion as well as the first example of a diboron analogue of biphenyl. The solution electrochemistry of the bimetallic complex shows four stepwise redox events, indicating significant intramolecular interaction between the cobalt ions across the 1,1’-bis(boratabenzene) unit. The magnetic properties, as investigated by variable-temperature SQUID magnetometry, reveal weak intramolecular antiferromagnetic interactions (J = −6.0 cm−1). Density Functional Theory calculations support the experimental results and add insights into the various electronic states of the complex
Simultaneous identification of spectral properties and sizes of multiple particles in solution with subnanometer resolution

We report an unsurpassed solution characterization technique based on analytical ultracentrifugation, which demonstrates exceptional potential for resolving particle sizes in solution with sub-nm resolution. We achieve this improvement in resolution by simultaneously measuring UV/Vis spectra while hydrodynamically separating individual components in the mixture. By equipping an analytical ultracentrifuge with a novel multi-wavelength detector, we are adding a new spectral discovery dimension to traditional hydrodynamic characterization, and amplify the information obtained by orders of magnitude. We demonstrate the power of this technique by characterizing unpurified CdTe nanoparticle samples, avoiding tedious and often impossible purification and fractionation of nanoparticles into apparently monodisperse fractions. With this approach, we have for the first time identified the pure spectral properties and band-gap positions of discrete species present in the CdTe mixture.Max-Planck Society; BASF SE, Ludwigshafen; National Institutes of Health (RR022200); NSF (ACI-1339649); National Science Foundation (TG-MCB070039N); DFG ("PE 427/28-1"
Light-Driven Electron Accumulation in a Molecular Pentad

Accumulation and temporary storage of redox equivalents with visible light as an energy input is of pivotal importance for artificial photosynthesis because key reactions, such as CO2 reduction or water oxidation, require the transfer of multiple redox equivalents. We report on the first purely molecular system, in which a long-lived charge-separated state (τ≈870 ns) with two electrons accumulated on a suitable acceptor unit can be observed after excitation with visible light. Importantly, no sacrificial reagents were employed
Dissecting Bottromycin Biosynthesis Using Comparative Untargeted Metabolomics

Bottromycin A$_{2}$ is a structurally unique ribosomally synthesized and post-translationally modified peptide (RiPP) that possesses potent antibacterial activity towards multidrug-resistant bacteria. The structural novelty of bottromycin stems from its unprecedented macrocyclic amidine and rare β-methylated amino acid residues. The N-terminus of a precursor peptide (BtmD) is converted into bottromycin A$_{2}$ by tailoring enzymes encoded in the btm gene cluster. However, little was known about key transformations in this pathway, including the unprecedented macrocyclization. To understand the pathway in detail, an untargeted metabolomic approach that harnesses mass spectral networking was used to assess the metabolomes of a series of pathway mutants. This analysis has yielded key information on the function of a variety of previously uncharacterized biosynthetic enzymes, including a YcaO domain protein and a partner protein that together catalyze the macrocyclization.This work was supported by a BBSRC studentship (W.J.K.C.), BBSRC grant BB/M003140/1 (A.W.T. and J.S-A), a Royal Society University Research Fellowship (A.W.T.), and by the BBSRC MET ISP grant to the John Innes Centre.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/anie.20160430