bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Dynamic Interaction of n‐Butane with Imidazolium‐Based Ionic Liquids
Authors: Bhuin Radha G. , Winter Leonhard , Lexow Matthias , Maier Florian , Steinrück Hans‐Peter 
Published: May 2020

AbstractThe impact of a reactant from the gas phase on the surface of a liquid and its transfer through this gas/liquid interface are crucial for various concepts applying ionic liquids (ILs) in catalysis. We investigated the first step of the adsorption dynamics of n‐butane on a series of 1‐alkyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide ILs ([CnC1Im][Tf2N]; n=1, 2, 3, 8). Using a supersonic molecular beam in ultra‐high vacuum, the trapping of n‐butane on the frozen ILs was determined as a function of surface temperature, between 90 and 125 K. On the C8‐ and C3‐ILs, n‐butane adsorbs at 90 K with an initial trapping probability of ≈0.89. The adsorption energy increases with increasing length of the IL alkyl chain, whereas the ionic headgroups seem to interact only weakly with n‐butane. The absence of adsorption on the C1‐ and C2‐ILs is attributed to a too short residence time on the IL surface to form nuclei for condensation even at 90 K.
Too little but not too late? Biology of a recently discovered and imperilled freshwater fish in a drying temperate region and comparison with sympatric fishes
Authors: Allen Mark G. , Morgan David L. , Close Paul G. , Beatty Stephen J. 
Published: May 2020

Abstract

Small‐bodied freshwater fishes are commonly overlooked in threatened species management despite being highly imperilled. Before this study, the newly described little pygmy perch (Nannoperca pygmaea) was known from only 0.06 km2 of habitat in a single catchment in south‐western Australia and a lack of knowledge prevented an understanding of its conservation status and priority actions.

The present study determined the distribution, biology, and movement patterns of N. pygmaea and compared these with other small, sympatric percihthyids to assess its conservation status and likely resilience to threatening processes.

The current ‘extent of occurrence' of N. pygmaea was determined to be 3,420 km2 and the ‘area of occupancy' was 10 km2. Nannoperca pygmaea inhabited permanent refuge pools in the main stem of an ephemeral, secondarily salinized catchment where salinities remained <6 ppt during summer.

During winter N. pygmaea undertook a short upstream migration into a seasonally flowing freshwater tributary to serially spawn. The timing of reproduction was partitioned among three sympatric pygmy perches within the austral winter/spring period.

The species qualifies as ‘Endangered' under the IUCN Red List assessment criteria. Its restriction to freshwater refugia within salinized rivers suggests that N. pygmaea may have a limited salinity tolerance similar to the sympatric, threatened Nannatherina balstoni, and that the species is susceptible to prolonged drought, drying of critical baseflow refuges, increasing salinization, and introductions of alien species.

The study serves as an example that small‐bodied freshwater fishes need greater research attention to understand the biological and environmental mechanisms underpinning their decline.
Further evidence of superluminal active galactic nuclei as γ‐ray sources
Authors: Xiao Hubing , Fan Junhui , Rando Riccardo , Zhu Jingtian , Hu Liangjun 
Published: May 2020

AbstractIn our previous work in Xiao et al. (SCPMA, 2019, 62, 129811), we suggested that six superluminal sources could be γ‐ray candidates, and in fact, five of them have been confirmed in the fourth Fermi‐LAT source catalog (4FGL). In this work, based on the 4FGL, we report a sample of 229 Fermi detected superluminal sources (FDSs), including 40 new FDSs and 62 non‐FDSs. Thus, we believe that all superluminal sources should have γ‐ray emissions, and superluminal motion could also be a clue to detect γ‐ray emission from active galactic nuclei. We present a new approach of Doppler factor estimate through the study of the γ‐ray luminosity (Lγ) and of the viewing angle (ϕ).
A comparative analysis of raw and processed Radix Paeoniae Alba samples using HPLC, chemometrics, and antioxidant activity
Authors: You Guangjiao , Li Chenghao , Mao Yingying , Ren Xiaoliang , Liu Yanan , Wang Meng 
Published: May 2020

AbstractRadix Paeoniae Alba (RPA) and its processed products are commonly used in traditional Chinese medicine, but the chaos phenomenon among processed products often occurs. In this study, we used multiple chemometric methods to analyze raw and six different processed products of RPA based on HPLC fingerprinting. Heat map analysis was used to assess the changes in chemical composition. Principal component analysis was used for classification, and the samples were divided into four classes: class 1 (raw, wine‐processed, and vinegar‐processed products), class 2 (bran‐processed and soil‐processed products), class 3 (stir‐fried products), and class 4 (coke products). Further, the orthogonal partial least squares discriminant analysis model was used to obtain chemical markers among different classes. The antioxidant property of RPA is an important factor responsible for its pharmacological effects, and so the antioxidant activity of RPA was also investigated. We measured 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH) and hydroxyl radical scavenging ability, and ferric reducing antioxidant power. The total antioxidant activity follows the order: coke > stir‐fried > soil‐processed > bran‐processed > wine‐processed > raw > vinegar‐processed products. These results suggest that different processing methods affect the chemical composition and antioxidant power of RPA, and thus, different products of RPA should not be mixed.
COVID‐19 complicated by acute myocardial infarction with extensive thrombus burden and cardiogenic shock
Authors: Harari Rafael , Bangalore Sripal , Chang Ernest , Shah Binita 
Published: May 2020

AbstractA patient with coronavirus disease 19 (COVID‐19) developed acute myocardial infarction (AMI) complicated by extensive coronary thrombosis and cardiogenic shock. She underwent percutaneous coronary intervention and placement of a mechanical circulatory support device but subsequently died from shock. This report illustrates the challenges in managing patients with COVID‐19, AMI, and cardiogenic shock.
Electronic Oxide–Metal Strong Interaction (EOMSI)
Authors: Qian Kun , Duan Huimei , Li Yangyang , Huang Weixin 
Published: May 2020

AbstractStrong metal–support interaction of supported metal catalysts is an important concept to describe the effect of metal–support interactions on the structures and catalytic performances of supported metal particles. By using an example of CeOx adlayers supported on Ag nanocrystals, herein a concept of electronic oxide–metal strong interaction (EOMSI) is put forward; this interaction significantly affects the electronic structures of oxide adlayers through metal‐to‐oxide charge transfer. The EOMSI can stabilize oxide adlayers in a low oxidation state under ambient conditions, which individually are not stable; moreover, the oxide adlayers experiencing the EOMSI are resistant to high‐temperature oxidation in air to a certain extent. Such an EOMSI concept helps to generalize the strong influence of oxide–metal interactions on the structures and catalytic performance of oxide/metal inverse catalysts, which have been attracting increasing attention.
Phase Transition and Band Gap Regulation by Halogen Substituents on the Organic Cation in Organic–Inorganic Hybrid Perovskite Semiconductors
Authors: Cao Ying‐Jie , Zhou Lin , He Lei , Shi Ping‐Ping , Ye Qiong , Fu Da‐Wei 
Published: May 2020

AbstractIn the last decade, hybrid materials have received widespread attention. In particular, hybrid lead halide perovskite‐type semiconductors are very attractive owing to their great flexibility in band gap engineering. Here, by using precise molecular modifications, three one‐dimensional perovskite‐type semiconductor materials are designed and obtained: [Me3PCH2X][PbBr3] (X=H, F, and Cl for compounds 1, 2, and 3, respectively). The introduction of a heavier halogen atom (F or Cl) to [Me4P]+ increases the potential energy barrier required for the tumbling motion of the cation, hence achieving the transformation of the phase transition temperature from low temperature (192 K) to room temperature (285 K) and high temperature (402.3 K). Moreover, the optical band gaps reveal a broadening trend with 3.176 eV, 3.215 eV, and 3.376 eV along the H→F→Cl series, which is attributed to the formation of the structural distortion.
Self‐Assembly of Mitochondria‐Targeted Photosensitizer to Increase Photostability and Photodynamic Therapeutic Efficacy in Hypoxia
Authors: Jana Batakrishna , Thomas Ajesh P. , Kim Sangpil , Lee In Seong , Choi Huyeon , Jin Seongeon , Park Soo Ah , Min Seung Kyu , Kim Chaekyu , Ryu Ja‐Hyoung 
Published: May 2020

AbstractThe development of photosensitizers for cancer photodynamic therapy has been challenging due to their low photostability and therapeutic inefficacy in hypoxic tumor microenvironments. To overcome these issues, we have developed a mitochondria‐targeted photosensitizer consisting of an indocyanine moiety with triphenylphosphonium arms, which can self‐assemble into spherical micelles directed to mitochondria. Self‐assembly of the photosensitizer resulted in a higher photostability by preventing free rotation of the indoline ring of the indocyanine moiety. The mitochondria targeting capability of the photosensitizer allowed it to utilize intramitochondrial oxygen. We found that the mitochondria‐targeted photosensitizer localized to mitochondria and induced apoptosis of cancer cells both normoxic and hypoxic conditions through generation of ROS. The micellar self‐assemblies of the photosensitizer were further confirmed to selectively localize to tumor tissues in a xenograft tumor mouse model through passive targeting and showed efficient tumor growth inhibition.
London Dispersion and Hydrogen‐Bonding Interactions in Bulky Molecules: The Case of Diadamantyl Ether Complexes
Authors: Quesada Moreno María Mar , Pinacho Pablo , Pérez Cristóbal , Šekutor Marina , Schreiner Peter R. , Schnell Melanie 
Published: May 2020

AbstractDiadamantyl ether (DAE, C20H30O) represents a good model to study the interplay between London dispersion and hydrogen‐bond interactions. By using broadband rotational spectroscopy, an accurate experimental structure of the diadamantyl ether monomer is obtained and its aggregates with water and a variety of aliphatic alcohols of increasing size are analyzed. In the monomer, C−H⋅⋅⋅H−C London dispersion attractions between the two adamantyl subunits further stabilize its structure. Water and the alcohol partners bind to diadamantyl ether through hydrogen bonding and non‐covalent Owater/alcohol⋅⋅⋅H−CDAE and C−Halcohol⋅⋅⋅H−CDAE interactions. Electrostatic contributions drive the stabilization of all the complexes, whereas London dispersion interactions become more pronounced with increasing size of the alcohol. Complexes with dominant dispersion contributions are significantly higher in energy and were not observed in the experiment. The results presented herein shed light on the first steps of microsolvation and aggregation of molecular complexes with London dispersion energy donor (DED) groups and the kind of interactions that control them.
Tetrahydroimidazo[1,2‐a]pyrazine Derivatives: Synthesis and Evaluation as Gαq‐Protein Ligands
Authors: Küppers Jim , Benkel Tobias , Annala Suvi , Kimura Kenichi , Reinelt Lisa , Fleischmann Bernd K. , Kostenis Evi , Gütschow Michael 
Published: May 2020

AbstractThe 5,6,7,8‐tetrahydroimidazo[1,2‐a]pyrazine derivative BIM‐46174 and its dimeric form BIM‐46187 (1) are heterocyclized dipeptides that belong to the very few cell‐permeable compounds known to preferentially silence Gαq proteins. To explore the chemical space of Gαq inhibitors of the BIM chemotype, a combinatorial approach was conducted towards a library of BIM molecules. This library was evaluated in a second messenger‐based fluorescence assay to analyze the activity of Gαq proteins through the determination of intracellular myo‐inositol 1‐phosphate. Structure–activity relationships were deduced and structural requirements for biological activity obtained, which were (i) a redox reactive thiol/disulfane substructure, (ii) an N‐terminal basic amino group, (iii) a cyclohexylalanine moiety, and (iv) a bicyclic skeleton. Active compounds exhibited cellular toxicity, which was investigated in detail for the prototypical inhibitor 1. This compound affects the structural cytoskeletal dynamics in a Gαq/11‐independent manner.
Resonance Assisted Hydrogen Bonding Phenomenon Unveiled through Both Experiments and Theory: A New Family of Ethyl N‐Salicylideneglycinate Dyes
Authors: Shapenova Dinara S. , Shiryaev Alexey A. , Bolte Michael , Kukułka Mercedes , Szczepanik Dariusz W. , Hooper James , Babashkina Maria G. , Mahmoudi Ghodrat , Mitoraj Mariusz P. , Safin Damir A. 
Published: May 2020

AbstractExtensive experimental and theoretical investigations are reported on the nature of resonance‐assisted hydrogen bonding phenomenon (RAHB) and its influence on photophysical properties of the newly designed dyes differing in donor–acceptor properties, namely ethyl N‐salicylideneglycinate (1), ethyl N‐(5‐methoxysalicylidene)glycinate (2), ethyl N‐(5‐bromosalicylidene)glycinate (3) and ethyl N‐(5‐nitrosalicylidene)glycinate (4). All compounds are thermochromic in the solid state and they contain a typical intramolecular O−H⋅⋅⋅N hydrogen bond formed between the hydroxyl hydrogen atom and the imine nitrogen atom, yielding the enol form in the solid state. It is unveiled, that the magnitude of RAHB effect fine tunes the strength of the O−H⋅⋅⋅N bonding and accordingly the relative populations of the enol, cis‐keto and trans‐keto forms leading to variation of the photophysical properties of 1–4. It is determined, that the electron‐withdrawing NO2 in 4 amplifies the most RAHB effect causing the breaking of the O−H⋅⋅⋅N hydrogen bond and accordingly formation of the dominant cis‐keto isomer in both the solid state and EtOH. To this end, the UV/Vis spectra of 1–3 in EtOH revealed the exclusive presence of the enol form, while the prevalent contribution of the cis‐keto form was found for 4. Furthermore, only compound 4 is emissive in the solid state in ambient condition due to dual emission arising from the cis‐keto* and trans‐keto* forms, while 2 was found to be highly emissive in EtOH. It is revealed qualitatively and quantitatively, based on the ETS‐NOCV charge and energy decomposition scheme and the EDDB population‐based method, that RAHB is strongly a non‐local phenomenon based on electrons pumping or sucking through both the π‐ and σ‐channels, which accordingly exerts chemical bonding changes at both the phenyl ring and predominantly a distant O−H⋅⋅⋅N area.
An Air‐ and Water‐Stable Hydrogen‐Bond‐Donor Catalyst for the Enantioselective Generation of Quaternary Carbon Stereocenters by Additions of Substituted Cyanoacetate Esters to Acetylenic Esters
Authors: Luu Quang H. , Gladysz John A. 
Published: May 2020

AbstractThe chiral enantiopure cobalt(III) complex Δ‐[Co((S,S)‐dpen)3]3+ 2Cl−B(C6F5)4− (Δ‐(S,S)‐23+ 2Cl−B(C6F5)4−; dpen=1,2‐diphenylethylenediamine) is an effective catalyst, together with pyridine (10 mol % each), for enantioselective additions of substituted cyanoacetate esters NCCH(R)CO2R′ to acetylenic esters R′′C≡CCO2R′′′. In the resulting adducts NC(R′O2C)C(R)CR′′C=CHCO2R′′′, C=C isomers in which the CO2R′′′ moiety is trans to the new carbon–carbon bond dominate (avg. ratio 98:2). These are obtained in 70–98 % ee (avg. 86 %; data for optimum R′ and R′′′), as determined by 1H NMR with the chiral solvating agent Λ‐(S,S)‐23+ 2I−B(3,5‐C6H3(CF3)2)4−. NMR experiments show that the cyanoacetate and acetylenic esters and pyridine can hydrogen bond to certain NH groups of the catalyst. Rates are zero order in the cyanoacetate and acetylenic esters as well as the catalyst, and implications are discussed.
Hydrogen‐Bond Catalysis of Imine Exchange in Dynamic Covalent Systems
Authors: Schaufelberger Fredrik , Seigel Karolina , Ramström Olof 
Published: May 2020

AbstractThe reversibility of imine bonds has been exploited to great effect in the field of dynamic covalent chemistry, with applications such as preparation of functional systems, dynamic materials, molecular machines, and covalent organic frameworks. However, acid catalysis is commonly needed for efficient equilibration of imine mixtures. Herein, it is demonstrated that hydrogen bond donors such as thioureas and squaramides can catalyze the equilibration of dynamic imine systems under unprecedentedly mild conditions. Catalysis occurs in a range of solvents and in the presence of many sensitive additives, showing moderate to good rate accelerations for both imine metathesis and transimination with amines, hydrazines, and hydroxylamines. Furthermore, the catalyst proved simple to immobilize, introducing both reusability and extended control of the equilibration process.
Modeling the Reaction of Carboxylic Acids and Isonitriles in a Self‐Assembled Capsule
Authors: Daver Henrik , Rebek Julius , Himo Fahmi 
Published: May 2020

AbstractQuantum chemical calculations were used to study the reaction of carboxylic acids with isonitriles inside a resorcinarene‐based self‐assembled capsule. Experimentally, it has been shown that the reactions between p‐tolylacetic acid and n‐butyl isonitrile or isopropyl isonitrile behave differently in the presence of the capsule compared both with each other and also with their solution counterparts. Herein, the reasons for these divergent behaviors are addressed by comparing the detailed energy profiles for the reactions of the two isonitriles inside and outside the capsule. An energy decomposition analysis was conducted to quantify the different factors affecting the reactivity. The calculations reproduce the experimental findings very well. Thus, encapsulation leads to lowering of the energy barrier for the first step of the reaction, the concerted α‐addition and proton transfer, which in solution is rate‐determining, and this explains the rate acceleration observed in the presence of the capsule. The barrier for the final step of the reaction, the 1,3 O→N acyl transfer, is calculated to be higher with the isopropyl substituent inside the capsule compared with n‐butyl. With the isopropyl substituent, the transition state and the product of this step are significantly shorter than the preceding intermediate, and this results in energetically unfavorable empty spaces inside the capsule, which cause a higher barrier. With the n‐butyl substituent, on the other hand, the carbon chain can untwine and hence uphold an appropriate guest length.
Electrophilic Chlorine from Chlorosulfonium Salts: A Highly Chemoselective Reduction of Sulfoxides
Authors: Acosta‐Guzmán Paola , Mahecha‐Mahecha Camilo , Gamba‐Sánchez Diego 
Published: May 2020

AbstractHerein, we describe a selective late‐stage deoxygenation of sulfoxides based on a novel application of chlorosulfonium salts and demonstrate a new process using these species generated in situ from sulfoxides as the source of electrophilic chlorine. The use of highly nucleophilic 1,3,5‐trimethoxybenzene (TMB) as the reducing agent is described for the first time and applied in the deoxygenation of simple and functionalized sulfoxides. The method is easy to handle, economic, suitable for gram‐scale operations, and readily applied for poly‐functionalized molecules, as demonstrated with more than 45 examples, including commercial medicines and analogues. We also report the results of competition experiments that define the more reactive sulfoxide and we present a mechanistic proposal based on substrate and product observations.
Synthesis of Nitro‐Aryl Functionalised 4‐Amino‐1,8‐Naphthalimides and Their Evaluation as Fluorescent Hypoxia Sensors
Authors: Adair Liam D. , Trinh Natalie , Vérité Pauline M. , Jacquemin Denis , Jolliffe Katrina A. , New Elizabeth J. 
Published: May 2020

AbstractFluorescent sensors are a vital research tool, enabling the study of intricate cellular processes in a sensitive manner. The design and synthesis of responsive and targeted probes is necessary to allow such processes to be interrogated in the cellular environment. This remains a challenge, and requires methods for functionalisation of fluorophores with multiple appendages for sensing and targeting groups. Methods to synthesise more structurally complex derivatives of fluorophores will expand their potential scope. Most known 4‐amino‐1,8‐naphthalimides are only functionalised at imide and 4‐positions, and structural modifications at additional positions will increase the breadth of their utility as responsive sensors. In this work, methods for the incorporation of a hypoxia sensing group to 4‐amino‐1,8‐naphthalimide were evaluated. An intermediate was developed that allowed us to incorporate a sensing group, targeting group, and ICT donor to the naphthalimide core in a modular fashion. Synthetic strategies for attaching the hypoxia sensing group and how they affected the fluorescence of the naphthalimide were evaluated by photophysical characterisation and time‐dependent density functional theory. An extracellular hypoxia probe was then rationally designed that could selectively image the hypoxic and necrotic region of tumour spheroids. Our results demonstrate the versatility of the naphthalimide scaffold and expand its utility. This approach to probe design will enable the flexible, efficient generation of selective, targeted fluorescent sensors for various biological purposes.
Co Single‐Atom Catalysts Boost Chemiluminescence
Authors: Ouyang Hui , Zhang Lvxia , Jiang Shan , Wang Wenwen , Zhu Chengzhou , Fu Zhifeng 
Published: May 2020

AbstractCo single‐atom catalysts (SACs) with good aqueous solubility and abundant labelling functional groups were prepared in Co/Fe bimetallic metal‐organic frameworks by a facile solvothermal method without high‐temperature calcination. In contrast to traditional chemiluminescence (CL) catalysts, Co SACs accelerated decomposition of H2O2 to produce a large amount of singlet oxygen (1O2) rather than superoxide (O2.−) and hydroxyl radical (OH.). They were found to dramatically enhance the CL emission of the luminol‐H2O2 reaction by 1349 times, and, therefore, were employed as very sensitive signal probes for conducting CL immunoassay of cardiac troponin I. The detection limit of the target analyte was as low as 3.3 pg mL−1. It is the first time that employment of SACs for boosting CL reactions has been validated. The Co SACs can also be employed to trace other biorecognition events with high sensitivity.
Photoredox‐Catalyzed Addition of Carbamoyl Radicals to Olefins: A 1,4‐Dihydropyridine Approach
Authors: Cardinale Luana , Konev Mikhail O. , Jacobi von Wangelin Axel 
Published: May 2020

AbstractFunctionalization with C1‐building blocks are key synthetic methods in organic synthesis. The low reactivity of the most abundant C1‐molecule, carbon dioxide, makes alternative carboxylation reactions with CO2‐surrogates especially important. We report a photoredox‐catalyzed protocol for alkene carbamoylations. Readily accessible 4‐carboxamido‐Hantzsch esters serve as convenient starting materials that generate carbamoyl radicals upon visible light‐mediated single‐electron transfer. Addition to various alkenes proceeded with high levels of regio‐ and chemoselectivity.