bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water Desorption Kinetics from Alumina Supported Copper Studied by FTIR Spectroscopy
Authors: Wokaun A. , Jobson E. , Baiker A. 
Published: March 2014

AbstractThe desorption of water from an alumina‐supported copper catalyst has been followed by FTIR spectroscopy. On the catalyst, an exponential decrease of the 2400 cm−1 (O‐D stretching) absorption is observed subsequent to loading of the sample with a D2O pulse. The rates and activation energies of desorption are found to be different in N2 and H2 carrier gases. On the pure alumina support the desorption is non‐exponential, and is well described by a Temkin‐type desorption kinetics: A distribution of sites, which are characterized by different desorption enthalpies, are contributing to the broad O‐D stretching band. This is evidenced by different desorption rates for various parts of the band.
Insights into the Organocatalyzed Synthesis of Urethanes in Supercritical Carbon Dioxide: An In Situ FTIR Spectroscopic Kinetic Study
Authors: Smith Christopher A. , Cramail Henri , Tassaing Thierry 
Published: March 2014

AbstractThe kinetics of urethane (carbamate) formation in supercritical CO2 (scCO2) has been studied by in situ FTIR spectroscopy by using the reaction between n‐butanol and toluene‐2,4‐diisocyanate as a model for the synthesis of polyurethanes. We have evaluated the efficiency of different organocatalysts for this transformation to eliminate the need for potentially toxic organotin compounds. Bicyclic guanidines and amidines (7‐methyl‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene) lead to a significant acceleration of the reaction rate, but we found that their activity in scCO2 is reduced compared to reactions in conventional media because of the formation of guanidinium or amidinium alkylcarbonate salts. In scCO2, these catalysts are also sensitive to the presence of water and can lead to the formation of allophanate or isocyanurate byproducts. On the other hand, we have shown that catalysis with amine N‐oxides (N‐methylmorpholine‐N‐oxide) is suited to the scCO2 medium.
Direct Electrochemical Tyrosinase Biosensor based on Mesoporous Carbon and Co3O4 Nanorods for the Rapid Detection of Phenolic Pollutants
Authors: Wang Xue , Lu Xianbo , Wu Lidong , Chen Jiping 
Published: March 2014

AbstractA novel tyrosinase (Tyr) biosensor based on a graphitized ordered mesoporous carbon/cobaltosic oxide nanorod (GMC/Co3O4) nanocomposite is developed for the rapid detection of phenolic pollutants. By applying the GMC/Co3O4 nanocomposite as an enzyme immobilization matrix, rapid direct electron transfer between Tyr and the electrode is achieved. The biosensor exhibits a wide linear response for catechol, ranging from 5.0×10−8 to 1.3×10−5 M, with a limit of detection down to 25 nM and a response time of less than 2 s. The sensitivity of the biosensor based on the GMC/Co3O4 nanocomposite (6.4 A M−1 cm−2) is higher than that of the biosensor based on GMC (5.0 A M−1 cm−2) or Co3O4 (3.5 A M−1 cm−2), which can be attributed to the synergistic effect of the GMC/Co3O4 nanocomposite. The biosensor is further used to systematically detect mixed phenolic samples (phenol, catechol, m‐cresol, p‐cresol, and 4‐chlorophenol) and real water samples. The biosensor‐based detection results for river water and tap water samples show outstanding average recovery (92.2–103.3 %) and relative standard deviations (0.9–7.8 %). In comparison with the conventional spectrophotometric method, the biosensor method is more rapid, sensitive, accurate, and convenient. Furthermore, the detection limit of the biosensor method is about 20 times lower than that of the spectrophotometric method. This novel biosensor is proven to be a promising alternative tool for the rapid and on‐site monitoring of environmental phenolic pollutants.
Plant Antimicrobial Peptides Snakin‐1 and Snakin‐2: Chemical Synthesis and Insights into the Disulfide Connectivity
Authors: Harris Paul W. R. , Yang Sung‐Hyun , Molina Antonio , López Gemma , Middleditch Martin , Brimble Margaret A. 
Published: March 2014

AbstractAntimicrobial peptides and proteins represent an important class of plant defensive compounds against pathogens and provide a rich source of lead compounds in the field of drug discovery. We describe the effective preparation of the cysteine‐rich snakin‐1 and ‐2 antimicrobial peptides by using a combination of solid‐phase synthesis and native chemical ligation. A subsequent cysteine/cystine mediated oxidative folding to form the six internal disulfide bonds concurrently gave the folded proteins in 40–50 % yield. By comparative evaluation of mass spectrometry, HPLC, biological data and trypsin digest mapping of folded synthetic snakin‐2 compared to natural snakin‐2, we demonstrated that synthetic snakin‐2 possesses full antifungal activity and displayed similar chromatographic behaviour to natural snakin‐2. Trypsin digest analysis allowed tentative assignment of three of the purported six disulfide bonds.
Switching Regioselectivity of β‐Ketothioamides by Means of Iodine Catalysis: Synthesis of Thiazolylidenes and 1,4‐Dithiines
Authors: Wen Li‐Rong , Men Lian‐Bin , He Tao , Ji Guo‐Jing , Li Ming 
Published: March 2014

AbstractAn efficient I2‐catalyzed synthesis of thiazolylidenes and 1,4‐dithiines from β‐ketothioamides (KTAs) has been developed by only controlling the amount of I2 that triggers different cascade reaction sequences by means of [3+2] or [3+3] cyclocondensation in a one‐step process. A possible mechanistic proposal for these transformations is presented.
Metal–Organic Frameworks: From Molecules/Metal Ions to Crystals to Superstructures
Authors: Carné‐Sánchez Arnau , Imaz Inhar , Stylianou Kyriakos C. , Maspoch Daniel 
Published: March 2014

AbstractMetal–organic frameworks (MOFs) are among the most attractive porous materials known today, exhibiting very high surface areas, tuneable pore sizes and shapes, adjustable surface functionality, and flexible structures. Advances in the formation of MOF crystals, and in their subsequent assembly into more complex and/or composite superstructures, should expand the scope of these materials in many applications (e.g., drug delivery, chemical sensors, selective reactors and removal devices, etc.) and facilitate their integration onto surfaces and into devices. This Concept article aims to showcase recently developed synthetic strategies to control the one‐, two‐ and three‐dimensional (1‐, 2‐ and 3D) organisation of MOF crystals.
Cerium(III/IV) Formamidinate Chemistry, and a Stable Cerium(IV) Diolate
Authors: Werner Daniel , Deacon Glen B. , Junk Peter C. , Anwander Reiner 
Published: March 2014

AbstractFour new cerium(III) formamidinate complexes comprising [Ce(p‐TolForm)3], [Ce(DFForm)3(thf)2], [Ce(DFForm)3], and [Ce(EtForm)3] were synthesized by protonolysis reactions using [Ce{N(SiMe3)2}3] and formamidines of varying functionality, namely N,N′‐bis(4‐methylphenyl)formamidine (p‐TolFormH), N,N′‐bis(2,6‐difluorophenyl)formamidine (DFFormH), and the sterically more demanding N,N′‐bis(2,6‐diethylphenyl)formamidine (EtFormH). The bimetallic cerium lithium complex [LiCe(DFForm)4] was synthesized by treating a mixture of [Ce{N(SiHMe2)2}3(thf)2] and [Li{N(SiHMe2)2}] with four equivalents of DFFormH in toluene. Oxidation of the trivalent cerium(III) formamidinate complexes by trityl chloride (Ph3CCl) caused dramatic color changes, although the cerium(IV) species appeared transient and reformed cerium(III) complexes and N′‐trityl‐N,N′‐diarylformamidines shortly after oxidation. The first structurally characterized homoleptic cerium(IV) formamidinate complex [Ce(p‐TolForm)4] was obtained through a protonolysis reaction between [Ce{N(SiHMe2)2}4] and four equivalents of p‐TolFormH. [Ce{N(SiHMe2)2}4] was also treated with DFFormH and EtFormH, but the resulting cerium(IV) complexes decomposed before isolation was possible. The new cerium(IV) silylamide complex [Ce{N(SiMe3)2}3(bda)0.5]2 (bda=1,4‐benzenediolato) was synthesized by treatment of [Ce{N(SiMe3)2}3] with half an equivalent of 1,4‐benzoquinone, and showed remarkable resistance towards protonolysis or reduction.
Metal Ion, Light, and Redox Responsive Interaction of Vesicles by a Supramolecular Switch
Authors: Samanta Avik , Ravoo Bart Jan 
Published: March 2014

AbstractChemical, photochemical and electrical stimuli are versatile possibilities to exert external control on self‐assembled materials. Here, a trifunctional molecule that switches between an “adhesive” and a “non‐adhesive” state in response to metal ions, or light, or oxidation is presented. To this end, an azobenzene–ferrocene conjugate with a flexible N,N′‐bis(3‐aminopropyl)ethylenediamine spacer was designed as a multistimuli‐responsive guest molecule that can form inclusion complexes with β‐cyclodextrin. In the absence of any stimulus the guest molecule induces reversible aggregation of host vesicles composed of amphiphilic β‐cyclodextrin due to the formation of intervesicular inclusion complexes. In this case, the guest molecule operates as a noncovalent cross‐linker for the host vesicles. In response to any of three external stimuli (metal ions, UV irradiation, or oxidation), the conformation of the guest molecule changes and its affinity for the host vesicles is strongly reduced, which results in the dissociation of intervesicular complexes. Upon elimination or reversal of the stimuli (sequestration of metal ion, visible irradiation, or reduction) the affinity of the guest molecules for the host vesicles is restored. The reversible cross‐linking and aggregation of the cyclodextrin vesicles in dilute aqueous solution was confirmed by isothermal titration calorimetry (ITC), optical density measurements at 600 nm (OD600), dynamic light scattering (DLS), ζ‐potential measurements and cyclic voltammetry (CV). To the best of our knowledge, a dynamic supramolecular system based on a molecular switch that responds orthogonally to three different stimuli is unprecedented.
Redox Behaviour of Cymantrene Fischer Carbene Complexes in Designing Organometallic Multi‐tags
Authors: Bezuidenhout Daniela I. , van der Westhuizen Belinda , Swarts Pieter J. , Chatturgoon Teshica , Munro Orde Q. , Fernández Israel , Swarts Jannie C. 
Published: March 2014

AbstractA series of Group 7 Fischer carbene complexes, [Cp(CO)2MnI=C(OEt)Ar] (Cp=cyclopentadienyl, Ar=Th=thienyl (1 a), Ar=Fu=furyl (2 a), Ar=Fc=ferrocenyl (3 a)) and biscarbene complexes, [Cp(CO)2MnC(OEt)Ar′(OEt)CMn(CO)2Cp] (Ar′=Th′=2,5‐thienylene (1 b), Ar′=Fu′=2,5‐furylene (2 b), Ar′=Fc′=1,1′‐ferrocendiyl (3 b)) was synthesized and characterized. Chemical oxidation of [Cp(CO)2MnC(OEt)Fc] (3 a) and isolation of the oxidised species[3 a][PF6]possessing a MnIIcentre proved possible below −30 °C in dichloromethane solution. The ESR spectrum of the transiently stable radical cation,[3 a][PF6], confirmed the presence of a low‐spin MnIIcentre characterized by a rhombicgtensor (gx=1.975,gy=2.007 andgz=2.130) in frozen dichloromethane at 77 K with55 Mn hyperfine coupling constantsA1,A2andA3of 115, 33 and 43 G, respectively. Electrochemical studies demonstrated the influence of the Ar substituent on the oxidation potential. All complexes showed that the redox potentials of carbene double bond reduction and MnIoxidation were dependent on the type of Ar group, but only3 bshowed resolved oxidations for the two MnIcentres. Surprisingly, MnIoxidation occurs at lower potentials than ferrocenyl oxidation. Density functional theory (DFT) calculations were carried out to delineate the nature of the species involved in the oxidation and reduction processes and clearly confirm that oxidation of MnIis favoured over that of ferrocene.
Rational Design of Ni Nanoparticles on N‐Rich Ultrathin Carbon Nanosheets for High‐Performance Supercapacitor Materials: Embedded‐ Versus Anchored‐Type Dispersion
Authors: Yang Mei , Zhong Yiren , Su Liwei , Wei Jinping , Zhou Zhen 
Published: March 2014

AbstractHighly dispersed Ni nanoparticles (NPs) and abundant functional N‐species were integrated into ultrathin carbon nanosheets by using a facile and economical sol–gel route. Embedded‐ and anchored‐type configurations were achieved for the dispersion of Ni NPs in/on N‐rich carbon nanosheets. The anchored‐type composite exhibited outstanding pseudocapacitance of 2200 F g−1 at 5 A g−1 with unusual rate capability and extraordinary cyclic stability over 20 000 cycles with little capacitance decay. Aqueous asymmetric supercapacitors fabricated with this composite cathode demonstrated a high energy density of 51.3 Wh kg−1 at a relatively large power density of 421.6 W kg−1, along with outstanding cyclic stability. This approach opens an attractive direction for enhancing the electrochemical performances of metal‐based supercapacitors and can be generalized to design high‐performance energy‐storage devices.
Magnesium Complexes as Highly Effective Catalysts for Conjugate Cyanation of α,β‐Unsaturated Amides and Ketones
Authors: Zhang Jinlong , Liu Xihong , Wang Rui 
Published: March 2014

AbstractAsymmetric cyanation of trimethylsilyl cyanide (TMSCN) with α,β‐unsaturated amides and ketones, respectively, catalyzed by bifunctional mononuclear 1,1′‐bi‐2‐naphthol (BINOL)–Mg and binuclear bis(prophenol)–Mg catalysts was realized. A series of synthetically important 1,4‐cyano products were obtained with good to high enantioselectivities (up to 97 % ee).
Templating the Self‐Assembly of Pristine Carbon Nanostructures in Water
Authors: Mba Miriam , Jiménez Ana I. , Moretto Alessandro 
Published: March 2014

AbstractThe low solubility of carbon nanostructures (CNs) in water and the need of ordered architectures at the nanoscale level are two major challenges for materials chemistry. Here we report that a novel amino acid based low‐molecular‐weight gelator (LMWG) can be used to effectively disperse pristine CNs in water and to drive their ordered self‐assembly into supramolecular hydrogels. A non‐covalent mechanochemical approach has been used, so the π‐extended system of the CNs remains intact. Optical spectroscopy and electron microscopy confirmed the effective dispersion of the CNs in water. Electron microscopy of the hydrogels showed the formation of an ordered, LMWG‐assisted, self‐assembled architecture. Moreover, the very same strategy allows the solubilization and self‐assembly in water of a variety of hydrophobic molecules.
Capsules with Highly Active Pores and Interiors: Versatile Platforms at the Nanoscale
Authors: Müller Achim , Gouzerh Pierre 
Published: March 2014

AbstractSpherical porous capsules offer new exciting approaches in chemistry, materials sciences, and in context of physical and biological phenomena. The underlying concepts are reported with particular emphasis on metal oxide based capsules of the {M132} Keplerate type which display—due to their exceptional structural features and easy variation/derivatization as well as exchange of building units—an unmatched range of properties and offer unique opportunities for investigating a variety of basic aspects of nanoscience, including the discovery of some new phenomena, especially those related to hydrophobicity issues that are of significance for everyday life. This relies in particular on the existence of a large number of flexible crown ether type pores/channels and the possibility of changing the interior from completely hydrophilic to completely hydrophobic due to the presence of numerous easily exchangeable internal ligands/functionalities; the capsules can even be constructed so that they enclose a large number of highly active Lewis and Brønsted acid sites. The manifold of possible applications/uses are outlined as subtitles with reference to results as well as possible future studies. There are, among many others, options to control passing cations under different internal frames allowing also their separations, to conduct studies about hydrophobic recognitions and clustering of biological interest in water, controlled internal ion transport, nanoscale dewetting, and to carry out basic as well as new types of reactions under confined conditions.
Halometallate Complexes of Germanium(II) and (IV): Probing the Role of Cation, Oxidation State and Halide on the Structural and Electrochemical Properties
Authors: Bartlett Philip N. , Cummings Charles Y. , Levason William , Pugh David , Reid Gillian 
Published: March 2014

AbstractThe GeIV chlorometallate complexes, [EMIM]2[GeCl6], [EDMIM]2[GeCl6] and [PYRR]2[GeCl6] (EMIM=1‐ethyl‐3‐methylimidazolium; EDMIM=2,3‐dimethyl‐1‐ethylimidazolium; PYRR=N‐butyl‐N‐methylpyrrolidinium) have been synthesised and fully characterised; the first two also by single‐crystal X‐ray diffraction. The imidazolium chlorometallates exhibited significant CH⋅⋅⋅Cl hydrogen bonds, resulting in extended supramolecular assemblies in the solid state. Solution 1H NMR data also showed cation–anion association. The synthesis and characterisation of GeII halometallate salts [EMIM][GeX3] (X=Cl, Br, I) and [PYRR][GeCl3], including single‐crystal X‐ray analyses for the homologous series of imidazolium salts, are reported. In these complexes, the intermolecular interactions are much weaker in the solid state and they appear not to be significantly associated in solution. Cyclic‐voltammetry experiments on the GeIV species in CH2Cl2 solution showed two distinct, irreversible reduction waves attributed to GeIV–GeII and GeII–Ge0, whereas the GeII species exhibited one irreversible reduction wave. The potential for the GeII–Ge0 reduction was unaffected by changing the cation, although altering the oxidation state of the precursor from GeIV to GeII does have an effect; for a given cation, reduction from the [GeCl3]− salts occurred at a less cathodic potential. The nature of the halide co‐ligand also has a marked influence on the reduction potential for the GeII–Ge0 couple, such that the reduction potentials for the [GeX3]− salts become significantly less cathodic when the halide (X) is changed Cl→Br→I.
Stereostructural Implication by the Differential Bond Polarizability: ROA Intensity Study of Chiral S 2‐Amino 1‐Propanol
Authors: Wu Guozhen , Wang Peijie 
Published: March 2014

ABSTRACTThe bond polarizability and differential bond polarizability are introduced to interpret the Raman and Raman optical activity (ROA) intensities, calculated by the ab initio method. Chiral S 2‐amino 1‐propanol is taken as a model molecule. Through these bond polarizabilities, we observe that symmetric and antisymmetric coordinates are, respectively, more significant in Raman and ROA. It is noted that in S 2‐amino 1‐propanol those bonds lying on a common plane share the same differential bond polarizability sign while that of the asymmetric C‐H bond which protrudes out of the plane possesses the opposite sign. We conclude that ROA can offer more stereostructural implications than Raman and that the differential bond polarizability is potentially the appropriate parameter in interpreting the 3D configuration of a molecule. Chirality 26:255–259, 2014. © 2014 Wiley Periodicals, Inc.
Electrically Assisted Liquid‐Phase Microextraction Combined With Capillary Electrophoresis for Quantification of Propranolol Enantiomers in Human Body Fluids
Authors: Tabani Hadi , Fakhari Ali Reza , Shahsavani Abolfath , Gharari Alibabaou Hossein 
Published: March 2014

ABSTRACTIn this study, electromembrane extraction (EME) combined with cyclodextrin (CD)‐modified capillary electrophoresis (CE) was applied for the extraction, separation, and quantification of propranolol (PRO) enantiomers from biological samples. The PRO enantiomers were extracted from aqueous donor solutions, through a supported liquid membrane (SLM) consisting of 2‐nitrophenyl octyl ether (NPOE) impregnated on the wall of the hollow fiber, and into a 20‐μL acidic aqueous acceptor solution into the lumen of hollow fiber. Important parameters affecting EME efficiency such as extraction voltage, extraction time, pH of the donor and acceptor solutions were optimized using a Box‐Behnken design (BBD). Then, under these optimized conditions, the acceptor solution was analyzed using an optimized CD‐modified CE. Several types of CD were evaluated and best results were obtained using a fused‐silica capillary with ammonium acetate (80 mM, pH 2.5) containing 8 mM hydroxypropyl‐β‐CD as a chiral selector, applied voltage of 18 kV, and temperature of 20°C. The relative recoveries were obtained in the range of 78–95%. Finally, the performance of the present method was evaluated for the extraction and determination of PRO enantiomers in real biological samples. Chirality 26:260–267, 2014. © 2014 Wiley Periodicals, Inc.
Perspectives on barriers and facilitators to minority recruitment for clinical trials among cancer center leaders, investigators, research staff, and referring clinicians: Enhancing minority participation in clinical trials (EMPaCT)
Authors: Durant Raegan W. , Wenzel Jennifer A. , Scarinci Isabel C. , Paterniti Debora A. , Fouad Mona N. , Hurd Thelma C. , Martin Michelle Y. 
Published: March 2014

BACKGROUNDThe study of disparities in minority recruitment to cancer clinical trials has focused primarily on inquiries among minority populations. Yet very little is known about the perceptions of individuals actively involved in minority recruitment to clinical trials within cancer centers. Therefore, the authors assessed the perspectives of cancer center clinical and research personnel on barriers and facilitators to minority recruitment.METHODSIn total, 91 qualitative interviews were conducted at 5 US cancer centers among 4 stakeholder groups: cancer center leaders, principal investigators, research staff, and referring clinicians. All interviews were recorded and transcribed. Qualitative analyses of response data was focused on identifying prominent themes related to barriers and facilitators to minority recruitment.RESULTSThe perspectives of the 4 stakeholder groups were largely overlapping with some variations based on their unique roles in minority recruitment. Four prominent themes were identified: 1) racial and ethnic minorities are influenced by varying degrees of skepticism related to trial participation, 2) potential minority participants often face multilevel barriers that preclude them from being offered an opportunity to participate in a clinical trial, 3) facilitators at both the institutional and participant level potentially encourage minority recruitment, and 4) variation between internal and external trial referral procedures may limit clinical trial opportunities for racial and ethnic minorities.CONCLUSIONSMultilevel approaches are needed to address barriers and optimize facilitators within cancer centers to enhance minority recruitment for cancer clinical trials. Cancer 2014;120(7 suppl):1097–105. © 2014 American Cancer Society.