bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contributions to the Structural Chemistry of 2‐Amino Alcoholate Derivatives of Titanium and Zirconium Alkoxides and Their Partial Hydrolysis Products
Authors: Fric Helmut , Puchberger Michael , Schubert Ulrich 
Published: February 2008

AbstractThe structures of Ti2(OiPr)6(OCHMeCH2NH2)2 and Ti2(OiPr)6(OCH2CHMeNH2)2, obtained by reaction of Ti(OiPr)4 with the corresponding amino alcohols, were investigated to elucidate the structural influence of the organic substituents at the amino alcohol. A methyl group at the OH‐substituted carbon atom results in a larger distortion of the structure than a methyl group at the NH2‐substituted carbon. The disubstituted compound Ti2(OiPr)4(OCH2CH2NH2)4 was formed, when NaTi(OiPr)5 was reacted the amino ethanol. While one OCH2CH2NH2 ligand is chelating, the oxygen atom of the second bridges the titanium atoms, and the NH2 group is dangling. The structures of the partial hydrolysis products Ti4O4(OiPr)4(OCHPhCHMeNHMe)4 and Ti8O6(OEt)12(OCH2CH2NH2)8 were also investigated. The former contains an incomplete double‐cube Ti4O4 cluster core, the latter is made of two Ti4O3(OEt)6(OCH2CH2NH2)4 sub‐units, with a nearly planar Ti4(μ2‐O)2(μ3‐O)(μ2‐OEt)2 ring system, connected by two OEt bridges. Zr(OCH2CH2NH2)4 is a mononuclear compound with four chelating amino alcoholate ligands. The structure of Zr6(OBu)18(OCH2CH2NH2)6 is assembled from two Zr2(OBu)5(OCH2CH2NH2)3 and two Zr(OBu)4 sub‐units, which are associated by alkoxo bridges. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Visible‐Light Excitation of Infrared Lanthanide Luminescence via Intra‐Ligand Charge‐Transfer State in 1,3‐Diketonates Containing Push‐Pull Chromophores
Authors: Shavaleev Nail M. , Scopelliti Rosario , Gumy Frédéric , Bünzli Jean‐Claude G. 
Published: February 2008

AbstractA new 1,3‐diketonato ligand containing both an electron‐donor [4‐(dimethylamino)benzene] and an electron‐acceptor (4‐nitrobenzene) group and its lanthanide complexes have been prepared. They display an intense intra‐ligand charge‐transfer absorption transition in the visible region of the spectrum at 400–550 nm which was utilized to achieve visible‐light excitation of metal‐centred infrared luminescence of NdIII, ErIII and YbIII ions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Reduction of Ketones with Hydrocarbon‐Soluble Calcium Hydride: Stoichiometric Reactions and Catalytic Hydrosilylation
Authors: Spielmann Jan , Harder Sjoerd 
Published: February 2008

AbstractReactions of the dimeric calcium hydride complex[(DIPP‐nacnac)CaH·thf]2 {1; DIPP‐nacnac = CH[(CMe)(2,6‐iPr2C6H3N)]2} with the α‐hydrogen containing ketones acetophenone, acetone, dibenzylketone and 2‐adamantone are smooth. In most cases not only addition but also substantial enolization is observed as a side reaction and in some cases also aldol condensation was found. Despite this unselectivity, the addition products could be isolated crystalline pure. Crystal structures of [(DIPP‐nacnac)CaOCH(Me)Ph]2 (3), [(DIPP‐nacnac)CaOCH(CH2Ph)2]2 (6) and [(DIPP‐nacnac)Ca(2‐adamantoxide)]2 (7) have been determined. The calcium hydride complex 1 is an effective catalyst in the hydrosilylation of ketones. Independent from the silane/ketone ratio, a strong preference for formation of bis‐alkoxy silanes [PhSiH(OR)2] is observed. In most cases no enoxy groups have been found in the product. This indicates that the mechanism does not involve addition of the calcium hydride to the ketone functionality. A concerted addition of silane to ketone through a six‐coordinate hypervalent silicon intermediate is proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
A Ruthenium‐Catalyzed Approach to the Friedländer Quinoline Synthesis
Authors: Vander Mierde Hans , Van Der Voort Pascal , De Vos Dirk , Verpoort Francis 
Published: February 2008

AbstractIn a modification of the Friedländer reaction, 2‐aminobenzyl alcohol is oxidatively cyclized with a variety of ketones to yield substituted quinolines. Of all the ruthenium catalysts that were tested for this reaction, the second‐generation Grubbs' catalyst gives the highest quinoline yield, in combination with KOtBu as a base. The presence of a hydrogen acceptor is required to regenerate the catalyst. Also the reaction mechanism is discussed, and the results show that there are possibly two different pathways towards quinolines.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Synthesis of Annulenes via Multiple Wittig Reactions; In‐Situ Dimerization of 1,2;5,6‐Dibenzocyclooctatetraene
Authors: Bornhöft Jan , Siegwarth Jan , Näther Christian , Herges Rainer 
Published: February 2008

AbstractA simple synthetic route to tetrabenzo[16]‐ and hexabenzo[24]annulene systems using one‐pot multiple Wittig reactions is presented. We report the characterization of the all‐trans‐isomer of tetrabenzo[16]annulene by NMR spectroscopy and X‐ray diffraction. Several isomers of an unexpected, tetrabenzocyclooctatetraene dimer product are also isolated and identified by NMR‐ and X‐ray diffraction studies.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Electrochemical Characterization of In Situ Functionalized Gold Cysteamine Self‐Assembled Monolayer with 4‐Formylphenylboronic Acid for Detection of Dopamine
Authors: Shervedani Reza Karimi , Bagherzadeh Mojtaba 
Published: February 2008

AbstractFunctionalization of gold cysteamine (AuCA) self‐assembled monolayer with 4‐formylphenylboronic acid (BA) via Schiff's base formation, through in situ method to fabricate Au‐CA‐BA electrode is presented and described. The fabricated electrode was used as a novel sensor for accumulation and determination of dopamine (DA). The accumulation of DA as a diol on the topside of Au‐CA‐BA as a Lewis acid, was performed via esterification (AuCABADA), and followed for determination of DA. Functionalization, characterization, and determination steps were probed by electrochemical methods like cyclic voltammetry and electrochemical impedance spectroscopy. The data will be presented and discussed from which a new sensor for DA is introduced.
Preparation of an Electrode That Immobilizes NAD‐Dependent Alcohol Dehydrogenase by Using a Redox Polymer Containing 1,10‐Phenanthroline‐5,6‐dione
Authors: Motoyama Yusuke , Nakamura Nobuhumi , Ohno Hiroyuki 
Published: February 2008

AbstractA redox polymer (PAHA‐Ru), modified electrode exhibited excellent catalytic activity for the electrochemical oxidation of β‐nicotinamide adenine dinucleotide (NADH). PAHA‐Ru was composed of carboxyl groups and ruthenium complexes containing 1,10‐phenanthroline‐5,6‐dione (phen‐dione). The stability of the PAHA‐Ru film was increased by incorporating poly(diallyldimethylammonium chloride) (PDDA) owing to the formation of a polyelectrolyte complex between the PAHA‐Ru and PDDA. The catalytic efficiency of the oxidation of NADH using the PAHA‐Ru/PDDA‐modified electrode was also greater than that using a PAHA‐Ru‐modified electrode. NAD‐dependent alcohol dehydrogenase (ADH) was entrapped in the PAHA‐Ru/PDDA film on the surface of the glassy carbon electrode. Electrochemical oxidation of ethanol using the ADH‐entrapped electrode was also observed.
Dissolved Cu(II) Speciation in Unpolluted Soil Solutions of a Planosolic Horizon
Authors: Pelfrêne Aurélie , Gassama Nathalie , Grimaud Daniel 
Published: February 2008

AbstractDissolved Cu(II) speciation in unpolluted soil solutions from different horizons was studied using differential pulse anodic stripping voltammetry (DPASV). Three sites were selected according to topography and monitored for three years. Experiments evidence Cu(II) can be bound by DOM (Dissolved Organic Matter) through complexation and/or adsorption reactions. The complexation capacity and the corresponding conditional stability constant were determined for complexation reactions. The adsorbing sites were titrated. A potential binding coefficient was calculated to compare both types of reactions. Results show adsorption is less frequent than complexation but exhibits higher binding coefficient.
Simulation of Redox‐Cycling Phenomena at Interdigitated Array (IDA) Electrodes: Amplification and Selectivity
Authors: Odijk M. , Olthuis W. , Dam V. A. T. , van den Berg A. 
Published: February 2008

AbstractWe present Finite Element Method (FEM) simulations of interdigitated array (IDA) electrode geometries to study and verify redox selectivity and redox cycling amplification factor. The simulations provide an adequate explanation of an earlier found, but poorly understood, high amplification factor (65×) in a 1 μm‐spaced IDA microdevice. Moreover, using the FEM calculations we present selectivity measurements with IDA electrodes in a mixture of two redox species, as for example dopamine and ferricyanide. We show that it is possible to electrochemically detect dopamine in presence of the stronger reductor ferricyanide, which is impossible with direct amperometric detection, with the use of IDA electrodes with proper polarization potential of the collector electrode. Using our simulations, we show that a theoretical selectivity of dopamine over ferricyanide of 11 can be achieved.
Renewable Copper and Silver Amalgam Film Electrodes of Prolonged Application for the Determination of Elemental Sulfur Using Stripping Voltammetry
Authors: Piech Robert , Baś Bogusław , Niewiara Ewa , Kubiak Władysław W. 
Published: February 2008

AbstractNew, renewable copper (Hg(Cu)FE) and silver (Hg(Ag)FE) based amalgam film electrodes applied for the determination of elemental sulfur using differential pulse cathodic stripping voltammetry are presented. With surface areas adjustable from 1 to 12 mm2, both electrodes are characterized by very good surface reproducibility (≤2%) and long‐term stability (a few thousand measurement cycles). The mechanical refreshing of the amalgam film takes about 1–2 seconds. The effects of various factors such as instrumental parameters and the supporting electrolyte composition were optimized. Interferences from sulfides are easily removed by the addition of acid, and bubbling with argon, for Hg(Ag)FE. In the case of Hg(Cu)FE, sulfides did not interfere. The calibration graph is linear within the studied range from 16 ng L−1 to 4.8 μg L−1 for Hg(Cu)FE, and up to 6.4 μg L−1 for Hg(Ag)FE (tacc=15 s). The correlation coefficients for the two electrodes were at least 0.997. The detection limits for a low concentration of S(0) and tacc=60 s are as low as 14 ng L−1 for Hg(Cu)FE and 4 ng L−1 for Hg(Ag)FE. The proposed method was successfully applied and validated by studying the recovery of S(0) from spiked river water.
Effect of pH on the Enantiospecificity of Homocysteine Monolayer on Au(111) for the Redox Reaction of 3,4‐Dihydroxyphenylalanine
Authors: Matsunaga Mariko , Nagasaka Makoto , Nakanishi Takuya , Sawaguchi Takahiro , Osaka Tetsuya 
Published: February 2008

AbstractThe effect of pH on the enantiospecificity of Au (111) electrode modified with L‐homocysteine was evaluated for the electrochemical redox reaction of 3,4‐dihydroxyphenylalanine (DOPA). Cyclic voltammetric peaks clearly exhibited enantiospecificity at pH 0.6 and 2, whereas no enantiospecificity was observed at pH 3, 4, and 5.5. Scanning tunneling microscopy confirmed the highly ordered (2√3×3√3)R30° structure of L‐homocysteine at pH 0.6, at which L‐homocysteine molecules form a dimer through the hydrogen‐bond between carboxy groups (COOH), while a disordered structure was observed at pH 5.5. These results suggest that the dimer formed in the acidic solutions at pH below 3 plays an important role in providing the enantiospecificity to the Au(111) surface.
Carboxyphenyl Covalent Immobilization of Heme Proteins and its Favorable Biocompatible Electrochemical and Electrocatalytic Characteristics
Authors: Liu Meichuan , Qi Yuan , Zhao Guohua 
Published: February 2008

AbstractA novel carboxyphenyl covalent immobilization technique has been successfully developed to realize the effective attachment of two typical heme proteins, hemoglobin (Hb) and cytochrome c (Cyt‐c), onto underlying glassy carbon electrode (GCE). Primarily, the GCE surface is functionalized with aromatic 4‐carboxyphenyl (4‐CP) group by the electrochemical reduction of diazonium cations, producing covalently linked carboxyl‐terminated active GCE surface to work as a ‘bridge’. Then, Hb and Cyt‐c are readily attached to GCE through the ‘bridge’ by functional covalently combination between NH2 terminal groups of proteins and COOH terminal groups of 4‐CP, obtaining Hb/4‐CP/GCE and Cyt‐c/4‐CP/GCE. On both electrodes, well‐defined peaks attributing to the FeIII/FeII couple of heme group of Hb and Cyt‐c are clearly observed with the electron transfer rate constant (ks) evaluated to be 2.48±0.05 s−1 and 2.73±0.05 s−1, respectively. It is attractive that the formal potential (E°') of the immobilized Hb and Cyt‐c are estimated to be 50 and 100 mV (vs. SCE), respectively, which are closer to the standard redox potential of native Hb and Cyt‐c in solution, owing to the good biocompatibility of 4‐CP groups. The electrodes also exhibit fast response, high sensitivity and well stability for the amperometric detection of H2O2 at a fairly mild potential of 0 V without any mediators, obtaining rather small apparent Michaelis‐Menten constant (KMapp) values of 113 μM for Hb/4‐CP/GCE and 101 μM for Cyt‐c/4‐CP/GCE. All the experimental results indicated that the covalent graft 4‐carboxyphenyl group plays an important role in constructing a “biocompatible bridge” to help the direct electron transfer of Hb and Cyt‐c with favorable biocompatibility and good bio‐ electrocatalytic affinity in virtue of the substituted aryl group only consisting of C, H and O elements, which is similar with the constitutes of organics. It makes the system of functionalized covalent immobilization of proteins onto carbon electrode a promising platform for fabricating the third‐generation biosensors. A new approach for realizing direct electrochemistry of proteins, as well as design of novel bioelectronic devices has been accordingly provided.
Direct Heterogeneous Electron Transfer Reactions of Bacillus halodurans Bacterial Blue Multicopper Oxidase
Authors: Shleev Sergey , Wang Yan , Gorbacheva Marina , Christenson Andreas , Haltrich Dietmar , Ludwig Roland , Ruzgas Tautgirdas , Gorton Lo 
Published: February 2008

AbstractDirect electron transfer reactions of Bacillus halodurans bacterial multicopper oxidase on bare spectrographic graphite, as well as bare and thiol‐modified gold electrodes were studied using cyclic voltammetry, potentiometry, amperometry, and spectroelectrochemistry. The redox potential of the T1 site of the enzyme was measured using mediatorless redox titration and found to be 325 mV±10 mV vs. NHE. From measurements with a mercaptopropionic acid‐modified gold electrode under aerobic conditions a midpoint potential of 360 mV vs. NHE for the T2/T3 copper cluster is deduced. Differing from most other characterized laccases of fungal and plant origins this bacterial enzyme exhibits bioelectrocatalytic activity at neutral pH and tolerates high chloride concentrations (200 mM), conditions that usually strongly inhibit catalysis. Moreover, it has the very high affinity towards molecular oxygen both in solution and in the adsorbed state (KM≤50 μM).
Investigation of Airbrushing for Fabricating Microelectrodes in Microfluidic Devices
Authors: Walker Corey E. , Xia Zheng , Foster Zachary S. , Lutz Brent J. , Fan Z. Hugh 
Published: February 2008

AbstractWe report fabrication of microelectrodes by airbrushing, a technique primarily used for commercial arts. Similar to screen‐printing, airbrushing enables conductive inks to be patterned onto a thin film. The film with ink electrodes is then laminated with a plastic substrate with microchannels to form a microfluidic device. The device is designed to implement enzyme‐catalyzed electrochemical detection for sensing hydrogen. We found that airbrushed electrodes perform in a similar fashion with screen‐printed electrodes. The cyclic voltammetric peak separation for ferrocyanide is 0.34 V, suggesting a nonreversible redox behavior as observed for the screen‐printed ink electrodes. A linear calibration curve is obtained for 2 to 20 mM ferrocyanide in a flow using chronoamperometry, which is the method we previously exploited for demonstrating enzyme‐catalyzed electrochemical detection in a large flow cell. The process parameters of airbrushing, including ink concentration, have been characterized. The benefits of fabricating electrodes by airbrushing include a simpler process, lower cost, and requiring less skill. This technique is especially useful in situations where a commercial screen‐printing machine is inaccessible.
Electrocatalytic Determination of Sulfite at Immobilized Microdroplet Liquid|Liquid Interfaces: The EIC′ Mechanism
Authors: Katif Najoua , MacDonald Stuart M. , Kelly Andrew M. , Galbraith Ewan , James Tony D. , Lubben Anneke T. , Opallo Marcin , Marken Frank 
Published: February 2008

AbstractLiquid|liquid interfaces provide a natural boundary and a reactive interface where an organic phase is in contact with an aqueous analyte. The selectivity of ion transfer processes at liquid|liquid interfaces can help to provide sensitivity, introduce reactive reagents, or allow analyte accumulation at the electrode surface. In this study, microdroplet deposits of the organic liquid 4‐(3‐phenylpropyl)‐pyridine (PPP) with the ferrocenylmethyl‐dodecyldimethylammonium+ (FDA+) redox system are deposited onto a basal plane pyrolytic graphite electrode and employed to transfer anions from the aqueous into the organic phase. A clear trend of more hydrophobic anions transferring more readily (at more negative potentials) is observed and an ESI‐mass spectrometry method is developed to confirm the transfer. Subsequently, the electrocatalytic oxidation of sulfite, SO32−, within the organic phase and in the presence of different electrolyte anions is investigated. Competition between sulfite transfer and inert anion transfer occurs. The electrocatalytic sulfite oxidation is suppressed in the presence of PF6− and occurs most readily in the presence of the hydrophilic nitrate anion. The resulting process can be classified as an electrocatalytic EIC′‐process (E: electron transfer; I: ion transfer; C: chemical reaction step). The effectiveness of the electrocatalytic process is limited by i) competition during anion transfer and ii) the liquid|liquid interface acting as a diffusion barrier. The analytical sensitivity of the method is limited to ca. 100 μM SO32− (or ca. 8 ppm) and potential approaches for improvement of this limit are discussed.
The zeta potential of surface‐functionalized metallic nanorod particles in aqueous solution
Authors: Dougherty George M. , Rose Klint A. , Tok Jeffrey B.‐H. , Pannu Satinderpall S. , Chuang Frank Y. S. , Sha Michael Y. , Chakarova Gabriela , Penn Sharron G. 
Published: February 2008

AbstractMetallic nanoparticles suspended in aqueous solutions and functionalized with chemical and biological surface coatings are important elements in basic and applied nanoscience research. Many applications require an understanding of the electrokinetic or colloidal properties of such particles. We describe the results of experiments to measure the zeta potential of metallic nanorod particles in aqueous saline solutions, including the effects of pH, ionic strength, metallic composition, and surface functionalization state. Particle substrates tested include gold, silver, and palladium monometallic particles as well as gold/silver bimetallic particles. Surface functionalization conditions included 11‐mercaptoundecanoic acid (MUA), mercaptoethanol (ME), and mercaptoethanesulfonic acid (MESA) self‐assembled monolayers (SAMs), as well as MUA layers subsequently derivatized with proteins. For comparison, we present zeta potential data for typical charge‐stabilized polystyrene particles. We compare experimental zeta potential data with theoretically predicted values for SAM‐coated and bimetallic particles. The results of these studies are useful in predicting and controlling the aggregation, adhesion, and transport of functionalized metallic nanoparticles within microfluidic devices and other systems.
NURBS‐enhanced finite element method for Euler equations
Authors: Sevilla R. , Fernández‐Méndez S. , Huerta A. 
Published: February 2008

AbstractIn this work, the NURBS‐enhanced finite element method (NEFEM) is combined with a discontinuous Galerkin (DG) formulation for the numerical solution of Euler equations of gas dynamics. With NEFEM, numerical fluxes along curved boundaries are computed much more accurately due to the exact geometric representation of the computational domain. The proper implementation of the wall boundary condition and the exact geometry provide accurate results even with a linear approximation of the solution. A detailed comparison of NEFEM in front of isoparametric finite elements is presented, demonstrating the superiority of NEFEM approach for both linear and higher‐order computations. Copyright © 2008 John Wiley & Sons, Ltd.
Partially segregated neural networks for spatial and contextual memory in virtual navigation
Authors: Rauchs Géraldine , Orban Pierre , Balteau Evelyne , Schmidt Christina , Degueldre Christian , Luxen André , Maquet Pierre , Peigneux Philippe 
Published: February 2008

AbstractFinding our way in a previously learned, ecologically valid environment concurrently involves spatial and contextual cognitive operations. The former process accesses a cognitive map representing the spatial interactions between all paths in the environment. The latter accesses stored associations between landmark objects and their milieu. Here, we aimed at dissociating their neural basis in the context of memory‐based virtual navigation. To do so, subjects freely explored a virtual town for 1 h, then were scanned using fMRI while retrieving their way between two locations, under four navigation conditions designed to probe separately or jointly the spatial and contextual memory components. Besides prominent commonalities found in a large hippocampo‐neocortical network classically involved in topographical navigation, results yield evidence for a partial dissociation between the brain areas supporting spatial and contextual components of memory‐based navigation. Performance‐related analyses indicate that hippocampal activity mostly supports the spatial component, whereas parahippocampal activity primarily supports the contextual component. Additionally, the recruitment of contextual memory during navigation was associated with higher frontal, posterior parietal and lateral temporal activity. These results provide evidence for a partial segregation of the neural substrates of two crucial memory components in human navigation, whose combined involvement eventually leads to efficient navigation behavior within a learned environment. © 2008 Wiley‐Liss, Inc.