bluuebunny/crossref_metadata_2025 huggingface dataset:
Mono‐ and Dinuclear CuII and ZnII Complexes of Cyclen‐Based Bis(macrocycles) Containing Two Aminoalkyl Pendant Arms of Different Lengths
Authors: Anda Carmen , Bencini Andrea , Berni Emanuela , Ciattini Samuele , Chuburu Françoise , Danesi Andrea , Giorgi Claudia , Handel Henri , Le Baccon Michel , Paoletti Piero , Tripier Raphaël , Turcry Véronique , Valtancoli Barbara
Published: June 2005

The basicity and coordination properties towards CuII and ZnII of the bis(macrocycles) L1, L2 and L3 have been investigated by means of potentiometric, 1H NMR and UV/Vis spectroscopic titrations in aqueous solutions. The synthesis of L1 and L3 is also described. The three ligands are composed of two [12]aneN4 units separated by a p‐phenylene spacer and differ in the length of the aminoalkyl pendant arms linked to each macrocyclic unit. L1–L3 form mono‐ and dinuclear complexes in aqueous solutions; in the dinuclear species each metal ion is coordinated by one of the two identical [12]aneN4 ligand moieties, as shown by the crystal structures of the complexes [Cu2L1]Cl4·8H2O, [Zn2L2](ClO4)4 and [Zn2L3](ClO4)4·H2O. In all structures the metal ion is pentacoordinate, and is bound to the four nitrogen donors of the cyclic unit and to the amine group of the side arm. The stability of both the [ML]2+ and [M2L]4+ complexes in aqueous solution decreases in the order L1 > L2 > L3. At the same time, both the [Cu2L]4+ and [Zn2L]4+ complexes show a different ability in proton binding among the three ligands, with the [M2L1]4+ complexes displaying the highest basicity. These results are explained in terms of the decreasing number of nitrogen donors involved in CuII or ZnII binding on passing from L1 to L3; in other words, while in the L1 dinuclear complexes each metal ion is coordinated to the four amine groups of a [12]aneN4 moiety and to the amine group of the side arm, in the L3 ones the metal cations are bound only to the four donor atoms of a cyclic moiety, the aminobutyl group not being coordinated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
A Rearrangement of Azobenzene upon Interaction with an Aluminum(I) Monomer LAl {L = HC[(CMe)(NAr)]2, Ar = 2,6‐iPr2C6H3}
Authors: Zhu Hongping , Chai Jianfang , Fan Hongjun , Roesky Herbert W. , Nehete Umesh N. , Schmidt Hans‐Georg , Noltemeyer Mathias
Published: June 2005

Reaction of LAl (1) or [LAl{η2‐C2(SiMe3)2}] (2) {L = HC[(CMe)(NAr)]2, Ar = 2,6‐iPr2C6H3} with azobenzene affords a five‐membered ring compound [LAl{N(H)‐o‐C6H4N(Ph)}] (3). In the formation of 3 a three‐membered intermediate [LAl(η2‐N2Ph2)] (A) is suggested by a [1 + 2] cycloaddition reaction; A is not stable and further rearranges to 3. DFT calculations on similar compounds with modified L' {L' = HC[(CMe)(NPh)]2} show that the complexation energy of the reaction of L'Al with azobenzene to form [L'Al(η2‐N2Ph2)] is about–39 kcal mol–1, and the best estimate of the energy difference between [L'Al(η2‐N2Ph2)] and [L'Al{N(H)‐o‐C6H4N(Ph)}] is–76 kcal mol–1. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Pyridine‐ and Imidazoledicarboxylates of Zinc: Hydrothermal Synthesis, Structure, and Properties
Authors: Mahata Partha , Natarajan Srinivasan
Published: June 2005

The reaction of hetrocyclic dicarboxylic acids, such as pyridine‐2,5‐dicarboxylic acid and imidazole‐4,5‐dicarboxylic acid, under hydrothermal conditions in the presence of an appropriate zinc salt yields three new zinc coordination polymers 0∞[{Zn2(H2O)4}{C5H3N(COO)2}2] (1), 1∞[{Zn(C12H8N2)}{C5H3N(COO)2}·0.5H2O] (2), and 1∞[{Zn(C12H8N2)}{C3HN2(COO)2}] (3). While 1 forms with a zero‐dimensional molecular rectangular box structure, 2 and 3 have zig‐zag one‐dimensional chain structures. The Zn2+ ions are coordinated by both the carboxylate oxygen atoms and also by the nitrogen atoms of the heterocycles. The 1,10‐phenanthroline molecules in 2 and 3 act as a secondary ligands and occupy the inter‐chain spaces. The moderate hydrogen‐bond interaction energy in 1 and the π···π interactions in 2 and 3 appear to play an important role for the structural stability. The structures of 2 and 3 appear to be related, even though they are formed with different carboxylic acids. All three compounds exhibit photoluminescence at room temperature. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Effects of Anthracene and Pyrene Units on the Interactions of Novel Polypyridylruthenium(II) Mixed‐Ligand Complexes with DNA
Authors: Mariappan Mariappan , Maiya Bhaskar G.
Published: June 2005

2‐(9‐Anthryl)‐1H‐imidazo[4,5‐f][1,10]phenanthroline (aip) and [2‐(1‐pyrenyl)‐1H‐imidazo[4,5‐f][1,10]phenanthroline (pyip) and their complexes [Ru(phen)2(aip)]2+ (1) and [Ru(phen)2(pyip)]2+ (2) (phen = 1,10‐phenanthroline) have been synthesized and characterized by elemental analysis, UV/Vis, IR and 1H NMR spectroscopy, FAB‐MS and cyclic voltammetry methods. Both 1 and 2 are redox‐active and undergo oxidation at 1.43 and 1.47 V (vs. SCE), respectively. Both 1 and 2 show only the 3MLCT emission typical of any polypyridylruthenium(II) complex. These new complexes are seen to be excellent binders of calf‐thymus (CT) DNA, as revealed by the results of absorption, luminescence, viscometric titrations, and thermal denaturation studies. These results also indicate that while ruthenium‐bound aip and pyip intercalate within the base pairs of the duplex, the phen moieties act only as spectator ligands in each case. Steady‐state emission studies carried out in aqueous media with and without DNA reveal that [Ru(phen)2(pyip)]2+ is a better “molecular light switch” for DNA than [Ru(phen)2(aip)]2+. Under an identical set of experimental conditions of light and drug dose, the DNA photocleavage ability of [Ru(phen)2(pyip)]2+ is also higher than that of [Ru(phen)2(aip)]2+. “Inhibitor studies” suggest that the oxygen species are mainly responsible for the DNA photocleavage by these complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthesis of H2V3O8 Single‐Crystal Nanobelts
Authors: Li Gui‐cun , Pang Shu‐ping , Wang Zhao‐bo , Peng Hong‐rui , Zhang Zhi‐kun
Published: June 2005

Orthorhombic H2V3O8 single‐crystal nanobelts with a thickness of less than 30 nm and a length up to several hundreds of micrometers have been synthesized using bulky divanadium pentoxide powders as a precursor. The synthetic process is free of any templates and reducing agents. Divanadium pentoxide undergoes a redox reaction under hydrothermal conditions. The influences of pH, reaction time, and temperature on the morphologies of the resulting products have been investigated. The belt‐like H2V3O8 with a high surface area may be beneficial to lithium insertion between the V3O8 layers for application in batteries. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Oxalate‐Based 3D Chiral Magnets: The Series [ZII(bpy)3][ClO4][MIIFeIII(ox)3] (ZII = Fe, Ru; MII = Mn, Fe; bpy = 2,2'‐Bipyridine; ox = Oxalate Dianion)
Authors: Coronado Eugenio , Galán‐Mascarós José R. , Gómez‐García Carlos J. , Martínez‐Ferrero Eugenia , Almeida Manuel , Waerenborgh João C.
Published: June 2005

The synthesis, structure, and physical properties of the oxalate‐based molecular magnets with the formula [ZII(bpy)3][ClO4][MIIFeIII(ox)3] (ZII = Fe, Ru; MII = Mn, Fe; bpy = 2,2'‐bipyridine; ox = oxalate dianion) are presented here. All compounds are isostructural and crystallize in the chiral cubic space group P4132, and contain three‐dimensional dimetallic networks formed by alternating MII and MIII ions that are connected by oxalate anions. These compounds exhibit strong antiferromagnetic interactions that give rise to magnetic ordering as ferrimagnets or weak ferromagnets, with critical temperatures of up to 20 K, which is twice as high as those found for the isostructural magnets based on CrIII, as determined by magnetic measurements and Mössbauer spectroscopy. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthesis and Crystal Structures of Four Cyanide‐Bridged Coordination Polymers
Authors: He Xiang , Lu Can‐Zhong , Yuan Da‐Qiang , Chen Shu‐Mei , Chen Jiu‐Tong
Published: June 2005

The hydrothermal reaction of Cu(NO3)2·3 H2O, K3Fe(CN)6, and 1,10‐phenanthroline (1,10‐phen) or 2,2'‐bipyridine (2,2'‐bpy) gives rise to the three one‐dimensional helical‐chain complexes [Cu2Fe(CN)4(1,10‐phen)3]n·0.5n H2O (1), [Cu3(CN)3(1,10‐phen)3]n (2), and [Cu3(CN)3(2,2'‐bpy)3]n (3), and the two‐dimensional layer complex [Cu3Fe(CN)5(2,2'‐bpy)2]n (4). The structure of 1 contains a cyanide‐bridged CuI···FeII···CuI chain in which the two copper and one iron centers exhibit different coordination environments. The structures of 2 and 3 are both monometallic. Complex 4 is constructed alternately from fused 6‐ and 14‐metal‐membered nonplanar centrosymmetric rings that form a 2D layer architecture. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
1,3,5‐Triazapentadienes as Chelating Ligands: 1,2,4‐Triphenyl‐1,3,5‐triaza‐pentadiene Complexes of Cobalt(II), Nickel(II), Palladium(II), Copper(II) and Zinc(II)
Authors: Heße Nadine , Fröhlich Roland , Humelnicu Ionel , Würthwein Ernst‐Ulrich
Published: June 2005

1,2,4‐Triphenyl‐1,3,5‐triazapentadiene (1a), prepared from benzamidine and N‐phenylbenzimidoyl chloride, was treated at room temperature with CoCl2, Ni(NO3)2, Na2PdCl4, CuCl2 and ZnCl2 to form the corresponding six‐membered 1:1 chelate complexes 1a·CoCl2, 1a·Ni(NO3)2, 1a·PdCl2, 1a·CuCl2, and 1a·ZnCl2. In the solid state 1a·Ni(NO3)2 forms infinite linear chains, bridged by nitrate ions. From 1a and Cu(OTf)2 a 2:1 copper complex was obtained [(1a)2·Cu(OTf)2]. In all cases a proton shift from nitrogen atom N1 in the free ligand to N3 in the complex was observed. All complexes were completely characterized including X‐ray crystallography. Quantum chemical DFT calculations indicate that triazapentadiene is a better ligand for ZnCl2, PdCl2 and CuCl2 compared to ‐diimines and N‐acylamidines. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Towards Understanding of the Selective Precipitation of Alkali Metal Cations in Presence of Dipicrylamine Anion
Authors: Eringathodi Suresh , Agnihotri Pragati , Ganguly Bishwajit , Bhatt Pragnya , Sivagnana Subramanian Palani , Paul Parimal , Ghosh Pushpito K.
Published: June 2005

Dipicrylamine anion (DPA–) precipitates out [K(DPA)] with high selectivity from salt bitterns containing Na+, K+, and Mg2+, whereas the same ligand shows poor selectivity towards K+ – and much higher selectivity towards Cs+ – in studies conducted with a mixture of K+, Rb+, and Cs+. Their single‐crystal structures reveal that the K+ and Rb+ salts have similar layered structures, with 8 oxygen atoms from seven DPA– anions encapsulating the metal cation, whereas the Cs+ salt possesses a channel‐like structure with the metal ion encapsulated by ten oxygen atoms from six DPA–. The conformation of DPA– in the [Cs(DPA)] single crystal matches closely that of DPA in crystalline state. M···O and intermolecular C–H···O interactions together stabilize the structures. The 133Cs NMR spectrum of the poorly soluble [Cs(DPA)] shows an upfield shift of the peak with respect to CsCl as a result of the interaction with the oxygen atoms of DPA–, whereas 23Na NMR spectrum of the highly soluble [Na(DPA)] shows no such upfield shift compared to NaCl. Powder XRD patterns of bulk [M(DPA)] (M = K+, Rb+, and Cs+) precipitates show that these are similar to the patterns obtained by simulation of the single‐crystal X‐ray data. The selectivity of precipitation correlates qualitatively with the size and hydration enthalpies of the ions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Heterosite Effects in Novel Heteronuclear Clusters [Os2Ru(CO)11(PPh3)] and [Os2Ru(CO)10(2‐acetylpyridine‐N‐isopropylimine)]
Authors: Vergeer Frank W. , Lutz Martin , Spek Anthony L. , Calhorda Maria J. , Stufkens Derk J. , Hartl František
Published: June 2005

A new synthetic route towards the mixed‐metal cluster [Os2Ru(CO)12] is described together with the syntheses of its PPh3 and iPr‐AcPy (iPr‐AcPy = 2‐acetylpyridine‐N‐isopropylimine) derivatives. The molecular structures of the novel clusters [Os2Ru(CO)11(PPh3)] and [Os2Ru(CO)10(iPr‐AcPy)] were determined on the basis of crystalline solid solutions of the Os2Ru and corresponding Os3 species. The structures reveal that coordination of the Lewis bases occurs exclusively at the ruthenium site of [Os2Ru(CO)12], which is in agreement with density functional theory (DFT) calculations on several structural isomers of these compounds. According to the time‐dependent DFT results, the lowest optically accessible excited state of [Os2Ru(CO)10(iPr‐AcPy)] has a prevailing σ(Ru–Os2)π*(iPr‐AcPy) character, with a partial σσ*(Ru–Os2) contribution. In weakly coordinating 2‐chlorobutane, the excited state has a lifetime τ = 10.4 ± 1.2 ps and produces biradicals considerably faster than observed for [Os3(CO)10(iPr‐AcPy) (τ = 25.3 ± 0.7 ps). In coordinating acetonitrile, the excited state of [Os2Ru(CO)10(iPr‐AcPy)] decays mono‐exponentially with a lifetime τ = 2.1 ± 0.2 ps. In contrast to [Os3(CO)10(iPr‐AcPy)] that forms biradicals as the main primary photoproduct even in strongly coordinating solvents, zwitterion formation from the solvated lowest excited state is observed for the heterometallic cluster. This is concluded from time‐resolved absorption studies in the microsecond time domain. Due to the lower tendency of the coordinatively unsaturated +Ru(CO)2(iPr‐AcPy·–/0) moiety to bind a Lewis base, the heteronuclear biradical and zwitterionic photoproducts live significantly shorter than their triosmium counterparts. The influence of the weaker Os2–Ru(iPr‐AcPy) bond on the redox reactivity is clearly reflected in very reactive radical anions formed upon electrochemical reduction of [Os2Ru(CO)10(iPr‐AcPy)]. The dimer [–Os(CO)4‐Os(CO)4‐Ru(CO)2(iPr‐AcPy)]22– is the only IR‐detectable intermediate reduction product. The dinuclear complex [Os2(CO)8]2– and insoluble [Ru(CO)2(iPr‐AcPy)]n are the ultimate reduction products, proving fragmentation of the Os2Ru core. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthesis, Structure, and Ligand Redistribution Equilibria of Mixed Ligand Complexes of the Heavier Group 2 Elements Containing Pyrazolato andβ‐Diketiminato Ligands
Authors: El‐Kaderi Hani M. , Heeg Mary Jane , Winter Charles H.
Published: June 2005

Treatment of M[N(SiMe3)2]2(THF)2 (M = Ca, Sr, Ba) with various stoichiometries of N‐tert‐butyl‐4‐(tert‐butylimino)‐2‐penten‐2‐amine (LtBuH) and 3,5‐di‐tert‐butylpyrazole (tBu2pzH) afforded [(η2‐tBu2pz)Ca(μ‐η5:η2‐tBu2pz)(μ‐η2:η2‐tBu2pz)Ca(η5‐LtBu)] (17 %), [Sr(μ‐η5:η2‐tBu2pz)(η5‐LtBu)]2 (50 %), and [Ba(μ‐η5:η2‐tBu2pz)(η5‐LtBu)]2 (66 %) as colorless crystalline solids. The formulations of the new complexes were assigned from spectral and analytical data and by X‐ray crystal structure determinations. In the solid state, [(η2‐tBu2pz)Ca(μ‐η5:η2‐tBu2pz)(μ‐η2:η2‐tBu2pz)Ca(η5‐LtBu)] exists as a dimer that is held together by μ‐η5:η2‐ and μ‐η2:η2‐pyrazolato ligands, with a terminal η2‐tBu2pz ligand on one calcium ion and an η5‐LtBu ligand on the other. The dimeric structures of [Sr(μ‐η5:η2‐tBu2pz)(η5‐LtBu)]2 and [Ba(μ‐η5:η2‐tBu2pz)(η5‐LtBu)]2 are connected by two μ‐η5:η2‐pyrazolato ligands, and the coordination sphere of each metal ion is capped with an η5‐LtBu ligand. In toluene solution, [(η2‐tBu2pz)Ca(μ‐η5:η2‐tBu2pz)(μ‐η2:η2‐tBu2pz)Ca(η5‐LtBu)] exists as an equilibrium mixture of at least four compounds. In toluene solution, [Sr(μ‐η5:η2‐tBu2pz)(η5‐LtBu)]2 exists in equilibrium with Sr(η5‐LtBu)2 and Sr4(tBu2pz)8. A van’t Hoff analysis of this equilibrium between 46 and 104 °C afforded ΔH° = 22.2 ± 0.7 kcal/mol, ΔS° = 43.7 ± 1.9 cal/mol·K, and ΔG°(298 K) = 9.2 ± 0.9 kcal/mol. [Ba(μ‐η5:η2‐tBu2pz)(η5‐LtBu)]2 exists in toluene solution as a single, pure species between –60 and +80 °C. The overall results suggest that the η5‐LtBu ligand is better at saturating the coordination sphere of the metal ion to which it coordinates than is the tBu2pz ligand, and is suggested as a more promising ligand for the construction of practical, volatile chemical vapor deposition film growth precursors. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
First‐Row Transition Metal Bis(amidinate) Complexes; Planar Four‐Coordination of FeII Enforced by Sterically Demanding Aryl Substituents
Authors: Nijhuis Christian A. , Jellema Erica , Sciarone Timo J. J. , Meetsma Auke , Budzelaar Peter H. M. , Hessen Bart
Published: June 2005

The sterically hindered benzamidinate ligand [PhC(NAr)2]– (Ar = 2,6‐iPr2C6H3) has been employed to prepare bis(amidinate) complexes [{PhC(NAr)2}2M] of the divalent first‐row transition metals Cr–Ni (1–5). For Cr (planar), Mn and Co (tetrahedral) the observed structures follow the electronic preference for the metal ion in its highest spin multiplicity, as determined by DFT calculations. Remarkably, the Fe derivative adopts a distorted planar structure while retaining the high‐spin (S = 2) configuration. This rare combination is due to reduced interligand steric interactions in the planar vs. the tetrahedral structure, combined with a relatively small electronic preference of FeII for the tetrahedral environment. Thus, the simple bidentate ligand N,N'‐diarylbenzamidinate provides a convenient means to make this unusual species accessible for further study. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthesis and Characterisation of a Novel Copper(II) Azamacrocycle‐Phosphonate 3D Polymeric Network
Authors: Giambastiani Giuliano , Oberhauser Werner , Bianchini Claudio , Laschi Franco , Sorace Lorenzo , Brueggeller Peter , Gutmann Rene , Orlandini Annabella , Vizza Francesco
Published: June 2005

A new azamacrocycle phosphonate in its hydrocloride form (1) has been synthesized and characterised by multinuclear NMR spectroscopy and by a single X‐ray analysis. The reaction of 1 with CuII ions gives a polymeric compound (2), which exhibits an unprecedented three‐dimensional network containing two‐dimensional channels filled with guest molecules. The solid‐state structure of 2 and its properties have been characterised by means of various analytical methods which include single‐crystal X‐ray structure analysis, X‐ray powder diffraction, thermogravimetric studies as well as magnetic susceptibility and EPR measurements. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthesis, Molecular Structure and Reactivity of a Calix[4]arene Monomethyl Ether Supported Nitridomolybdenum Complex (Eur. J. Inorg. Chem. 11/2005)
Authors: Deplano Paola , Zeller Jürgen , Büschel Susanne , Reiser Benjamin K. H. , Begum Farida , Radius Udo
Published: June 2005

The cover picture shows the reaction of a calix[4]arene methyl ether stabilized nitridomolybdenum complex [MoN(MeCalix)] with GaCl3 to yield the compound [Mo(NGa‐Cl3)(MeCalix)]. This complex represents the first structurally characterized example of a nitrido‐bridged dinuclear compound of a group 6 metal and a group 13 halide [EX3]. Both metal atoms are unsymmetrically bridged with a short [Mo≡N] and a long [Ga−N] contact. Details on synthesis and structural characterization are discussed in the article by U. Radius et al. on p. 2037 ff. In the background there is a view from the University of Karlsruhe (TH) to the adjacent “Hardtwald” on a stormy day photographed by Bernhard Mühr (www.wolkenatlas.de).
Electrocatalytic Oxidation and Determination of Norepinephrine at Poly(Cresol Red) Modified Glassy Carbon Electrode
Authors: Chen Wei , Lin Xinhua , Luo Hongbin , Huang Liying
Published: June 2005

A glassy carbon electrode (GCE) was modified with electropolymerized films of cresol red in pH 5.6 phosphate buffer solution (PBS) by cyclic voltammetry (CV). The modified electrode shows an excellent electrocatalytic effect on the oxidation of norepinephrine (NE). The peak current increases linearly with the concentration of NE in the range of 3×10−6–3×10−5 M by the differential pulse voltammetry. The detection limit was 2×10−7 M. The modified electrode can also separate the electrochemical responses of norepinephrine and ascorbic acid (AA). The separation between the anodic peak potentials of NE and AA was 190 mV by the cyclic voltammetry. And the responses to NE and AA at the modified electrode were relatively independent.
The Influence of Rhodium(+3) onVoltammetry of Selenium(+4) in Perchloric Acid
Authors: Zelić Marina
Published: June 2005

In comparison with previously described voltammetric behavior of selenium(+4)–rhodium(+3) system in sulfuric or hydrochloric acid, results obtained in 0.1 mol/L perchloric acid differ significantly. The difference includes: a) number of signals and conditions under which they appear b) current‐concentration plots with nonzero intercepts c) unusual dependence of the peak characteristics on the speed of the applied technique and d) much more pronounced peak height enhancement. In square wave voltammetry the signal at −0.75 V can be even 230 times higher with rhodium(+3) than without it. Most probably the peak at −1.15 V corresponds to the catalytic reduction of hydrogen ions whereas the signal at −0.75 V is additionally influenced by some other processes. Results are highly dependent on the form of rhodium(+3) in the initial solution and qualitatively similar to those previously obtained with sulfur compounds and dissolved metal catalysts.
Gold Nanoparticle Modified Electrodes Show a Reduced Interference by Cu(II) in the Detection of As(III) Using Anodic Stripping Voltammetry
Authors: Dai Xuan , Compton Richard G.
Published: June 2005

Interference by Cu(II) causes serious problems in the detection of As(III) using anodic stripping voltammetry at gold electrodes. The behavior of Cu(II) and As(III) were examined at both a gold macro electrode and two kinds of gold nanoparticle modified electrodes, one where gold particles are deposited on glassy carbon (GC) and the other where basal plane pyrolytic graphite (BPPG) is the substrate. The sensitivity of As(III) detection was higher on gold nanoparticle modified electrodes than those on a macro gold electrode by up to an order of magnitude. In addition, the stripping peak of As(III) was narrower and more symmetric on a gold nanoparticle‐modified GC electrode, leading to analytical data with a lower limit of detection. At a macro gold electrode, the peak currents of Cu(II) were higher than those on gold nanoparticle modified electrodes. Accordingly, through the use of gold nanoparticle modified electrodes, the effect of copper interference to the arsenic detection can be reduced.
Differential Pulse Voltammetric Determination of Selenocystine Using Selenium‐gold Film Modified Electrode
Authors: Bai Yan , Yan Xiaoli , Li Rui , Zheng Wenjie , Yang Fang
Published: June 2005

Differential pulse voltammetric determination of selenocystine (SeC) using selenium‐gold film modified glassy carbon electrode ((Se‐Au)/GC) is presented. In 0.10 mol⋅L−1 KNO3 (pH 3.20) solution, SeC yields a sensitive reduction peak at −740 mV on (Se‐Au)/GC electrode. The peak current has a linear relationship with the concentration of SeC in the range of 5.0×10−8–7.0×10−4 mol⋅L−1, and a 3σ detection limit of SeC is 3.0×10−8 mol⋅L−1. The relative standard deviation of the reduction current at SeC concentration of 10−6 mol⋅L−1 is 3.88% (n=8) using the same electrode, and 4.19% when using three modified electrodes prepared at different times. The content of SeC in the selenium‐enriched yeast and selenium‐enriched tea is determined. The total selenium in ordinary or selenium‐enriched tea is determined by DAN fluorescence method. The results indicate that in selenium‐enriched yeast about 20% of total selenium is present as SeC and in selenium‐enriched tea SeC is the major form of selenoamino acids. The total selenium content in selenium‐enriched tea soup is 0.09 μgSe/g accounting by 7% compared with that in selenium‐enriched tea. Hence, only a little amount of selenium is utilized by drinking tea, and most selenium still stay in tealeaf. Uncertainty are 22.4% and 16.1% for determination of SeC in selenium‐enriched yeast and selenium‐enriched tea by differential pulse voltammetry (DPV) on (Se‐Au)/GC electrode, respectively.
Shaking table tests on reinforced concrete frames without and with passive control systems
Authors: Dolce Mauro , Cardone Donatello , Ponzo Felice C. , Valente Claudio
Published: June 2005

An extensive experimental program of shaking table tests on reduced‐scale structural models was carried out within the activities of the MANSIDE project, for the development of new seismic isolation and energy dissipation devices based on shape memory alloys (SMAs). The aim of the experimental program was to compare the behaviour of structures endowed with innovative SMA‐based devices to the behaviour of conventional structures and of structures endowed with currently used passive control systems.

This paper presents a comprehensive overview of the main results of the shaking table tests carried out on the models with and without special braces. Two different types of energy dissipating and re‐centring braces have been considered to enhance the seismic performances of the tested model. They are based on the hysteretic properties of steel elements and on the superelastic properties of SMAs, respectively.

The addition of passive control braces in the reinforced concrete frame resulted in significant benefits on the overall seismic behaviour. The seismic intensity producing structural collapse was considerably raised, interstorey drifts and shear forces in columns were drastically reduced. Copyright © 2005 John Wiley & Sons, Ltd.
Seismic demand sensitivity of reinforced concrete shear‐wall building using FOSM method
Authors: Lee Tae‐Hyung , Mosalam Khalid M.
Published: June 2005

The uncertainty in the seismic demand of a structure (referred to as the engineering demand parameter, EDP) needs to be properly characterized in performance‐based earthquake engineering. Uncertainties in the ground motion and in structural properties are responsible for EDP uncertainty. In this study, sensitivity of EDPs to major uncertain variables is investigated using the first‐order second‐moment method for a case study building. This method is shown to be simple and efficient for estimating the sensitivity of seismic demand. The EDP uncertainty induced by each uncertain variable is used to determine which variables are most significant. Results show that the uncertainties in ground motion are more significant for global EDPs, namely peak roof acceleration and displacement, and maximum inter‐storey drift ratio, than those in structural properties. Uncertainty in the intensity measure (IM) of ground motion is the dominant variable for uncertainties in local EDPs such as the curvature demand at critical cross‐sections. Conditional sensitivity of global and local EDPs given IM is also estimated. It is observed that the combined effect of uncertainties in structural properties is more significant than uncertainty in ground motion profile at lower IM levels, while the opposite is true at higher IM levels. Copyright © 2005 John Wiley & Sons, Ltd.
EEG alpha synchronization and functional coupling during top‐down processing in a working memory task
Authors: Sauseng Paul , Klimesch Wolfgang , Doppelmayr Michael , Pecherstorfer Thomas , Freunberger Roman , Hanslmayr Simon
Published: May 2005

Electroencephalogram (EEG) α (around 10 Hz) is the dominant rhythm in the human brain during conditions of mental inactivity. High amplitudes as observed during rest usually diminish during cognitive effort. During retention of information in working memory, however, power increase of α oscillations can be observed. This α synchronization has been interpreted as cortical idling or active inhibition. The present study provides evidence that during top‐down processing in a working memory task, α power increases at prefrontal but decreases at occipital electrode sites, thereby reaching a state in which α power and frequency become very similar over large distances. Two experimental conditions were compared. In the first, visuospatial information only had to be retained in memory whereas the second condition additionally demanded manipulation of the information. During the second condition, stronger α synchronization at prefrontal sites and larger occipital α suppression was observed as compared to that for pure retention. This effect was accompanied by assimilation of prefrontal and occipital α frequency, stronger functional coupling between prefrontal and occipital brain areas, and α latency shifts from prefrontal cortex to primary visual areas, possibly indicating the control of posterior cortical activation by anterior brain areas. An increase of prefrontal EEG α amplitudes, which is accompanied by a decrease at posterior sites, thus may not be interpreted in terms of idling or “global” inhibition but may enable a tight functional coupling between prefrontal cortical areas, and thereby allows the control of the execution of processes in primary visual brain regions. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
The emergence of the unmarked: A new perspective on the language‐specific function of Broca's area
Authors: Grewe Tanja , Bornkessel Ina , Zysset Stefan , Wiese Richard , von Cramon D. Yves , Schlesewsky Matthias
Published: May 2005

A number of neuroimaging studies have implicated an involvement of Broca's area, particularly of the pars opercularis of the left inferior frontal gyrus (IFG), in the processing of complex (permuted) sentences. However, functional interpretations of this region's role range from very general (e.g., in terms of working memory) to highly specific (e.g., as supporting particular types of syntactic operations). A dissociation of these competing accounts is often impossible because in most cases, the language internal complexity of permuted sentence structures is accompanied invariably by increasing costs of a more general cognitive nature (e.g., working memory, task difficulty, and acceptability). We used functional magnetic resonance imaging to explore the precise nature of the pars opercularis activation in the processing of permuted sentences by examining the permutation of pronouns in German. Although clearly involving a permutation operation, sentences with an initial object pronoun behave like simple, subject‐initial sentences (e.g., in terms of acceptability) because of a rule stating that pronouns should generally precede non‐pronominal arguments. The results of the experiment show that in contrast to non‐pronominal permutations, sentences with a permuted pronoun do not engender enhanced pars opercularis activation. Our findings therefore speak against both language‐related working memory and transformation‐based accounts of this region's role in sentence comprehension. Rather, we argue that the pars opercularis of the left IFG supports the language‐specific linearization of hierarchical linguistic dependencies. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Characterizing modulatory interactions between areas V1 and V2 in human cortex: A new treatment of functional MRI data
Authors: Friston K. J. , Ungerleider L. G. , Jezzard P. , Turner R.
Published: May 2005

Reversible cooling experiments in monkey visual cortex have demonstrated that visually driven neuronal activity in V2 depends on feedforward projections from V1, whereas neuronal activity in V1 is modulated by feedback, or reentrant, projections from V2. We present evidence for a homologous asymmetry in reciprocal connections between V1 and V2 in human cortex using physiological measurements obtained with functional MRI. The analysis was based on a nonlinear model of effective connectivity that partitioned the influence that one region exerted over another into an obligatory effect (an effect that depended only on the input) and a modulatory effect (an effect that represented an interaction between input and activity intrinsic to the target region). Using estimates of the modulatory effect we tested two related hypotheses: (1) that V2 would be a major source of modulatory influences on V1; and (2) that the modulatory effects of V2 on V1 would be greater than those of V1 on V2. The first constitutes a hypothesis about the regional or topographic organization of (modulatory) effective connectivity and the second hypothesis directly addresses the functional asymmetry suggested by reversible cooling experiments. The results confirmed that the origins of feedback modulatory effects on V1 were regionally specific and most pronounced in V2. In contrast, feedforward modulatory influences on V1 on V2 were negligible. This apparent asymmetry between feedforward and feedback modulatory interactions was evident in both hemispheres and appears to be a fairly robust feature of nonlinear interactions between striate and extrastriate cortex. © 1995 Wiley‐Liss, Inc.
Synthetic PET: Analyzing large‐scale properties of neural networks
Authors: Arbib M. A. , Bischoff A. , Fagg A. H. , Grafton S. T.
Published: May 2005

Synthetic PET is introduced as a new computational technique for connecting neural network studies based on animal data and image studies of human brain function. Synthetic PET comparisons are taken from a computational model of interacting neural networks in, for example, the monkey brain by integrating synaptic activity in each subnetwork as different simulated tasks are performed. Given a pair of tasks, comparative synaptic activity levels for each modeled neural region are then painted into the homologous regions of a three‐dimensional model of the human brain corresponding to the Talairach atlas. The resulting comparison then offers predictions of relative changes of neuronal activity as obtained from PET comparisons of humans performing a similar pair of tasks. Where neurophysiological data and individual arrays of neural networks give us a very fine‐grained view of the behavior of just a few neurons within nonhumans, PET measures provide a more global view of brain function. Synthetic PET allows us to integrate human and monkey studies in the construction of more complete models of the neural mechanisms used by both species in similar tasks. The technique is demonstrated in a saccade generation task. The method readily generalizes to other forms of brain imaging. © 1995 Wiley‐Liss, Inc.
Automatic 3‐D model‐based neuroanatomical segmentation
Authors: Collins D. Louis , Holmes C. J. , Peters T. M. , Evans A. C.
Published: May 2005

Explicit segmentation is required for many forms of quantitative neuroanatomic analysis. However, manual methods are time‐consuming and subject to errors in both accuracy and reproducibility (precision). A 3‐D model‐based segmentation method is presented in this paper for the completely automatic identification and delineation of gross anatomical structures of the human brain based on their appearance in magnetic resonance images (MRI).

The approach depends on a general, iterative, hierarchical non‐linear registration procedure and a 3‐D digital model of human brain anatomy that contains both volumetric intensity‐based data and a geometric atlas. Here, the traditional segmentation strategy is inverted: instead of matching geometric contours from and idealized atlas directly to the MRI data, segmentation is achieved by identifying the non‐linear spatial transformation that best maps corresponding intensity‐based features between a model image and a new MRI brain volume. When completed, atlas contours defined on the model image are mapped through the same transformation to segment and label individual structures in the new data set.

Using manually segmented sturcture boundaries for comparison, measures of volumetric difference and volumetric overlap were less than 2% and better than 97% for realistic brain phantom data, and less than 10% and better than 85%, respectively, for human MRI data. This compares favorably to intra‐observer variability estimates of 4.9% and 87%, respectively. The procedure performs well, is objective and its implementation robust. The procedure requires no manual intervention, and is thus applicable to studies of large numbers of subjects. The general method for non‐linear image matching is also useful for non‐linear mapping of brain data sets into stereotaxic space if the target volume is already in stereotaxic space. © 1995 Wiley‐Liss, Inc.
Characterization of acylcarnitines using fast atom bombardment mass spectrometry and gas chromatography/mass spectrometry
Authors: Van Bocxlaer J. F. , Claeys M. , Van Den Heuvel H. , De Leenheer A. P.
Published: May 2005

Mass spectral data are reported for an extended series of synthesized acylcarnitines. Direct mass spectrometry was performed using ionization by fast atom bombardment in combination with high‐energy collisional activation and B/E linked scanning. The data show that it is possible to distinguish between isomeric compounds using this technique. Gas chromatographic/mass spectrometric analysis data for acylcarnitines, as their acyloxylactone derivatives, are reported. Both electron impact and chemical ionization modes were used, permitting the unequivocal characterization and identification of the various compounds. In view of the recent marked increase in acylcarnitine profiling activities, the comprehensively reported mass spectrometric and gas chromatographic data may be useful for reference purposes.
Abstraction of multiple surface atoms by pyrazine, pyrene and HC2N ions on low‐energy collisions with self‐assembled monolayer surfaces
Authors: Riederer Donald E. , Cooks R. Graham , Linford Matthew R.
Published: May 2005

Ion/surface reactions of pyrazine and pyrene molecular ions and the HC2N+· ion were investigated using an alkyl self‐assembled monolayer surface consisting of hydrogenated and perdeuterated chains (CH3(CH2)15S–Au and CD3(CD2)15S–Au) intimately mixed in a 1:1 ratio. Each of these projectile ions is known to react upon collision at hydrocarbon‐covered surfaces, HC2N+· by abstraction of multiple hydrogen atoms and the pyrazine and pyrene molecular ions by abstraction of groups containing one or more carbon atoms. Data from the isotopically mixed surface show that pyrazine and pyrene abstract multiple carbon units from a single chain and that the units are transferred as intact alkyl units. The isotopic peak pattern arising from addition of two hydrogens to the HC2N+· ion on collision with the mixed surface differs from that expected from random addition of H and D, and the results indicate that multiple hydrogen atoms are abstracted from the same surface chain. Translational energy measurements on the ion/surface reaction products show that they leave the surface with very low kinetic energies (<5 eV).
Ionization processes in matrix‐assisted laser desorption/ionization mass spectrometry: Matrix‐dependent formation of [M + H]+ vs [M + Na]+ ions of small peptides and some mechanistic comments
Authors: Liao Pao‐Chi , Allison John
Published: May 2005

The relative signal intensities of [M + H]+ vs [M + Na]+ ions of some small peptides were found to be highly matrix‐dependent in matrix‐assisted laser desorption/ionization (MALDI) experiments when sinapinic acid, α‐cyano‐4‐hydroxycinnamic acid and 2,5‐dihydroxybenzoic acid were used as matrices. Presumably, this observation results from the competition of two different mechanisms for the ionization steps. Possible mechanisms for the formations of [M + H]+ and [M + Na]+ ions are proposed and discussed in the pursuit of defining the ionization step in MALDI. Several experiments were designed and performed for the further refinement of the mechanism. The results suggest that proton transfer from a matrix molecule to an analyte plays an important role in the ionization step. The transferring proton may be derived from photoionized or electronically excited matrix molecules. In contrast, some data are most consistent with a gas‐phase mechanism for [M + Na]+ ions.
Human α‐fetoprotein produced from hep G2 cell line: Structure and heterogeneity of the oligosaccharide moiety
Authors: Ferranti Pasquale , Pucci Pietro , Marino Gennaro , Fiume Immacolata , Terrana Benedetto , Ceccarini Costante , Malorni Antonio
Published: May 2005

The carbohydrate moiety of human α‐fetoprotein, an RMM 67000 glycoprotein produced in a hepatoma cell line (Hep G2), was investigated by the combined use of high‐resolution chromatographic techniques and mass spectrometry. Fast atom bombardment mass spectrometric (FABMS) and reversed‐phase high‐performance liquid chromatographic analysis of α‐fetoprotein obtained from a large‐scale cell culture following tryptic and peptide N‐glycanase F hydrolysis demonstrated that the protein contains a single glycosylation site at level of asparagine 232. Further, electrospray mass spectrometric measurement of the intact protein molecular mass showed that two main glycoforms are present. The complete definition of the structural heterogeneity of the oligosaccharide moiety was achieved by high‐performance anion‐exchange chromatography with pulsed amperometric detection together with carbohydrate mapping by FABMS of the released oligosaccharides demonstrating (i) that the glycosylation produced by cell culture is of the biantennary complex type typical of human hepatoma α‐fetoprotein and (ii) the presence of two main structures in a ratio of about 2:1 differing in the presence of a fucose residue in the N‐acetylglucosamine in the non reducing portion of the molecule.
Assay of the concentration and stable isotope enrichment of short‐chain fatty acids by gas chromatography/mass spectrometry
Authors: Powers Lisa , Osborn Melissa K. , Yang Dawei , Kien C. Lawrence , Murray Robert D. , Beylot Michel , Brunengraber Henri
Published: May 2005

Isotope dilution gas chromatographic mass spectrometric assays were developed for the concentration of shortchain fatty acids and of lactate in plasma. The assays involve spiking the samples with 2H‐ and/or 13‐C‐labeled internal standards and direct derivatization with 2,4‐difluoroaniline, using 1,3‐dicyclohexylcarbodiimide as a coupling agent. The assay can be used to determine the isotopic enrichment or mass isotopomer distribution of the fatty acids and of lactate. Blanks by ubiquitous formate, acetate and lactate are minimized by the one‐step derivatization procedure without deproteinization, using reagents dissolved in hydrocarbons. The assays were applied to experiments conducted in live dogs, pigs and monkeys, and in perfused rat livers. These techniques, in conjunction with appropriate stable isotope models, can be used to study carbohydrate fermentation in humans, ruminants and non‐ruminant mammals.
Fast atom bombardment mass spectra of dihydroxybenzenes: Formation of radical cation adduct between sample and matrix
Authors: Madhusudanan K. P.
Published: May 2005

Under fast atom bombardment, dihydroxybenzenes form predominantly the M+· and [M + Matrix]+· ions. The second field‐free region metastable decomposition of the [M + Matrix]+· ion involves the loss of a neutral molecule of the matrix. In the case of the hydroquinone–matrix adduct ion, elimination of both the matrix and hydroquinone are observed. Surprisingly, alkali metal cationization also leads to the formation of abundant radical cations in which the acidic hydrogens have been replaced with alkali metal. The degree of this exchange varies among the isomeric compounds. The facile formation of radical cations and their adducts appears to be due to various factors such as the ionization potentials, redox potentials and the proton affinities of the dihydroxybenzenes and the analyte‐matrix interactions.
Studies of the MALDI process by luminescence spectroscopy
Authors: Ehring Hanno , Sundqvist Bo U. R.
Published: May 2005

The process of matrix‐assisted laser desorption/ionization (MALDI) was investigated by studying the luminescence of matrix molecules induced by laser radiation. An optical multi‐channel analyser was utilized for the analysis of luminescence. The luminescence spectra of several MALDI matrices in the solid and liquid phase, the intensity and shape of the spectra at different temperatures, the intensity of the emitted light as a function of the laser fluences and the kinetics of the luminescence were investigated. Measurements of 2,5‐dihydroxybenzoic acid and ferulic acid at different temperatures allow the estimation of the average luminescence quantum yield, which is less than 0.2 at room temperature and the ionization threshold laser fluence. The low yield means that only a minor part of the absorbed energy is emitted. The major part of photon energy absorbed by the molecules relaxes by internal conversion and therefore contributes to the desorption/ionization process. At lower temperatures, the quantum yield increases significantly, which can explain the previously observed increase in the threshold fluence at lower temperatures. Time‐resolved measurements and the shape of the spectra indicate that the molecules investigated form excimers by laser irradiation. At laser fluences around the desorption threshold the luminescence is quenched, presumably by S1–S1 annihilation processes and/or phase transitions. The annihilation processes demonstrate that the electronically excited states are very mobile and interact with each other even at low exciton densities, i.e. laser fluences far below the ionization threshold laser fluence. The mobility can explain ion formation at laser fluences where two‐photon ionization in the gas phase is improbable. At low temperatures the quenching starts at lower laser fluences, which can be explained by the longer lifetimes of the excitons at these temperatures making interactions more probable. No long‐lived excited states, i.e. delayed fluoresecence or phosphorescence, were detected for 2,5‐dihydroxybenzoic acid and ferulic acid, whereas 3‐hydroxypicolinic acid emits photons up to 100 μs after the laser pulse.
How is the molecular ion of α‐tocopherol formed under fast atom bombardment conditions?
Authors: Takayama Mitsuo
Published: May 2005

The mechanism for the formation of the M+· ion of α‐tocopherol, a viscous oily material, under fast atom bombardment (FAB) conditions without a liquid matrix was investigated by using positive‐ and/or negative‐ion electron impact, gas‐phase FAB, gas‐phase fast molecule bombardment and charge‐exchange reaction techniques. The results obtained could not be explained by the charge exchange alone, and they also suggested that M+· ion formation under FAB conditions is not due to direct collisions between analytes and fast atoms but to collision interactions between analyte molecules in a dense gas‐like phase formed immediately after the collision cascade caused by particle bombardment and/or in the collision cascade itself. It is argued that the formation of M+· ions under matrix FAB conditions is essentially due to collision interactions between analyte and matrix molecules. In order to understand the M+· ion fromation, the energetics are discussed from the standpoint of the chargeexchange ionization reaction.
Determination of the calcium antagonist SIM6080 in plasma by gas chromatography/chemical ionization mass spectrometry
Authors: Castelnovo Pierfrancesco
Published: May 2005

A sensitive and selective gas chromatographic/mass spectrometric assay for the determination of the calcium antagonist SIM6080 in plasma was developed and validated. SIM6080 was extracted from plasma by a three‐step solvent extraction procedure and separated by capillary gas chromatography combined with mass spectrometric detection. Chemical ionization using ammonia as the reagent gas was used and the protonated molecular ion was monitored. The defluorinated analogue was used as an internal standard. The analysis of spiked plasma demonstrated good accuracy and precision of the assay with a quantitation limit of 0.5 ng ml−1 and a detection limit of 0.1 ng ml−1. The method was used for phase I pharmacokinetic studies.