bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Supramolecular Properties of Trimethylene‐Bridged Clips
Authors: Klärner Frank‐Gerrit , Lobert Matthias , Naatz Ulf , Bandmann Heinz , Boese Roland 
Published: October 2003

AbstractThe novel trimethylene‐bridged clips 3 and 4 have been synthesized by using repetitive stereoselective Diels–Alder reactions of the benzo‐ and naphthobismethylenenorbornenes 8 and 19 as dienes and norbornadiene 9 as bisdienophile, and subsequent dehydrogenation of the primary cyclobisadducts 10 and 20 by using 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ). Clips 3 and 4 serve as receptors for a variety of electron‐deficient neutral and cationic aromatic substrates, comparable to the molecular tweezers 1 and 2. The thermodynamic parameters of the complex formation, Ka and ΔG, were determined by 1H NMR titration experiments and, in the case of the highly stable complex TCNB 32@4, by the use of isothermal titration microcalorimetry. The finding that clip 4 forms more stable complexes than 3 can be explained by the larger van der Waals contact surfaces of the naphthalene sidewalls in 4 compared to the corresponding benzene systems in 3. In the complexes with 4 as receptor, the plane of each aromatic substrate molecule is calculated to be oriented almost parallel to the naphthalene sidewalls. However, in the complexes of tweezers 2, the substrate is usually oriented parallel to the central naphthalene spacer unit. Due to the more open topology of 4, most complexes were calculated to consist of two or more equilibrating noncovalent conformers.
The Open‐Chain Trioxide CF3OC(O)OOOC(O)OCF3
Authors: von Ahsen Stefan , García Plácido , Willner Helge , Burgos Paci Maximiliano , Argüello Gustavo A. 
Published: October 2003

AbstractThe open‐chain trioxide CF3OC(O)OOOC(O)OCF3 is synthesised by a photochemical reaction of CF3C(O)OC(O)CF3, CO and O2 under a low‐pressure mercury lamp at −40 °C. The isolated trioxide is a colourless solid at −40 °C and is characterised by IR, Raman, UV and NMR spectroscopy. The compound is thermally stable up to −30 °C and decomposes with a half‐life of 1 min at room temperature. Between −15 and +14 °C the activation energy for the dissociation is 86.5 kJ mol−1 (20.7 kcal mol−1). Quantum chemical calculations have been performed to support the vibrational assignment and to discuss the existence of rotamers.
Photochromism of Diarylethenes Linked by Hydrogen Bonds in the Single‐Crystalline Phase
Authors: Yamamoto Satoshi , Matsuda Kenji , Irie Masahiro 
Published: October 2003

AbstractPhotochromic diarylethenes, which bear carboxyl groups at the ortho, meta, or para positions of both terminal phenyl groups, have been synthesized. The diarylethenes adopt linear chain structures as a result of hydrogen bonding in the crystalline phase, and the crystals exhibit photochromic properties. The absorption maximum of the photogenerated closed‐ring isomer of the para‐substituted derivative shows an 80 nm bathochromic shift in comparison with that of the ortho‐substituted derivative. The maximum of the closed‐ring isomer of the meta‐substituted derivative is located in between those of the para‐ and ortho‐substituted derivatives. The shifts can be attributed to the differences in conformation among the derivatives, arising from the restrictions imposed by the hydrogen‐bonded chains.
Synthetic and Structural Studies of Cobalt–Pivalate Complexes
Authors: Aromí Guillem , Batsanov Andrei S. , Christian Paul , Helliwell Madeleine , Parkin Andrew , Parsons Simon , Smith Andrew A. , Timco Grigore A. , Winpenny Richard E. P. 
Published: October 2003

AbstractThe synthesis and characterisation of a range of cobalt pivalate cage complexes are reported. The cages include: a dinuclear CoII complex; an oxo‐centred CoIII triangle; tetranuclear CoII heterocubanes and butterflies; tetranuclear heterovalent cobalt butterflies and hexanuclear edge‐sharing bitetrahedra; heterovalent penta‐, hexa‐ and hepta‐nuclear cages based on {M4O4} heterocubane cores; and a tetradecanuclear cage based on heterocubanes sharing edges and vertices. Spectroscopic studies suggest that some of these cores are retained in solution, but that only in the CoIII triangle is the structure including ligands retained. A scheme is proposed to account for the many structures observed, which may be applicable to other polymetallic cage complexes.
Modulating Charge‐Transfer Interactions in Topologically Different Porphyrin–C60 Dyads
Authors: Guldi Dirk M. , Hirsch Andreas , Scheloske Michael , Dietel Elke , Troisi Alessandro , Zerbetto Francesco , Prato Maurizio 
Published: October 2003

AbstractControl over the interchromophore separation, their angular relationship, and the spatial overlap of their electronic clouds in several ZnP–C60 dyads (ZnP=zinc porphyrin) is used to modulate the rates of intramolecular electron transfer. For the first time, a detailed analysis of the charge transfer absorption and emission spectra, time‐dependent spectroscopic measurements, and molecular dynamics simulations prove quantitatively that the same two moieties can produce widely different electron‐transfer regimes. This investigation also shows that the combination of ZnP and C60 consistently produces charge recombination in the inverted Marcus region, with reorganization energies that are remarkably low, regardless of the solvent polarity. The time constants of electron transfer range from the μs to the ps regime, the electronic couplings from a few tens to several hundreds of cm−1, and the reorganization energies remain below 0.54 eV and can be as low as 0.16 eV.
Remarkable Reactions of Cyclooctatetraene Diiron‐Bridging Carbyne Complexes with Amino and Amido Compounds: Nucleophilic Addition to and Breaking of the Cyclooctatetraene Ring
Authors: Zhang Shu , Xu Qiang , Sun Jie , Chen Jiabi 
Published: October 2003

AbstractThe reactions of the cationic, diiron‐bridging carbyne complexes [Fe2(μ‐CAr)(CO)4(η8‐C8H8)]BF4 (1, Ar=C6H5; 2, Ar=p‐CH3C6H4; 3, Ar=p‐CF3C6H4) with LiN(C6H5)2 in THF at low temperature gave novel N‐nucleophilic‐addition products, namely, the neutral, diiron‐bridging carbyne complexes [Fe2(μ‐CAr)(CO)4(η7‐C8H8N(C6H5)2)] (4, Ar=C6H5; 5, Ar=p‐CH3C6H4; 6, Ar=p‐CF3C6H4)). Cationic bridging carbyne complexes 1–3 react with (C2H5)2NH, (iC3H7)2NH, and (C6H11)2NH under the same conditions with ring cleavage of the COT ligand to produce the novel diiron‐bridging carbene inner salts [Fe2{μ‐C(Ar)C8H8NR2}(CO)4] (7, Ar=C6H5, R=C2H5; 8, Ar=p‐CH3C6H4, R=C2H5; 9, Ar=p‐CF3C6H4, R=C2H5; 10, Ar=C6H5, R=iC3H7; 11, Ar=p‐CH3C6H4, R=iC3H7; 12, Ar=p‐CF3C6H4, R=iC3H7; 13, Ar=C6H5, R=C6H11; 14, Ar=p‐CH3C6H4, R=C6H11, 15, Ar=p‐CF3C6H4, R=C6H11). Piperidine reacts similarly with cationic carbyne complex 3 to afford the corresponding bridging carbene inner salt [Fe2{μ‐C(Ar)C8H8N(CH2)5}(CO)4] (16). Compound 9 was transformed into a new diiron‐bridging carbene inner salt 17, the trans isomer of 9, by heating in benzene. Unexpectedly, the reaction of C6H5NH2 with 2 gave a novel COT iron–carbene complex [Fe2{C(C6H4CH3‐p)NHC6H5}(μ‐CO)(CO)3(η8‐C8H8)] (18). However, the analogous reactions of 2‐naphthylamine with 2 and of p‐CF3C6H4NH2 with 3 produce novel chelated iron–carbene complexes [Fe2{C(C6H4CH3‐p)NC10H7}(CO)4(η2:η3:η2‐C8H9)] (19) and [Fe2{C(C6H4CF3‐p)NC6H4CF3‐p}(CO)4(η2:η3:η2‐C8H9)] (20), respectively. Compound 18 can also be transformed into the analogous chelated iron–carbene complex [Fe2{C(C6H4CH3‐p)NC6H5}(CO)4(η2:η3:η2‐C8H9)] (21). The structures of complexes 6, 9, 15, 17, 18, and 21 have been established by X‐ray diffraction studies.
Unexpected Reaction Pathways in the Reaction of Alkoxyalkynylchromium(0) Carbenes with Aromatic Dinucleophiles
Authors: Sierra Miguel A. , Mancheño María J. , del Amo Juan C. , Fernández Israel , Gómez‐Gallego Mar 
Published: October 2003

AbstractThermal‐ or SiO2‐induced reactions of the Michael adducts of 1,2‐aromatic dinucleophiles and alkynylchromium(0) carbene complexes, compounds 7–10, form different products in good yields depending on the nature of the aromatic dinucleophile used. Thus, 1,2‐diaminobenzene derivatives 7 and 8 rearrange to pentacarbonylchromium(0) isocyanide complexes 11, 12, 14, and 15 in a process that occurs through bicyclic intermediates 24. Adducts 9 derived from o‐aminophenol give 2,3‐dihydro‐1,5‐benzoxazepine derivatives 17 by intramolecular 1,2‐addition, followed by protonation at the chromium center and reductive elimination. In contrast, base‐promoted addition of the phenolic hydroxy group in compound 9 a affords 3‐ethoxy‐5‐phenyl‐5,6‐dihydro‐2H‐1,6‐benzoxazocin‐2‐one (18), together with the expected adduct 17 a. Compound 18 is formed by a nucleophilic addition to a CO ligand in a preformed carbene complex. This is a new example of the rare attack of a nucleophile on a CO ligand in a Fischer carbene complex. Adducts 10 form seven‐membered‐ring carbene complexes 19 and 20 by intramolecular aminolysis. In contrast, reaction of alkynyl carbene complexes with 1,8‐diaminonaphthalene under very mild conditions leads to 2‐substituted perimidines 33 together with the corresponding ethoxymethylmetal carbene complex 32 through an unprecedented fragmentation process in a formal retro‐Aumann reaction.
Systematic Construction of a Monotetrahydrofuran‐Ring Library in Annonaceous Acetogenins by Asymmetric Alkynylation and Stereodivergent Tetrahydrofuran‐Ring Formation
Authors: Kojima Naoto , Maezaki Naoyoshi , Tominaga Hiroaki , Asai Mikito , Yanai Minori , Tanaka Tetsuaki 
Published: October 2003

AbstractAll eight diastereoisomers of the monotetrahydrofuran‐ring cores of annonaceous acetogenins have been synthesized through utilization of asymmetric alkynylation and stereodivergent one‐pot tetrahydrofuran‐ring formation. In all cases, the asymmetric alkynylation proceeded with very high diastereoselectivity to give eight kinds of optically pure tetrahydrofuran core from a common α‐oxyaldehyde. We also describe a comparison of the 1H NMR, 13C NMR, and CD spectral data of the eight isomers and give full details of the tetrahydrofuran‐ring construction including a model study of asymmetric alkynylation.
Cover Picture: Aromaticity and Electron Affinity of Carbok‐[3]radialenes, k=0, 1, 2 (Chem. Eur. J. 20/2003)
Authors: Lepetit Christine , Brøndsted Nielsen Mogens , Diederich François , Chauvin Remi 
Published: October 2003

AbstractThe cover picture shows the doubly charged (q=−2) buta‐1,3‐diynediyl expanded [3]radialene. The question whether aromaticity enhancement a possible driving force for the facile reduction of some expanded [3]radialenes has been explored. The theoretical study on a series of [3]radialenes with endocyclic and/or peripheral carbo‐meric expansion leads to a generalization of the simple 4n+2 πz Hückel rule to such “electronic roundabouts” with three possible “exits”. Thus, the doubly charged (q=−2) buta‐1,3‐diynediyl expanded [3]radialene shown contains 14 πz electrons in the cross‐conjugated ring and exhibits according to the calculations both magnetic and geometrical aromaticity. For more details see the article by R. Chauvin et al. on p. 5056 ff.
Pseudopotential theory of a partially ionized hydrogen plasma
Authors: Arkhipov Yu.V. , Baimbetov F.B. , Davletov A.E. 
Published: October 2003

AbstractIn the framework of the BBGKY hierarchy the main features of interparticle interactions in a partially ionized hydrogen plasma are extensively studied. The theory developed is quite analogous to the Debye‐Hückel approximation of a fully ionized plasma. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Static and dynamic properties of 2‐dimensional strongly coupled Yukawa liquids
Authors: Donkó Z. , Hartmann P. , Kalman G. J. , Rosenberg M. 
Published: October 2003

AbstractStatic and dynamical properties of strongly coupled Yukawa liquids are investigated. The particles are either (i) situated within an ideal 2‐dimensional plane or (ii) are confined by an external parabolic potential to form a quasi‐2‐dimensional configuration. The static simulations (yielding pair correlation functions and correlation energies) and dynamical simulations (yielding spectra of density and current fluctuations) are carried out for a wide range of coupling (Γ) and screening (κ) parameters. The dispersion relations show good agreement with the predictions of the QLCA theory. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Plasma phase transition in hydrogen and electron‐hole plasmas
Authors: Filinov V. , Bonitz M. , Levashov P. , Fortov V. , Ebeling W. , Schlanges M. 
Published: October 2003

AbstractThe plasma phase transition in dense hydrogen and in electron‐hole plasmas is investigated by direct path integral Monte Carlo simulations. Hydrogen results for the internal energy at T = 10, 000 K show a deep minimum and strong fluctuations around the density n = 1023 cm−3 indicating the existence of a phase transition. To verify this explanation, the analogous phenomenon is studied for an electron‐hole plasma in Germanium. The calculated phase boundary of the electron‐hole liquid is found to agree reasonably well with the available experimental data. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fluid metals in the liquid‐vapour critical region
Authors: Hensel F. , Pilgrim W.‐C. 
Published: October 2003

AbstractExperimental results in the liquid vapour critical region of metals show that the metal‐nonmetal transition noticeably influences, the electronic, thermodynamic, structural, dynamic and interfacial features of fluid metals. The main emphasis of the paper is on the intimate interplay between the changes in interparticle forces and the changes in the electronic structure associated with the pressure ionization. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Equation of state for dense plasmas
Authors: Kuhlbrodt S. , Juranek H. , Schwarz V. , Redmer R. 
Published: October 2003

AbstractThe composition and equation of state of dense fluids and plasmas is calculated within the chemical picture. While dissociation is important for molecular fluids such as hydrogen, the excitation of higher ionization stages is relevant for e. g. noble gases and metal plasmas. Results for the Hugoniot curves of hydrogen‐helium mixtures which are relevant for astrophysical applications are shown. The composition of beryllium plasma at solid statelike densities and at temperatures of several eV is determined and compared with new experimental results. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fokker‐Planck equation with velocity‐dependent coefficients: Application to dusty plasmas and active particles
Authors: Trigger S.A. , Ebeling W. , Ignatov A.M. , Tkachenko I.M. 
Published: October 2003

AbstractSelf‐consistent and universal description of friction and diffusion for Brownian particles in such various systems as dusty plasma and active particles (e.g., cells in biological systems) is presented. Generalized friction function is determined to describe the friction force itself as well as a drag force in the case of non‐zero driven ion velocity in plasmas. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic response of two‐component model plasmas
Authors: Zwicknagel G. , Pschiwul Th. 
Published: October 2003

AbstractThe dynamic structure factor of a two‐component model plasma, where the Coulomb interaction is regularized at short distances, is investigated in molecular dynamics simulation studies. Special attention is paid to the dependency of the dynamic response on a variation of the used effective interaction and a test of the accuracy of the predictions made by diverse theoretical treatments. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Complete maternal deprivation affects social, but not spatial, learning in adult rats
Authors: Lévy F. , Melo A. I. , Galef B. G. , Madden M. , Fleming A. S. 
Published: October 2003

AbstractThe effects of maternal deprivation on learning of social and spatial tasks were investigated in female adult rats. Pups were reared artificially and received “lickinglike” tactile stimulation (AR animals) or were reared with their mothers (MR animals). In adulthood, subjects were tested on paradigms of spatial learning and on paradigms involving learning of social cues. Results showed that maternal deprivation did not affect performance on spatial learning, but it did impair performance on the three social learning tasks. The AR animals made no distinction between a new and a previously presented juvenile conspecific. AR animals also responded less rapidly than MR animals at test for maternal behavior 2 weeks after a postpartum experience with pups. Finally, AR animals did not develop a preference for a food previously eaten by a familiar conspecific whereas MR animals did. This study indicates that animals reared without mother and siblings show no deficits in spatial tasks while showing consistent deficits in learning involving social interactions. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 43: 177–191, 2003.
Arousal, but not nursing, is necessary to elicit a decreased fear reaction toward humans in rabbit (Oryctolagus cuniculus) pups
Authors: Pongrácz Péter , Altbäcker Vilmos 
Published: October 2003

AbstractRabbits that are handled at the time of feeding during the first week postpartum show reduced fear of humans later in their lives as compared to unhandled controls. Effective handling has been shown to be confined to a sensitive period. Our study aimed to investigate if feeding itself (provided by a second doe, 6 hr after the standard nursing time) affects the levels of fear of humans later in life. Our results showed that (a) the prenursing state of excitement is only characteristic of the standard nursing and is not elicited by a second feeding 6 hr past the usual nursing time, repeated daily across the first week postpartum; and (b) handling linked to a second feeding 6 hr after the standard nursing does not reduce fear responses toward humans at weaning. We conclude that the aroused state, per se, is essential for the reduction of a rabbit's fear response toward humans provoked by early handling. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 43: 192–199, 2003.
Retrieval difficulty and retention of reactivated memories over the first year of life
Authors: Hildreth Karen , Hill Debra 
Published: October 2003

AbstractA newly acquired memory is remembered longer when its retrieval is more difficult (i.e., when the time since the last retrieval is longer). In two experiments using an operant conditioning task with 198 infants between 3 and 12 months of age, we presently asked if a reactivated memory also is remembered longer when its retrieval is more difficult. During their first year, infants remember a memory reactivated 1 week after forgetting and the newly acquired memory equally as long. After determining the upper limit (UL) of reactivation at all ages (Experiment 1), we reactivated the memory near the UL and then measured its subsequent persistence (Experiment 2). We found that increasing the training‐reactivation interval enhanced retention at 6 months only. These data reveal that increasing retrieval difficulty affects infants' retention of newly acquired and reactivated memories differently. More generally, memory reactivation seems to disproportionately benefit retention in younger infants. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 43: 216–229, 2003.
Application of a novel polypropylene to the insulation of an electric power cable
Authors: Yoshino Katsumi , Demura Tsuyoshi , Kawahigashi Masaki , Miyashita Yoshitsugu , Kurahashi Kiyoshi , Matsuda Yoshiji 
Published: October 2003

AbstractCross‐linked polyethylene (XLPE) has been widely adopted as insulating material for high‐voltage power cables up to 500 kV. Further improvement of electrical and thermal properties on insulating material is required in order to increase cable operation efficiency. Therefore, the development of novel insulating material possessing high thermal properties will be necessary.Recent progress of catalysis technology contributes to obtain new polymeric materials which may be applied to electrical insulation. The authors investigated the basic properties of newly developed stereoregular syndiotactic polypropylene (s‐PP) which is synthesized with homogeneous metallocene catalyst. Though recycling of cross‐linked polymers such as conventionally used XLPE may be difficult because of their poor heat deformation, the s‐PP which is not cross‐linked must be suitable for recycling.A series of experiments on its physical and electrical properties gave the following results.

s‐PP has sufficient flexibility compared with isotactic polypropylene (i‐PP ).
Both AC and lightning impulse breakdown strength of s‐PP in spite of no cross‐linking are superior to those of XLPE in the temperature range from 25 to 90 °C.
Degradation by copper of s‐PP is less than that of i‐PP.
s‐PP/VLDPE blend shows sufficient brittleness temperature for use.
These results suggested that s‐PP should serve as insulating material for power cables at higher‐temperature operation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 18–26, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002//eej.10210
Countermeasures for controlling lightning‐caused overvoltage on indoor wiring with communication line
Authors: Nakada Kazuo , Sugimoto Hitoshi , Shimada Seiichi , Asaoka Yoshinobu , Asakawa Akira 
Published: October 2003

AbstractOvervoltage generated by lightning is a threat to indoor electrical equipment in our information‐oriented and computerized society. Countermeasures for preventing overvoltage on indoor wiring are demanded. Therefore, we have investigated the effectiveness of some countermeasures, such as low‐voltage arresters, communication line arresters, SPDs, and a common grounding wire, for reducing the overvoltage on indoor wiring with a communication line. In particular, we have studied the effect of the combination of these countermeasures and their layout on controlling the overvoltage, using a full‐scale test distribution line with a customer's facility. The main results are as follows:

A common grounding wire installed along the low‐voltage indoor wiring is more effective for reducing the overvoltage on the indoor wiring with a communication line than is one installed under the floor, when the arresters are installed at the panel board.
Combination of an SPD and other countermeasures, such as low‐voltage arresters and a common grounding wire, is effective for controlling the overvoltage on the indoor wiring, and the effectiveness of these countermeasures for preventing damage of electrical equipment has been verified by an experiment using actual electrical equipment. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 37–45, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10223
Environmental assessment of the EU Structural Funds: the German Objective 1 regional development plan and Berlin operational programme
Authors: Fischer Thomas B. 
Published: October 2003

AbstractWhilst the assessment of environmental impacts should form an integral part of EU Structural Fund documentation, to date the extent to which this has happened has largely remained unclear. Addressing this shortcoming, the paper looks at recent practice in the German Objective 1 areas. In this context, the regional development plan of the ‘new’ German Länder and the operational programme for the Eastern part of Berlin are analysed, using the EU Structural Fund SEA (strategic environmental assessment) Handbook, the ‘SEA Directive’ (2001/42/EC) and SEA ‘good practice’ criteria, as proposed in the professional literature. It is found that whilst some SEA aspects are considered in current practice, there is scope for improvement, particularly in terms of an early integration of the assessment in the plan making process, a better consideration of alternatives, a wider consultation process, the preparation of a separate EA report and more transparent plan approval. Copyright © 2003 John Wiley & Sons, Ltd and ERP Environment.