1,721,022 research outputs found
The interplay of coordinative, hydrogen bonding and pi-pi stacking interactions in sustaining supramolecular solid-state architectures. A study case of bis(4-pyridyl)- and bis(4-pyridyl-N-oxide) tectons
No full textBis-monodentate ligands, such as bis(4-pyridyl) derivatives and bis(4-pyridyl-N-oxide), are able to generate polymetallic coordination networks with interesting supramolecular solid-state architectures. This review is devoted to high-dimensionality systems, which are extended by combining two or three organizing forces: metal-coordination, hydrogen bonds and pi-pi stacking interactions. A special emphasis is given to the following molecules, which play the role of linkers and spacers in the construction of extended frameworks: 4,4'-bipyridine, 1,2-bis(4-pyridyl)ethane, trans- 1,2-bis(4-pyridyl)ethene, trans-4,4'-azo-pyridine, 4,4'-bipyridyl-N,N'-dioxide. (C) 2002 Elsevier Science B.V. All rights reserved
Reinecke anion derivatives and homobinuclear complexes as tectons in designing heteropolymetallic systems
No full textCucos A, Avarvari N, Andruh M, Journaux Y, Müller A, Schmidtmann M. Reinecke anion derivatives and homobinuclear complexes as tectons in designing heteropolymetallic systems. EUROPEAN JOURNAL OF INORGANIC CHEMISTRY. 2006;2006(5):903-907
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A straightforward synthetic route towards tetranuclear copper(II) complexes: reactions between binuclear complexes and exo-bidentate or exo-bis(bidentate) ligands
No full textThe reactions between binuclear copper(II) complexes of the type [L(mu-OH)Cu-2](ClO4)(2) with exo-dentate ligands lead to tetranuclear complexes with both short and long distances between the metallic centers (L = the compartmental end-off ligand, 2,6bis[N-2-pyridylethyl)formimidoyl]-phenolato). Three new copper(II) complexes have been obtained by using the following spacers: bis(4-pyridyl)ethane (1), the dianion of the acetylenedicarboxylic acid (2) and 4,4'-bipyridine-N,N'-dioxide (3). The crystal structures of the three compounds have been solved. Compound 1 contains cationic [Cu-4] rectangles, with the short edges constructed from the preexisting p-OH and mu-phenoxo groups, and the long ones constructed from bis(4-pyridyl)ethane molecules. The crystal 2 contains centrosymmetric tetranuclear cationic species, which result by connecting two binuclear units with one dicarboxylato linker. Each carboxylato group forms a third bridge between the copper(II) ions within the binuclear moiety (syn -syn bridging more). In compound 3, one 4,4'-bipyridine-N,N'-dioxide molecule (4,4'-bpno) connects two copper(II) ions arising from two binuclear cationic entities. The two binuclear moieties are almost parallelly disposed above and below the 4,4'-bpno bridge. The Cu(II) ions bridged by 4,4'-bpno show a square-pyramidal stereochemistry, with the oxygen atom arising from 4,4'-bpno in the apical position. The other two copper(II) ions, which are not bridged by 4,4'-bpno, exhibit a square-planar coordination geometry. (C) 2002 Elsevier Science B.V. All rights reserved
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A new supramolecular multimetallic system containing three different spin-carriers
No full textA new heteropolynuclear supramolecular system with three different 3d paramagnetic metallic ions, [CuMnL(H2O)(2)][Cr(bipy)(C2O4)(2)]center dot 0.33 H2O (1), has been obtained by reacting K[Cr(2,2'-bipy)(C2O4)(2)] with [(LCuMnII)-Mn-II](ClO4)(2) (L2- is the anion of the Schiff-base resulted from the stepwise condensation of 2,6-diformyl-p-cresol with ethylenediamine and diethylenetriamine). The crystal structure was solved: compound I crystallizes in the monoclinic system, space group P 2(1), a = 10.3857(7) angstrom, b = 13.9015(6) angstrom, c = 19.134(11) angstrom, beta = 101.313(5)degrees. The analysis of the structural data reveals the formation of a 3D supramolecular network, developed by H-bonds, established between the aqua ligands and the oxalato groups of K[Cr(2,2'-bipy)(C2O4)(2)], and the pi-pi stacking interactions) between the aromatic fragments belonging to the 2,2'-bipy and L2- ligands (similar to 3.5 angstrom). The cryomagnetic investigation of 1 reveals an antiferromagnetic interaction between Cu-II and Mn-II within the compartmental ligand (J=-37 cm(-1)) and two uncoupled Cr(III) ions (S-Cr = 3/2). The nature of the ground state has been further confirmed by magnetization versus field measurements
The first coordination compound containing three different types of spin carriers: 2p-3d-4f (TCNQ(center dot-), Cu2+ and Gd3+)
No full textA novel heterospin system, [{CuL}(2)Gd(TCNQ)(2)].TCNQ- .CH3OH.2CH(3)CN, is obtained by reacting the mononuclear complex, [CuL], with gadolinium(III) nitrate, followed by the substitution of the nitrato ions with anionic organic radicals
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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