1,721,041 research outputs found
One-Pot Synthesis of a New Magnetically Coupled Heterometallic Cu2Mn2 [2 x 2] Molecular Grid
No full textThe heterometallic [2 x 2] grid-type complex [Cu2Mn2(pop)(4)(OAc)(4)]center dot 7H(2)O (1) has been selectively synthesized in a targeted one-pot reaction. Single-crystal X-ray analysis shows the expected structure with identical metal ions located at diagonal vertices of the grid. Magnetochemical studies reveal that 1 has a ferrimagnetic spin ground state with some admixture of low-lying excited states.DFG [SFB 602
New copper(II) 1D polymer containing dimethyl(phenylsulfonyl)amidophosphate: Synthesis, crystal structure and magnetic properties
No full textThe reaction of sodium dimethyl(phenylsulfonyl)amidophosphate NaL (HL=C(6)H(5)SO(2)NHP(O)(OCH(3))(2)) with Cu(NO(3))(2) center dot 6H(2)O and o-bpe (1,2-bis(pyridine-2-yl)ethane) in appropriate ratios, afford the formation of 1D coordination polymer [Cu(L)(2) center dot o-bpe](n) in good yield. The crystal structures of HL (1) and [Cu(L)(2) center dot o-bpe](n) (2) are reported. In the crystal package the molecules of 1 are linked by intermolecular hydrogen bonds formed by the phosphoryl oxygen atoms which serve as acceptors and nitrogen atoms of amide groups as donors. The crystal structure of 2 indicates the presence of unsaturated Cu(L)(2) unit bridged by o-bpe ligand in the one-dimensional polymeric chain. The Cu(II) atoms have distorted 4 + 2 octahedral CuO(4)N(2) environment formed by the oxygen atoms belonging to the sulfonyl and phosphoryl groups of two deprotonated chelate ligands and nitrogen atoms of the bridging o-bpe ligands. The magnetic study of 2 has revealed the presence of a weak intrachain antiferromagnetic exchange interaction between copper ions. (C) 2009 Elsevier Ltd. All rights reserved.Fundamental Researches State Fund of Ukraine [F25/193 - 2008
Regular High-Nuclearity Species from Square Building Blocks: A Triangular 3 x [2 x 2] Ni-12 Complex Generated by the Self-assembly of Three [2 x 2] Ni-4 Molecular Grids
No full textA dodecanuclear 3 x [2 x 2] nickel(II) complex has been obtained via the self-association of three tetranuclear [2 x 2] molecular grids. X-ray diffraction shows a "propeller-like" structure of the [Ni-4](3) scaffold with a central mu(3)-hydroxide. The dodecanuclear species remains stable in solution and can be deposited without decomposition on highly ordered pyrolytic graphite surfaces
Synthesis and structure of [2 x 2] molecular grid copper(II) and nickel(II) complexes with a new polydentate oxime-containing Schiff base ligand
No full textA new polynucleating oxime-containing Schiff base ligand, 2-hydroxyimino-N'-[1-(2-pyridyl)ethylidene]propanohydrazone (Hpop), has been synthesized and fully characterized. pH potentiometric, electrospray ionization mass spectrometric, and spectrophotometric studies of complex formation in H(2)O/DMSO solution confirmed the preference for polynuclear complexes with 3d metal ions. Single-crystal X-ray diffraction analyses of [Ni(4)(pop)(4)(HCOO)(4)]center dot 7H(2)O (1), [Cu(4)(pop-H)(4)(HCOOH)(4)] center dot H(2)O (2), and [Cu(4)(pop-H)(4)(H(2)O)(4)] center dot 9H(2)O (3) indicated the presence of a [2 x 2] molecular grid structure in all three compounds but distinct configurations of the cores: a head-to-tail ligand arrangement with overall S(4) symmetry of the grid in the Cu(2+) complexes as opposed to a head-to-head ligand arrangement with (noncrystallographic) O(2) grid symmetry for the Ni(2+) complex. A cryomagnetic study of 3 revealed intramolecular ferromagnetic exchange between copper ions in the grid, while in 1, antiferromagnetic interactions between the metal ions were observed
Novel pyrazolate-based copper(II) [2 x 2] grid complexes: Synthesis, structure and properties
No full text5-Acetyl-substituted pyrazole-3-carboxylic acid (H2L) forms [2 x 2] grid-like tetranuclear Cu(II) complexes with four five-coordinated copper(II) ions bridged by pyrazolate groups. Despite a significant dissociation of [Cu4L4(H2O)(4)]center dot 4H(2)O (1) in aqueous solution(1), it was possible to substitute the coordinated water molecules by pyridine ligands or azide anions. The resulting tetranuclear complexes [Cu4L4Py4]center dot 2H(2)O (2) and Na-4[Cu4L4(N-3)(4)]center dot 7MeOH (3) were isolated and studied by X-ray diffraction analysis. In 2 and 3 the azide anions or pyridine molecules complete the distorted square-pyramidal coordination of each copper(II) center. Magnetic susceptibilities of the obtained compounds have been measured by SQUID techniques. Simulation of the data using a Heisenberg spin Hamiltonian approach showed that the bridges between the metals mediate weak intramolecular antiferromagnetic coupling (J in the range -13.3 to -17.1 cm (1)) and lead to a singlet ground state in all cases. (C) 2012 Elsevier B.V. All rights reserved
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
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
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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