1,721,015 research outputs found
Homoleptic metal complexes of 4'-(5-pyrimidinyl)-2,2':6',2''-terpyridine : tetrafurcated expanded ligands
No full textWith iron(II) and ruthenium(II), 4`-(5-pyrimidinyl)-2,2`: 6`,2 ``-terpyridine (L) preferentially coordinates through the tpy domain to give octahedral [ML2](2+) (M Fe, Ru) complexes. Treatment of [RuL2][PF6](2) with CuCl2 center dot 2H(2)O leads to [Ru(2)(2)][CuCl2(OH2)][CuCl3]Cl center dot 3MeCN center dot 7H(2)O(n) which exhibits a two-dimensional coordination network with copper(II) centres interconnecting [RuL2](2+) motifs. Magnetic susceptibility data for the material are consistent with a one-dimensional S = 1/2 antiferromagnetic chain
Structural diversity in the reactions of 4 '-(pyridyl)-2,2 ':6 ',2 ''-terpyridine ligands and bis{4 '-(4-pyridyl)-2,2 ':6 ',2 ''-terpyridine}iron(II) with copper(II) salts
No full textWe have demonstrated that treatment of [Fe(1)(2)](2+) (1 = 4'-(4-pyridyl)-2,2':6',2 ''-terpyridine) with an excess of CuCl2 center dot 2H(2)O leads to competition between coordination of copper(II) by the pendant pyridine donors in [Fe(1)(2)](2+), and transfer of ligand 1 from iron(II) to copper(II) to yield [{Cl3Cu(mu-1)Fe(mu-1)}(2)CuCl2(OH2)(2)]Cl-2 center dot 4H(2)O and [Cu(H1)Cl-2]Cl center dot 4H(2)O, respectively. Direct reaction of 1 with CuCl2 center dot 2H(2)O and variation in crystallization conditions results in the formation of either monomeric or polymeric complexes: [Cu(1)Cl-2]center dot 4.75H(2)O, [Cu(1)Cl-2]center dot H2O center dot MeOH and [Cu(1)Cl-2 center dot 2H(2)O](n). The reaction of 1 with Cu(NO3)(2)center dot 3H(2)O gives the coordination polymer [Cu(1)(ONO2)(2)center dot H2O](n). Magnetic data for [Cu(1)Cl-2 center dot 2H(2)O](n) and [Cu(1)(ONO2)(2)center dot H2O](n) are consistent with antiferromagnetically- coupled chains. Reactions of CuCl2 center dot 2H(2)O with ligands 2 and 3 (2 = 4'-(3-pyridyl)-2,2':6',2 ''-terpyridine, 3 = 4'-(2-pyridyl)-2,2':6',2 ''-terpyridine) lead to monomeric complexes. With the exception of [Cu(3)Cl-2], the mononuclear complexes show a propensity for the incorporation of water into their crystal lattices; in the case of [Cu(H1)Cl-2]Cl center dot 4H(2)O and [Cu(H1)Cl-2]Cl center dot 4.75H(2)O, the small change in water content leads to the assembly of (5.8(2))(2)(5.6.8)(4)(5(2).6)(2) or (4(2).6(2))(3)(4.6(2))(6) water-chloride ion nets
Reversibly Tuning the Viscosity of Peptide-Based Solutions Using Visible Light
No full textLight can be used to design stimuli–responsive systems. We induce transient changes in the assembly of a low molecular weight gelator solution using a merocyanine photoacid. Through our approach, reversible viscosity changes can be achieved via irradiation, delivering systems where flow can be controlled non-invasively on demand.</p
Metal Template Synthesis of Molecular Knots and Links
Full text linkThe use of metal ions as templates to direct the assembly of complex architectures and topologies is briefly reviewed, highlighting milestones in the field from [2]catenanes, through to trefoil knots, Solomon links, Borromean rings and most recently to a molecular pentafoil knot
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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 Bridge Too Far: Testing the Limits of Polypyridyl Ligands in Bridging Soluble Subunits of a Coordination Polymer
No full textStarting with a coordination polymer, {[Cu(L)]2}n (1 where H2L = salicylidene-2-aminophenol), we have explored the ability of polypyridyl ligands (P) to bridge the monomer complex to form nine {[Cu(L)]2(P)} complexes. The identity and solution stability of the [Cu(L)] units has been investigated through a novel combined UV–vis/EPR experiment and it has been found to be a stable supramolecular building unit for the construction of discrete complexes and coordination polymers. The reorganization of [Cu(L)] units to a new coordination polymer on addition of 4,4′-bipyridine markedly changes the connectivity of the structure and the magnitude of the antiferromagnetic interactions through reorientation of the Cu(II) orbitals. We also present the structure of 1, 80 years after its synthesis was first reported
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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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