1,720,984 research outputs found
1,10-Phenanthroline-5,6-dione as a building block for the synthesis of homo- and heterometallic complexes
No full text1,10-Phenanthroline-5,6-dione (C12H6N2O2 (1)) reacts with V(6-mesitylene)2 and Ti(6-toluene)2 affording coordination
compounds of general formula M(O,OC12H6N2O2)3 (M=Ti (2); M=V (3)) which further react with TiCl4 or TiCp2(CO)2
yielding the tetrametallic species M(O,OC12H6N2O2N,N)3(MLn)3 (M=V, MLn=TiCl4 (4); M=Ti, MLn=TiCp2 (5);
M=V, MLn=TiCp2 (6)). The complex salt [Fe(N,NC12H6N2O2)3][PF6]2 (7) has been obtained from iron(II) chloride
tetrahydrate and 1 in the presence of NH4PF6. The reaction of 7 with TiCp2(CO)2 affords the tetrametallic derivative
[Fe(N,NC12H6N2O2O,O)3(TiCp2)3][PF6]2 (8). TiCl2(THF)2 reacts with MCp2(O,OC12H6N2O2) to give
MCp2(O,OC12H6N2O2N,N)TiCl2 (M=Ti (9); M=V (10)). By reaction of TiCp2(O,OC12H6N2O2N,N)TiCl2 (9) with
C12H6N2O2, the bimetallic derivative TiCp2(O,OC12H6N2O2N,N)TiCl2(O,OC12H6N2O2) (11) has been prepared, which
readily adds to TiCl4, to give the trimetallic titanium derivative TiCp2(O,OC12H6N2O2N,N)TiCl2(O,OC12H6N2-
O2N,N)TiCl4 (12). VCp2(O,OC12H6N2O2N,N)TiCl2 (10) reacts with the tris-chelate iron(II) cation 7 affording the heptametallic
cationic complex [Fe(N,NC12H6N2O2O,O)TiCl2(N,NC12H6N2O2O,O)VCp2]3
+2 isolated as the hexafluorophosphate
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Coordination properties of 1,10-phenanthroline-5,6-dione towards Group 4 and Group 5 metals in low- and high oxidation states
No full textThe molecular structure of 1,10-phenanthroline-5,6-dione has been determined by X-ray diffraction analysis. The
compound reacts with the tetrachlorides of Group 4 metals affording adducts of general formula [MCl4(C12H6N2O2)]
(M = Ti, Zr or Hf) and [(MCl4)2(C12H6N2O2)] (M = Ti or Hf), N,N- and N,N,O,O-co-ordinated respectively. The
compound [HfCl4(C12H6N2O2)] is reactive towards TiCl4 affording the bimetallic compound [Cl4Hf(C12H6N2O2)-
TiCl4]. The reaction of the dione with bis-cyclopentadienyl derivatives of titanium(), zirconium(), [MCp2(CO)2],
and vanadium(), VCp2, affords derivatives O,O-co-ordinated to the MCp2 moiety. By reaction of [TiCp2-
(C12H6N2O2)] with [TiCp2(CO)2] the bimetallic derivative [(TiCp2)2(C12H6N2O2)] is obtained, which is suggested
to contain two TiCp2 fragments, O,O- and N,N-co-ordinated to 1,10-phenanthroline-5,6-dione. The [MCp2-
(C12H6N2O2)] (M = Ti, Zr or V) derivatives react with MCl4 (M = Ti or Hf) to give [Cp2M(C12H6N2O2)MCl4]
bimetallics
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
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
Inside the small length and energy scales of the world of the individual biological molecules.
No full textAtomic force microscopy (AFM) has proved to be an essential tool of structural biology, being able not only to image but also to manipulate single biological molecules. These techniques make it possible to investigate the nanometer scale structure of single biological macromolecules and to study how an external force drives single biological molecules towards non-equilibrium conformations, by stretching and breaking bonds and interactions. This chapter focuses on the capabilities of the AFM-based single molecule methodologies to bring us into the nanometer-scale world of the single DNA molecules and into the pico-Newton force-scales of the interactions that sustain the protein folding
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
Synthesis and characterization of mono and bimetallic derivatives of Groups 4 and 5 with 2,5dimethoxy1,4benzoquinone
No full textThe ligating properties of 2,5-dimethoxy-1,4-benzoquinone, C8H8O4 1 towards metallic Lewis acids and organometallics
in low oxidation states has been investigated. The title compound reacts with Group 4 tetrahalides to give adducts of
formula MCl4(C8H8O4) (M = Ti 4a; M = Zr 4b) and (TiCl4)2(C8H8O4) 5. Moreover, bis-cyclopentadienyl derivatives of
titanium() (TiCp2L2; L = CO, PMe3) and vanadium() (VCp2) react with 1 affording both 1 : 1 and 2 : 1 derivatives
of general formula MCp2(C8H8O4) (M = Ti 10; M = V 7), (MCp2)2(C8H8O4) (M = Ti 11; M = V 6). The molecular
structure of 6 has been determined by X-ray diffraction showing the presence of bimetallic units, with two [VCp2]
fragments bonded to a quinonoid oxygen atom of a bridging 2,5-dimethoxy-1,4-benzenedialcoholato. The derivatives
[(MCp2)2(C8H8O4)][BPh4]n (M = Ti, V; n = 1 12a, b; n = 2 12c, d) have been prepared by oxidation of (MCp2)2(C8H8O4)
(M = Ti 11; M = V 6) with a stoichiometric amount of [FeCp2][BPh4]. The reaction of the vanadium derivative
VCp2(C8H8O4) 7 with TiCl4 affords the heterobimetallic compound VCp2(C8H8O4)TiCl4 8. The magnetic properties
of the 1 : 1 and 2 : 1 species are reported
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