1,720,960 research outputs found
Benzothiazolin-2-ylidene gold(I) complexes as precursors for gold nanoparticles
Full text linkThe preparation of gold(I) complexes with benzothiazolin-2-ylidene ligands is described herein. These previously unreported complexes can be conveniently prepared from the corresponding benzothiazolium precursors using the so-called weak base route and have been spectroscopically and structurally characterized. Combined structural and computational analysis confirms enhanced π-accepting character of benzothiazolin-2-ylidine ligands in comparison with conventional (benz)imidazolin-based NHCs. The obtained complexes are reasonably stable and have been used as precursors for ligand-stabilized gold nanoparticles by controlled reduction with potassium hydride. The reaction produces 3 nm sized gold nanoparticles that are stable in solution as well as in the solid state and can be characterized both spectroscopically (NMR, UV–Vis) and by transmission electron microscopy (TEM)
Palladium(ii) complexes with electron-poor, 4,5-disubstituted diimidazol-2-ylidene ligands: Synthesis, characterization and catalytic activity
No full textDiimidazolium salts featuring different bridges between the imidazolium groups, as well as electron-withdrawing groups (chloride, cyanide) at the 4- and 5-position of the heterocyclic rings, have been successfully prepared. The diimidazolium salts serve as convenient precursors of di(N-heterocyclic carbene) ligands, which coordinate in a chelating fashion to palladium(II) centres. The effect of the newly introduced electron-withdrawing groups on the spectroscopic and structural characteristics of the resulting complexes as well as on their reactivity as catalysts in a model alkyne hydroarylation reaction has been investigated and is discussed herei
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
Bright luminescent lithium and magnesium carbene complexes
No full textWe report on the convenient synthesis of a CNC pincer ligand composed of carbazole and two mesoionic carbenes, as well as the corresponding lithium- and magnesium complexes. Mono-deprotonation affords a rare “naked” amide anion. In contrast to the proligand and its mono-deprotonated form, tri-deprotonated s-block complexes show bright luminescence, and their photophysical properties were therefore investigated by absorption- and luminescence spectroscopy. They reveal a quantum yield of 16% in solution at ambient temperature. Detailed quantum-chemical calculations assist in rationalizing the emissive properties based on an Intra-Ligand-Charge-Transfer (ILCT) between the carbazolido- and mesoionic carbene ligands. (Earth-)alkali metals prevent the distortion of the ligand following excitation and, thus, by avoiding non-radiative deactivation support bright luminescence
Correction: Aromaticity and sterics control whether a cationic olefin radical is resistant to disproportionation
No full textCorrection for ‘Aromaticity and sterics control whether a cationic olefin radical is resistant to disproportionation’ by Julian Messelberger et al. , Chem. Sci. , 2020, 11 , 4138–4149, DOI: 10.1039/D0SC00699H
Aromaticity and sterics control whether a cationic olefin radical is resistant to disproportionation
No full textVariations 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
- …
