1,721,192 research outputs found
Spectroscopic, EPR, X-ray structural, and DFT studies of the complex compound of N<sub>4</sub>-donor ligand with copper(II)
No full textA new mononuclear neutral five-coordinate copper(II) coordination compound [Cu(L)(H2O)] (1) (L = 6,6′-bis(NH-benzimidazol-2-yl)-2,2′-bipyridine) was synthesized and characterized by IR, UV–Vis, EPR and LC-MS (APCI) analysis. The crystal structure was also determined by X-ray crystallography. In 1, the copper(II) center adopts a five-coordinate distorted square-pyramidal (SP) geometry in which the basal plane formed by four of the nitrogen atoms of the ligand while the apical position is occupied by the oxygen atom of the water molecule. The four Cu–N bond lengths are 1.987(4), 1.992(4), 2.020(5) and 2.027(4) Å, and the longest bond of the apical Cu−Ow is 2.234(4) Å. The ligand undergoes deprotonation upon coordination to the metal center and acts as a dianionic tetradentate chelate to form a neutral complex [CuN4O]. The X-band EPR data of 1 are in agreement with the crystallographic data indicating a typical five-coordinate SP geometry. This geometry is also obtained by Density Functional Theory calculations. Time-dependent (TD) DFT calculations were used to shed light on the assignment and the nature of the electronic transitions observed in the UV–Vis spectrum. The calculated results are found to be consistent with the experimental data. Non-linear optical properties were also calculated by DFT calculations
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
Spectroscopic and structural studies of 6-(1-methylbenzimidazol-2-yl)-1H-pyridin-2-one and of an unusual T4(2)7(2)6(2)7(2) water tape stabilized by the copper(II) coordination polymer
No full textThe solid-state structures of 6-(1-methylbenzimidazol-2-yl)-1H-pyridin-2-one (HL) and the copper(II) complex [Cu(L-)2(OH2)]·2H2O (1) are established by X-ray crystallography and also by means of physicochemical and spectroscopic methods. The molecules of HL form a self-complementary head-to-tail hydrogen-bonded dimer through C-H ··· N and C-H ··· O contacts to give an infinite 1D chain. The copper( II) complex (1) is five-coordinate with distorted trigonal-bipyramidal (TBP) geometry of the N4O donor atoms. The electronic and EPR data are in agreement with the X-ray structure of 1, showing that HL coordinates to copper(II) centre as a mono-anionic ligand through deprotonated pyridone N atom and the tertiary benzimidazole nitrogen atom to form a neutral complex in which the water molecule occupies the fifth position. The 1D water tape, T4(2)7(2)6(2)7(2) is anchored to the host through hydrogen bonds between coordinated water molecule [O(3w)] as acting double H-donor, pyridone carbonyl groups [O(2) and O(1)] as double H-acceptor and the lattice water molecules [O(4w) and O(5w)] as double H-donor and single H-acceptor)
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
Spectroscopic, structural and DFT studies of luminescent Pt(II) and Ag(I) complexes with an asymmetric 2,2'-bipyridine chelating ligand
No full textA new unsymmetrically substituted 2,2′-bipyridine ligand, 5-methyl-5′-carbomethoxy-2,2′-bipyridine (L) was isolated from the dry distillation of the copper(II) complex, mono-aqua-bis(trans-5-methyl-pyridine-2-carboxylato-N,O)copper(II). The ligand was fully characterized. The spectroscopic and single-crystal X-ray diffraction (SCXRD) studies of the coordination compounds of the ligand with platinum(II) and silver(I); cis-Pt(L)Cl2 (1) and [Ag(L)2]PF6 (2), respectively are reported. In 1, the Pt centre coordinates to tertiary N atoms of the ligand and two chloride ions to form a neutral square-planar coordination sphere, while in 2, the Ag(I) centre is coordinated by two ligands through N atoms to generate a cationic flattened tetrahedron geometry in which two mean planes intersect each other at 50.93°. The pyridine rings are nearly coplanar as revealed by the torsion angle of N2-C7-C6-N1 1.32(5)°. In both complexes, L acts as a chelating ligand through pyridyl N atoms. In 1, the molecular units are stacked in a head-to-tail fashion with a Pt···Pt separation of 3.5 Å. Supramolecular self-assembly of the molecular units by extensive intermolecular contacts through C‒H···Cl and C‒H···O between the adjacent units results in an infinite two-dimensional flattened-out herringbone structure in the crystalline state. In 2, the molecular units are interconnected with each other by C‒H···O contacts between the adjacent units running parallel to each other. Both complexes are fluorescent in solution and have emission maxima in the UV-Vis regions, which is a very important property for optoelectronic applications. DFT (density functional theory) and TD-DFT (time-dependent-DFT) calculations were performed at B3LYP/6-311+G(d,p)/LANL2DZ level to explore structural, electronic, and spectroscopic properties to compare with the experimental results. The molecular orbitals (MOs) were carried out with DFT at the same level
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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