1,720,963 research outputs found
remediation.
No full textIn this Perspective article, recent developments in the self-assembly of supramolecular porous materials made of zero-dimensional (0D) porous metal organic cages (MOCs), connected by different approaches, and their application in CO2 remediation are reviewed. The connection of MOCs carried out by coordination-bond driven linking, covalent bond linking and mechanical bond formation, leads to the formation of novel smart materials ranging from solid to gel states of matter, and in some cases, porous materials with hierarchical porosity stemming from the intrinsic MOC porosity and the voids generated among the connected MOCs. Both porosities can be tuned depending on the MOC sizes and on the way the cages are connected (i.e., coordination-driven and covalent bond linking). In general, the supramolecular, often networked, materials arising from the connection of MOCs tend to show diffuse scattering, denoting only short-range order, making their structural elucidation very challenging or simply not possible. Thus, the bulk structure of materials formed by connected MOCs is often deduced from information obtained through other techniques like powder XRD, pair distribution function (PDF) analysis, solid-state NMR, dynamic light scattering (DLS), and positron annihilation lifetime spectroscopy (PALS). Materials obtained upon the connection of MOCs are usually in the form of amorphous solids, gels, xerogels and porous liquids (PLs) but have shown to outperform the CO2 capacity and improved mechanical properties when compared to the single MOCs. The preparation of materials at the interface between solids and liquids is important to create functional materials displaying unique properties such as porosity in liquids and gels arising from the MOCs and their networked assembly, hence allowing CO2 gas diffusion into the cage's voids where CO2 can be trapped or catalytically transformed into other molecules (i.e., formic acid (HCOOH)). Thus, materials containing connected MOCs can be exploited where MOFs cannot be used due to their brittle nature, typical of solid crystalline materials, for instance in applications where the porous material has to fit to different shapes for example those required to fit in tubes or shapes that usually crystalline solids cannot adapt easily, thus expanding the applications of connected MOC materials in areas involving fluids
Transition Metal Complexes with Azahelicene: Synthesis and Characterization
No full textAzahelicenes have attracted great interest for their unique structural properties that make them
promising materials for applications in optoelectronics, catalysis, sensors and more. Transition metal
complexes of azahelicenes are interesting for the strong UV absorbance of helicenes and the
possibility of energy transfer to the metal ion. Some transition metal complexes of aza[5]helicene
have been synthesized and characterized. This communications reports on the synthetic patway,
multinuclear NMR characterization and single crystal X-ray structure of some representative term
ChemInform Abstract: Second Sphere Coordination of Hybrid Metal‐Organic Materials: Solid State Reactivity
No full text
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
Ab Initio Powder X-Ray Diffraction Structural Analysis of Bispidine Based 1D Coordination Polymer: Insight into their Guest Responsive Behaviour
No full textThe first ab initio synchrotron powder X-ray diffraction (XRD) data structure solution, employing real-space global optimization strategies followed by Rietveld refinement, was obtained for a bispidine based one-dimensional ribbon-like coordination polymer (CP) 1. The structure solution of 1, a non-dynamic phase containing no solvent molecules, is crucial to obtain a more comprehensive view of the dynamic behaviour of a new family of 1D CPs, in terms of solvent adsorption and exchange processes by direct comparison among the structures, solvent–ribbon and inter-ribbon interactions of the CP materials. This work also reports novel bisolvated phases, 1·TCM·oNT, 1·TCM·pCT and 1·TCM·NB, in the form of single crystals and microcrystalline powders and shows that 1 can be thermally activated to regain dynamic selective adsorption features
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
Synthesis and structural properties of isostructural Zn(II) M12L8 poly-[n]-catenane using the 2,4,6-tris(4-pyridyl)benzene (TPB) ligand
Full text linkThe use of mechanical bonds for the synthesis of catenanes is a challenging process because of the many factors controlling the
interpenetration process.[1,2] We report the kinetic control in the presence of various aromatic solvents of a poly-[n]-catenane (1).
The polymeric structure is composed of interlocked M12L8 icosahedral nanometric cages with internal voids of ca. 2500 Å3.[3] Using
the symmetric exotridentate tris-pyridyl benzene (TPB) ligand and ZnCl2 with appropriate templating solvent molecules due to the
good ligand aromatic interactions are used, the metal-organic nanocages can be synthesized very fast, homogeneously, and in large
amounts as microcrystals (Figure 1). Synchrotron single-crystal X-ray data (100 K) allowed the resolution of nitrobenzene guest
molecules at the internal walls of the M12L8 cages, while in the centre of the nanocages the solvent is disordered and not observable by
X-ray diffraction data. The guest release occurs in two steps with the disordered nitrobenzene released in the first step (lower
temperatures) because of the lack of strong cage-guest interactions. Solid-state quantum mechanics provided a rationalization of the
results, in particular, solid-state approaches, showed theoretical evidence of the kinetic nature in the formation of the polycatenation of
the M12L8 nanocages by the analysis of the packing energy considering monomeric and dimeric cages
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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