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A theoretical study of the occupied and unoccupied electronic structure of high-and intermediate-spin transition metal phthalocyaninato (Pc) complexes: VPc, CrPc, MnPc, and FePc
Full text linkThe structural, electronic, and spectroscopic properties of high-and intermediate-spin transition metal phthalocyaninato complexes (MPc; M = V, Cr, Mn and Fe) have been theoretically investigated to look into the origin, symmetry and strength of the M–Pc bonding. DFT calculations coupled to the Ziegler’s extended transition state method and to an advanced charge density and bond order analysis allowed us to assess that the M–Pc bonding is dominated by σ interactions, with FePc having the strongest and most covalent M–Pc bond. According to experimental evidence, the lightest MPcs (VPc and CrPc) have a high-spin ground state (GS), while the MnPc and FePc GS spin is intermediate. Insights into the MPc unoccupied electronic structure have been gained by modelling M L2,3-edges X-ray absorption spectroscopy data from the literature through the exploitation of the current Density Functional Theory variant of the Restricted Open-Shell Configuration Interaction Singles (DFT/ROCIS) method. Besides the overall agreement between theory and experiment, the DFT/ROCIS results indicate that spectral features lying at the lowest excitation energies (EEs) are systematically generated by electronic states having the same GS spin multiplicity and involving M-based single electronic excitations; just as systematically, the L3-edge higher EE region of all the MPcs herein considered includes electronic states generated by metal-to-ligand-charge-transfer transitions involving the lowest-lying π* orbital (7eg) of the phthalocyaninato ligand
Interplay between local structure and supramolecular order in the reactivity of surface-supported molecular aggregates
No full textSPM tools have been extensively used in recent years to prepare, characterize and test the structural and functional properties of self-assembled molecular networks on surfaces. In many cases the molecular positional and conformational degrees of freedom determine a complex interfacial energy landscape, where subtle equilibria lead to the formation of various 2D ordered phases, often related to each other by phase transitions able to trigger the molecular reactivity, which therefore depends on subtle interrelations between local adsorption sites, intramolecular structure and long range supramolecular order. This talk will address some aspects of the structure-reactivity relationships in several surface-supported molecular networks, studied by means of STM complemented by other surface science and computational tools: e.g. the dependence of the catalytic activity toward oxygen reduction and of the magnetic properties of an Ag-supported iron phthalocyanine monolayer on the supramolecular arrangement of the molecules [1]; the requirements for either thermal [2] or photo-excited [3] covalent stabilization of single- and bicomponent supramolecular networks containing functionalized porphyrins on Ag low-index surfaces; the bottom up synthesis of long range ordered 1D poly-para-phenylene nanowires and 2D graphene nanoribbons on gold substrates [4]. [1] Casarin et al., J. Phys. Chem. C, 2010 ,114, 2144; Sedona, F. et al. Nat. Mater, 2012, 11, 970, Bartolomé et al. J. Phys. Chem. C, 2015 ,119, 12488. [2] Di Marino et al., Langmuir, 2010, 26, 2466; Sedona et al., ACS Nano, 2010, 4, 5147; Sedona et al. J. Phys. Chem. C, 2014 ,118, 1587. [3] Basagni et al., Chem. Eur. J. 2014, 20, 14296. [4] Basagni et al., J. Am. Chem. Soc. 2015, 137, 1802; Basagni et al., ACS Nano 2016, 10, 2644
On-surface Photochemistry of Pre-ordered 1-Methyl-2-phenyl-acetylenes: C-H Bond Activation and Intermolecular Coupling on Highly Oriented Pyrolytic Graphite
Full text linkIn thiscontributionwereporton light-inducedmetal-freecouplingof propynylbenzenemolecularunitsonhighlyorientedpyrolyticgraphite.The reactionoccurswithinthe self-assembledmonolayerandleadsto the generationof covalentlycoupled1,5-hexadiyneandpara terphenylderivativesundertopologicalcontrol. Such photochemical uncatalysed pathway represents an original approachin the fieldof topological C-C coupling at the solid/liquid interface and provides new insight into the low temperature formation of aromatic compounds at the surface of carbonaceous supports
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
Erratum: Characterization and Modeling of Reduced-Graphene Oxide Ambipolar Thin-Film Transistors (IEEE Transactions on Electron Devices (2022) 69:6 (3192-3198) DOI: 10.1109/TED.2022.3169451)
No full textIN THE above article [1], an error is present in (1). The correct equation should read as in (1), shown at the bottom of the page. This is the equation that was used to extrapolate the fitting parameters reported in Table II and to draw the fitting curve reported in Fig. 6. Therefore, the scientific results and conclusions in the original manuscript do not change. (Figure Presented)
The role of acetonitrile in the direct synthesis of hydrogen peroxide over palladium supported by ion-exchange resins
Full text linkAcetonitrile is used as an effective, non-corrosive selectivity enhancer for the direct synthesis of hydrogen peroxide (HP). Palladium catalysts supported by activated carbon or poly-divinylbenzene are poisoned by acetonitrile, which makes them very little productive. Conversely the catalysts supported by strongly acidic ion-exchange resin are much more selective and productive in the presence of acetonitrile, and for relatively long time. TEM shows that the size of their metal nanoparticles can be decreased by a reconstruction process, possibly sustained by leached palladium(II) species. HP decomposition experiments show that acetonitrile inhibits the O-O bonds splitting
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