1,721,072 research outputs found
Raffaello Nasini: An Eclectic Chemist Heralding the Interdisciplinary Essence of Inorganic Chemistry
No full textThe Middle-Earth between Homogeneous and Heterogeneous Catalysis in Water Oxidation with Iridium
No full textInvited for the cover of this issue is Alceo Macchioni from University of Perugia, Italy. The cover image shows La Fontana Maggiore in Perugia. Its different water compartments symbolize the different types of iridium water oxidation catalysts reviewed in the article
Institute Feature: CIRCC Italy
No full textThe CIRCC, Interuniversity Consortium on Chemical Reactivity and Catalysis, includes 17 universities and over 75 research units in Italy, with the aim to develop new chemical reactions, new catalytic systems, and their possible industrial applications. This Guest Editorial presents the consortium to EurJIC readers and summarizes the scientific articles that are showcased in the Institute Feature dedicated to CIRCC
Optimizing noble metals exploitation in water oxidation catalysis by their incorporation in layered double hydroxides
No full textWater oxidation (WO) is considered the ideal process for the generation of electrons and protons necessary for the production of sustainable fuels. The unfavorable kinetics of this reaction requires the development of highly efficient catalysts (WOCs). The most promising performance has been obtained with noble metal based systems, which however pose challenges for the careful exploitation of these precious elements. In this Review, one of the most promising strategies for the development of WOCs in a ‘noble metal atom economy’ fashion is described, that is, the incorporation of these metals in layered double hydroxides (LDHs) of earth abundant elements. A rapidly raising number of studies demonstrate that excellent catalytic activity and durability can be obtained by following this strategy. The strong electronic coupling between noble metal nanoparticles or single atoms and the LDHs matrix is typically responsible for such intriguing results. Interestingly, noble metal incorporation as low as 1 wt% allows to boost the catalytic performance of intrinsically active systems like NiFe-LDHs, but also to activate otherwise inert materials like ZnAl-LDHs
Hemi-metallocene Ti(IV) η3-allyl-type complexes: Structure, dynamics in solution and exploration of reactivity
No full textThe cationic complexes [Cp*(tBu3P=N)Ti(η3-CH2C(C5H11)CH2)]+ (Ti-Alla+) and [Cp*(tBu3P=N)Ti(η3-CH2C(CH3)CH(C4H9))]+ (Ti-Allb+), bearing η3-allyl-type fragments coordinated to a Ti(IV) center with Cp* and phosphinimide ancillary ligands, were easily synthesized from the corresponding cationic Ti-benzyl complex by reaction with 2-methyl-1-heptene. The unusual stability of these allyl species at room temperature allowed detailed NMR spectroscopic investigation of their structure and dynamic behavior in solution. The spectroscopic results provided supporting experimental evidence for η3-coordination mode of the allyls and allowed to determine their preferential configuration. Furthermore, quantitative analysis of the exchange kinetics between syn and anti allylic protons was carried out by 1H EXSY NMR spectroscopy. The activation parameters for the latter process indicate that the faster exchange observed with Ti-Alla+ (ΔH‡ ≈ 16 kcal mol−1; ΔS‡ ≈ 0 cal mol−1 K−1) compared to Ti-Allb+ (ΔH‡ ≈ 11 kcal mol−1; ΔS‡ ≈ −19 cal mol−1 K−1) is primarily of entropic origin. A tentative interpretation for the higher stability of Ti-Alla+ and Ti-Allb+, compared to their bis-Cp titanocene analogues reported in the literature, is proposed based on steric considerations. Finally, an exploratory reaction, using benzaldehyde as representative substrate, was carried out to demonstrate the capability of Ti-Alla+ and Ti-Allb+ to serve as allylating agents for carbonyl compounds
From Atactic to Isotactic CO/p-Methylstyrene Copolymer by Proper Modifications of Pd(II) Catalysts Bearing Achiral alpha-Diimines
No full textCationic Pd(II) complexes modified with achiral C2v-symmetric α-diimine ligands allow preparation of atactic or isotactic stereoblock CO/p-methylstyrene copolymers; both catalyst activity and polyketone microstructure depend on the choice of α-diimine substituents and counterion
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
Extraction of Reliable Molecular Information from Diffusion NMR Spectroscopy: Hydrodynamic Volume or Molecular Mass?
No full textMeasuring accurate translational self-diffusion coefficients (D-t) by NMR techniques with modern spectrometers has become rather routine. In contrast, the derivation of reliable molecular information therefrom still remains a nontrivial task. In this paper, two established approaches to estimating molecular size in terms of hydrodynamic volume (V-H) or molecular weight (M) are compared. Ad hoc designed experiments allowed the critical aspects of their application to be explored by translating relatively complex theoretical principles into practical take-home messages. For instance, comparing the D-t values of three isosteric Cp2MCl2 complexes (Cp=cyclopentadienyl, M=Ti, Zr, Hf), having significantly different molecular mass, provided an empirical demonstration that V-H is the critical molecular property affecting D-t. This central concept served to clarify the assumptions behind the derivation of D-t=integral(M) power laws from the Stokes-Einstein equation. Some pitfalls in establishing log (D-t) versus log (M) linear correlations for a set of species have been highlighted by further investigations of selected examples. The effectiveness of the Stokes-Einstein equation itself in describing the aggregation or polymerization of differently shaped species has been explored by comparing, for example, a ball-shaped silsesquioxane cage with its cigar-like dimeric form, or styrene with polystyrene macromolecules
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