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Structural characterization of bimetallic Pd-Cu vapor derived catalysts
Full text linkPd-Cu bimetallic Solvated Metal Atoms (SMA) were synthesized by metal vapor synthesis technique and supported on PVPy resin. Since the catalytic activity, of the Pd-Cu system turned out to be quite high also compared to the corresponding monometallic system, a structural characterization, using electron microscopy techniques and X-ray Absorption Fine Structure spectroscopy, was performed. HRTEM analysis showed the presence of Pd particles distributed in a narrow range with a mean diameter of about 2.5 nm while the XAFS analysis, confirmed the presence of the Pd nanoparticles but revealed also some alloying with Cu atoms
PALLADIUM NANOPARTICLES SUPPORTED ON MESOPOROUS SILICA: APPLICATIONS IN CONTINUOUS-FLOW MIZOROKI-HECK REACTIONS
No full textHerein we wish to report our recent results in the Mizoroki–Heck alkenylations under batch and continuous-flow ligandless conditions, by using Metal Vapour Synthesis (MVS) derived Pd nanoparticles deposited on mesoporous silica powder (MCM-41)
PALLADIUM NANOPARTICLES ON POLYVINYLPYRIDINE SUPPORTS: APPLICATIONS IN CONTINUOUS-FLOW MIZOROKI-HECK REACTIONS
No full textMetal vapor synthesis (MVS) technique provides a valuable synthetic route to obtain supported Pd nanoparticles featuring strictly controlled dimension (< 5 nm). These systems proved highly efficient catalysts in Mizoroki-Heck alkenylations of aryl halides (I, Br) with acrylates, to give the corresponding trans-cinnammates in high yields under batch reaction conditions.
Here we wish to report our recent results in continuous-flow Mizoroki-Heck alkenylations using MVS-derived Pd nanoparticles deposited on pyridine-based organic supports, both in the form of powder (PVPy) and as mesoporous organic monolith
Characterization of a Poly-4-Vinylpyridine-Supported CuPd Bimetallic Catalyst for Sonogashira Coupling Reactions
No full textCuPd bimetallic solvated metal atoms (SMA) synthesized by metal vapor synthesis (MVS) technique and supported on poly-4-vinylpyridine (PVPy) resin, showed significantly higher catalytic activity in Sonogashira-type carbonâcarbon coupling reactions than the corresponding monometallic Cu and Pd systems as well as their physical mixture. The analysis of the bimetallic catalyst combining transmission electron microscopy techniques and X-ray absorption fine structure (XAFS) spectroscopy revealed the presence of small Pd nanoparticles (dm=2.5 nm) while the analysis of the X-ray absorption data, at the Cu K-edge suggests the formation of thin and incomplete Cu oxide layers around the Pd-rich cores
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
Individuation and study of supported catalytic systems suitable for practically useful C-C cross-coupling reactions performed in batch and/or flow conditions
No full textIn the context of organic chemistry, and in particular in the C-C cross-coupling reactions catalyzed by transition metals such as nickel or palladium, the use of green and environmental friendly synthetic methodologies is of growing interest for both Academy and Industry. In this context, the replacement of homogeneous metal catalysts with heterogeneous systems and the replacement of classical batch-type reactors with continuous flow systems is today considered of primary importance.
Our investigations demonstrated that under rather simple and convenient conditions (a moderate excess of bases, a moderate amount of organic solvents, or in some cases, in only water or in absence of solvents, under aerobic atmosphere and with very low metals loading (0.10-0.15 mol% of Pd); cheap, simple, practical, easily available and industrially acceptable supported catalysts (“purpose-build” and/or commercial), and continuous-flow packed-bed systems, could be conveniently applied in C-C bond forming reactions of particular interest, such as Mizoroki-Heck alkenylations, Sonogashira-type alkynylations and Suzuki-Miyaura reactions; obtaining very good results.
Moreover, we reported the application of these systems in one the firstly synthesis of nataural and analogues bioactive compounds in batch and flow mode using supported catalysts
Synthesis of Pterostilbene through supported-catalyst promoted Mizoroki-Heck reaction, and its transposition in continuous flow reactor
Full text linkPterostilbene, an important polyphenolic compound with interesting biological activities, has been efficiently synthesized through a Mizoroki-Heck reaction catalyzed by commercially available Pd catalysts immobilized onto heterogeneous supports. The synthesis has been transposed in a continuous flow reactor, following two different retrosynthetic approaches. [Figure not available: see fulltext.]
Nanoparticolati di Pd supportati preparati via Metal Vapour Synthesis: il primo studio sulle possibilità di impiego in reazioni di Suzuki e tipo-Sonogashira
No full textLa catalisi eterogenea sta prendendo sempre più importanze nella ricerca sia accademica che industriale e, la preparazione di catalizzatori supportati "via" MVS si presenta come una tecnica con proprietà e caratteristiche molto interessanti (che si ritrovano sui catalizzatori così preparati), rispetto ai comuni sistemi di preparazione, oltre che ai singoli catalizzatori ottenuti. Pertanto appare molto interessante uno studio sulle possibilità di impiego di questi catalizzatori supportati preparati "via" MVS, non ancora mai stati studiati in reazioni di cross-coupling, e soprattutto nelle reazioni di più grande interesse quali la Suzuki e le alchinilazioni tipo-Sonogashira
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
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