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931.
Marina Massaro Carmelo G. Colletti Bruno Fiore Valeria La Parola Giuseppe Lazzara Susanna Guernelli Nelsi Zaccheroni Serena Riela 《应用有机金属化学》2019,33(3)
A highly sustainable prototype of a flow system based on gold nanoparticles (4.2 nm) supported on thiol‐functionalized halloysite nanotubes (HNTs) was developed for catalytic applications. The catalytic performances were evaluated using the reduction of 4‐nitrophenol to 4‐aminophenol as a model system. Under the best experimental conditions (0.0001 mol%, 1.97 × 10?8 mg of Au nanoparticles), an impressive apparent turnover frequency value up to 2 204 530 h?1 was achieved and the halloysite‐based catalyst showed full recyclability even after ten cycles. The high catalytic activity confirms the importance of the use of HNTs as support for Au nanoparticles that can exert a synergistic effect both as medium for transfer of electrons from borohydride ions to 4‐nitrophenol and by modulating interfacial electron transfer dynamics. With the application of flow technology, the obtained heterogeneous HNT@Au catalyst was fully recovered and reused for at least one month. 相似文献
932.
Dr. Luis M. Mateo Luca Sagresti Dr. Yusen Luo Prof. Dirk M. Guldi Prof. Tomas Torres Dr. Giuseppe Brancato Dr. Giovanni Bottari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(64):16049-16055
Tetracyanobuta-1,3-diene (TCBD) is a powerful and versatile electron-acceptor moiety widely used for the preparation of electroactive conjugates. While many reports addressing its electron-accepting capability have appeared in the literature, significantly scarcer are those dealing with its chemical modification, a relevant topic which allows to broaden the chemical space of this interesting functional unit. Here, we report on the first example of a high-yielding cyano-Diels-Alder (CDA) reaction between TCBD, that is, where a nitrile group acts as a dienophile, and an anthryl moiety, that is, acting as a diene. The resulting anthryl-fused-TCBD derivative, which structure was unambiguously identified by X-ray diffraction, shows high thermal stability, remarkable electron-accepting capability, and interesting electronic ground- and excited-state features, as characterized by a thorough theoretical, electrochemical, and photophysical investigation. Moreover, a detailed kinetic analysis of the intramolecular CDA reaction transforming the anthryl-TCBD-based reactant into the anthryl-fused-TCBD product was carried out at different temperatures. 相似文献
933.
Giuseppe Ancona 《manuscripta mathematica》2015,146(3-4):307-328
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We investigate inner shearing constraints for a direct one-dimensional beam model coarsely describing warping. In particular, we study how they affect the field equations for the elastic buckling of open thin-walled beams. We show that the distinction between the axes of the shear centres and of the centroids is crucial for the kinematics of the beam, and to derive expression of reactive actions, hence of buckling critical conditions. We also show how a suitable definition of the warping inertial action and properly introduced inner shearing constraints yield the field equations of the literature for the beam in a general dynamic setting. 相似文献
938.
Gabriella Butera Claudio De Pasquale Antonella Maccotta Giuseppe Alonzo Pellegrino Conte 《Cellulose (London, England)》2011,18(6):1499-1507
Use of crude oil derivatives such as diesel and gasoline is becoming unsuitable due to their detriment to environment and
to the increasing worldwide energy demand which is driving crude oil reservoirs towards exhaustion. Replacement of diesel
and gasoline with biofuels (i.e. biodiesel and bioethanol, respectively) is very desirable. In fact, biofuels are not only
environmentally sustainable, but also potentially inexhaustible due to the large amounts of waste biomasses from which they
can be retrieved. In the present study, a model compound (micro-crystalline cellulose) was dissolved in phosphoric acid and
converted at 80 °C to glucose, thereby providing the possible substrate for fermentation to bioethanol. Results revealed that
after 1 h heating, the reaction had the largest glucose yield as compared to similar studies done by using other acid catalysts.
In addition, the temperature applied here was from 40 to 60 °C lower than those already reported in literature for acid-driven
cellulose degradations. Phosphoric acid allowed both glucose and levulinic acid achievement. The latter is usually used to
synthesize fuel additives, catalysts, solvents and herbicides, thereby enhancing the added value of the conversion of cellulose
to glucose in phosphoric acid. Finally, 1H T1 NMR relaxometry showed its suitability to monitor cellulose degradation. The advantages of relaxomety are its quickness since
only few minutes are needed to obtain relaxograms, and the possibility to use raw mixtures without the needing of sample preparation. 相似文献
939.
Dr. Amit Kumar Sarnali Sanfui Dr. Giuseppe Sciortino Prof. Jean-Didier Maréchal Prof. Eugenio Garribba Prof. Sankar Prasad Rath 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(35):7869-7880
cis and trans-copper(II) porphyrin dimers have been synthesized, in which two CuII porphyrin macrocycles are bridged through a rigid ethene linker for possible through-space and through-bond spin-couplings between the paramagnetic CuII centers. It has been found that the two macrocycles come closer after 1 e− oxidation, however, they move far apart upon further 1 e− oxidation leading to transformation of the cis to the trans isomer. Detailed investigations are performed here on the interactions between the two porphyrin macrocycles, between two unpaired spins of closely spaced CuII centers, and also between the unpaired spins of metal and porphyrin π–cation radicals. Spectroscopic investigations along with the X-ray structure of the 2 e−-oxidized complex displayed strong electronic communications through the bridge between two porphyrin π–cation radicals. The counterion I9− is stabilized in an unusual trigonal-pyramidal structure in the 2 e−-oxidized complex in which the central iodide ion is bound with four iodine (I2) molecules. Variable-temperature magnetic study revealed strong antiferromagnetic coupling between the two porphyrin π–cation radical spins (Jr–r) in the 2 e−-oxidized complex. DFT calculations suggest stabilization of the triplet state, which is also in good agreement with the experiment. Ab initio molecular dynamics allowed the variation of the structural details to be followed upon stepwise oxidations and also the final isomerization process including its associated energy barrier. 相似文献
940.
Dr. Daniele Maiolo Dr. Andrea Pizzi Dr. Alessandro Gori Dr. Lara Gazzera Dr. Nicola Demitri Dr. Alessandro Genoni Dr. Fulvio Baggi Dr. Fabio Moda Prof. Dr. Giancarlo Terraneo Prof. Dr. Francesca Baldelli Bombelli Prof. Dr. Pierangelo Metrangolo Prof. Dr. Giuseppe Resnati 《ChemistryOpen》2020,9(2):253-260
Here, we demonstrate that introduction of halogen atoms at the tyrosine 10 phenol ring of the DSGYEV sequence derived from the flexible amyloid-β N-terminus, promotes its self-assembly in the solid state. In particular, we report the crystal structures of two halogen-modified sequences, which we found to be stabilized in the solid state by halogen-mediated interactions. The structural study is corroborated by Non-Covalent Interaction (NCI) analysis. Our results prove that selective halogenation of an amino acid enhances the supramolecular organization of otherwise unstructured biologically-relevant sequences. This method may develop as a general strategy for stabilizing highly polymorphic peptide regions. 相似文献