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991.
Dr. Daniele Del Giudice Dr. Francesco Tavani Dr. Marika Di Berto Mancini Dr. Federico Frateloreto Dr. Matteo Busato Dr. Danilo Oliveira De Souza Dr. Flavia Cenesi Prof. Osvaldo Lanzalunga Prof. Stefano Di Stefano Prof. Paola D'Angelo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(4):e202103825
The satisfactory rationalization of complex reactive pathways in solution chemistry may greatly benefit from the combined use of advanced experimental and theoretical complementary methods of analysis. In this work, we combine X-Ray Absorption and 1H NMR spectroscopies with state-of-the-art Multivariate Curve Resolution and theoretical analyses to gain a comprehensive view on a prototypical reaction involving the variation of the oxidation state and local structure environment of a selected metal ion coordinated by organic ligands. Specifically, we investigate the 2-cyano-2-phenylpropanoic acid reduction of the octahedral complex established by the Cu2+ ion with terpyridine to the tetrahedral complex formed by Cu+ and neocuproine. Through our interdisciplinary approach we gain insights into the nature, concentration time evolution and structures of the key metal (XAS measurements) and organic (1H NMR measurements) species under reaction. We believe our method may prove to be useful in the toolbox necessary to understand the mechanisms of reactive processes of interest in solution. 相似文献
992.
Daniele Del Giudice Matteo Valentini Gabriele Melchiorre Emanuele Spatola Prof. Stefano Di Stefano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(26):e202200685
This work reports that the composition of a dynamic library (DL) of interconverting imines can be controlled over time in a dissipative fashion by the addition of an activated carboxylic acid used as a chemical fuel. When the fuel is added to the DL, which is initially under thermodynamic equilibrium, the composition of the mixture dramatically changes and a new, dissipative (out of equilibrium) state is reached that persists until fuel exhaustion. Thus, a transient dissipative dynamic library (DDL) is generated that, eventually, reverts back to the initial DL when the fuel is consumed, closing a DL→DDL→DL cycle. The larger the amount of added fuel, the longer the time spent by the system in the DDL state. The transimination reaction is shown to be an optimal candidate for the realization of a dissipative dynamic covalent chemistry (DDCvC). 相似文献
993.
Fabricio Bublitz Melina de Azevedo Mello Daniele Cocco Durigon Felipe Dornelles da Silva Artur Luis Hennemann Ernesto Schulz Lang 《无机化学与普通化学杂志》2019,645(5):544-550
In this paper we explore an amino functionalized selenolate unit for the synthesis of new multinuclear compounds with promising interesting properties and potential precursors of semiconductors. We present for the first time the X‐ray crystallographic structure of [Hg(SeC6H4NH2)2]2 · diox ( 1· diox) and its copper(I) derivatives: HgCu2X2(SeC6H4NH2)2(PPh3)4 · 4diox [X = Br ( 2· 4diox) and I ( 3· 4diox)]. The compounds 1 and 2 , 3 can be considered as the starting material and intermediates, respectively, for the synthesis of ternary HgII/Se/CuI nanoclusters. We also provide IR and NMR spectroscopic data and evaluate the optical features of these compounds by difuse reflectance UV/Vis spectroscopy. 相似文献
994.
Chiara Biagini Giorgio Capocasa Valerio Cataldi Daniele Del Giudice Prof. Luigi Mandolini Prof. Stefano Di Stefano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(66):15205-15211
This work aimed to render phenomenologically autonomous the otherwise stepwise operation of a catenane-based molecular switch, which is chemically triggered by the decarboxylation of 2-cyano-2-phenylpropanoic acid ( 2 ). Given that any amount of 2 in stoichiometric excess with respect to the catenane is consumed in a side reaction, the authors resorted to the corresponding anhydride 5 , the slow hydrolysis of which, due to adventitious water in dichloromethane, continuously produces in situ the actual fuel 2 . As a consequence, the machine does not require a reloading after each cycle, but switches back and forth as long as fuel is present. 相似文献
995.
The efficient enzyme-catalyzed coupling of the indolic alkaloids catharanthine and vindoline was carried out by exploiting the oxidoreductases laccases and atmospheric oxygen. Following NaBH4 reduction of the eniminium cationic intermediate, the synthetically useful dimer anhydrovinblastine (AVBL) was isolated and characterized. Several reaction parameters were investigated in detail and, under the optimized reaction conditions, AVBL was isolated in 56% yield. The practicability of this bioconversion was further confirmed through the condensation of catharanthine with the vindoline analogue 11-methoxy-dihydrotabersonine. 相似文献
996.
997.
Alexei Gapeev Alberto Berton Daniele Fabris 《Journal of the American Society for Mass Spectrometry》2009,20(7):1334-1341
The hypothesis that direct determination of electrospray current would provide a viable method for maintaining spray stability
to enable optimal nanospray analysis was tested by building a feedback apparatus capable of reading the current and readjusting
the emitter voltage in real time. The apparatus consists of a current-sensing circuit that reads the voltage drop across a
resistor located between the high-voltage power supply and the nanospray emitter. A low voltage proportional to the observed
current is generated and sent to a data acquisition card. The information is used by a proportional-derivative-integral (PID)
algorithm to calculate the magnitude of a low-voltage signal that is used to control the power supply output. Any variation
of current across the sensing resistor is thus counteracted by an opposite-direction variation of the high voltage applied
to the nanospray emitter. In this way, the apparatus adjusts the emitter voltage to achieve a preset value of current, which
it strives to maintain over time in spite of any possible variation of the parameters influencing the spray regime. Preliminary
results have shown that the feedback apparatus is capable of establishing and maintaining stable spray for samples that are
usually considered challenging in traditional voltage-controlled analysis, such as those consisting of nucleic acid solutions
with high salt loads. For these types of samples, the total ion count recorded in current-controlled mode was significantly
more stable than that observed in voltage-controlled mode. At the same time, overall signal intensities and signal-to-noise
ratios were also significantly improved. Setting the target nanospray current to a predefined value and letting the apparatus
reach the target without operator intervention enabled the acquisition of viable data from solutions containing up to 2. 5
M ammonium acetate, which are ordinarily difficult by traditional manual tuning. A deeper understanding of the current-voltage
relationships for samples of very different compositions is expected to enable one not only to predict the target current
that should be used for a certain analysis, but also to devise algorithms to change such target as a function of predictable
variations of sample properties and analytical conditions. This will allow for optimal performance to be maintained during
on-line gradient chromatography in which the nature of the sprayed solution may vary very widely during the course of the
analysis. 相似文献
998.
We present some reoptimization techniques for computing (shortest) hyperpath weights in a directed hypergraph. These techniques are exploited to improve the worst-case computational complexity (as well as the practical performance) of an algorithm finding the K shortest hyperpaths in acyclic hypergraphs. 相似文献
999.
Daniele Faccio Miguel Angel Porras Gintaras Tamošauskas Arnaud Couairon 《Optics Communications》2006,265(2):672-677
We report measurements of ultrashort optical pulse filamentation in Kerr media with normal dispersion. We measure the angular dispersion of spontaneously generated colored conical emission and show that for large frequency shifts from the input pump frequency, it is well described by a relation between angle and frequency with slope determined solely by material chromatic dispersion. This measurement is in agreement with recent models that interpret filamentation dynamics in terms of the spontaneous formation of nonlinear X-waves. Finally, experimental results of filamentation in air show, for the first time, that the interpretation of CE in terms of X-waves may be also extended to gaseous media. 相似文献