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41.
Bimolecular Homolytic Substitutions at Nitrogen: An Experimental and Theoretical Study on the Gas‐Phase Reactions of Alkyl Radicals with NF3 下载免费PDF全文
Dr. Paola Antoniotti Dr. Paola Benzi Dr. Stefano Borocci Dr. Chiara Demaria Dr. Maria Giordani Prof. Felice Grandinetti Prof. Lorenza Operti Prof. Roberto Rabezzana 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15826-15834
The X‐ray irradiation of binary mixtures of alkyl iodides R?I (R=CH3, C2H5, or i‐C3H7 radicals) and NF3 produces R?NF2 and R?F. Based on calculations performed at the CCSD(T), MRCI(SD+Q), G3B3, and G3 levels of theory, the former product arises from a bimolecular homolytic substitution reaction (SH2) by the alkyl radicals R, which attack the N atom of NF3. This mechanism is consistent with the suppression of R?NF2 by addition of O2 (an efficient alkyl radical scavenger) to the reaction mixture. The R?F product arises from the attack of R to the F atom of NF3, but additional contributing channels are conceivably involved. The F‐atom abstraction is, indeed, considerably more exothermic than the SH2 reaction, but the involved energy barriers are comparable, and the two processes are comparably fast. 相似文献
42.
Operti L Rabezzana R Turco F Vaglio GA 《European journal of mass spectrometry (Chichester, England)》2007,13(6):377-384
The gas phase ion-molecule reactions in positively and negatively ionized germane/diborane mixtures have been studied by ion trap mass spectrometry. Reaction sequences and rate constants for the most interesting processes have been determined. In positive ionization, formation of Ge-B bonds exclusively occurs through condensation reactions of B(n)H(m)(+) ions with germane, followed by H(2) or BH(3) loss. No reactions of ions from germane with B(2)H(6) were observed under the experimental conditions used here. In negative ionization, the Ge(n)H(m)(-) (n = 1, 2) ion families react with diborane to yield the Ge(n)B(p)H(q)(-) (p = 1, 2) ions, again via dehydrogenation and BH(3) loss, while diborane anions proved to be unreactive. In both positive and negative ionization, Ge-B ions reach appreciable abundances. The present results afford fundamental information about the intrinsic reactivity of gas-phase ions and provide valuable indications about the first nucleation steps ultimately leading to amorphous Ge and B-doped semiconductor materials by chemical vapor deposition methods. 相似文献
43.
Petra Martini Alessandra Boschi Lorenza Marvelli Licia Uccelli Stefano Carli Giuseppe Cruciani Erika Marzola Anna Fantinati Juan Esposito Adriano Duatti 《Molecules (Basel, Switzerland)》2021,26(19)
(1) Background: Metal dithiocarbamate compounds have long been the subject of research due to their ease of formation, excellent properties and potential applications. However, manganese complexes with dithiocarbamates, to our knowledge, have never been used for medical imaging applications. With the aim of developing a new class of mononuclear manganese(II)-based agents for molecular imaging applications, we performed a specific investigation into the synthesis of mononuclear bis-substituted Mn(II) complexes with dithiocarbamate ligands. (2) Methods: Synthesis in either open or inert atmosphere at different Mn(II) to diethyldithiocarbamate molar ratios were performed and the products characterized by IR, EA, ESI-MS and XRD analysis. (3) Results: We found that only under oxygen-free atmospheric conditions the Mn(II) complex MnL2, where L = diethyldithiocarbamate ligand, is obtained, which was further observed to react with dioxygen in the solid state to form the intermediate superoxo Mn(III) complex [MnL2(η2-O2)]. The existence of the superoxo complex was revealed by mass spectroscopy, and this species was interpreted as an intermediate step in the reaction that led the bis-substituted Mn(II) complex, MnL2, to transform into the tris-substituted Mn(III) complex, MnL3. A similar result was found with the ligand L’ (= bis(N-ethoxyethyl)dithiocarbamate). (4) Conclusions: We found that in open atmosphere and in aqueous solution, only manganese(III) diethyldithiocarbamate complexes can be prepared. We report here a new example of a small-molecule Mn(II) complex that efficiently activates dioxygen in the solid state through the formation of an intermediate superoxide adduct. 相似文献
44.
Maurizio Delcanale Gabriele Amari Elisabetta Armani Milco Lipreri Maurizio Civelli Elisabetta Galbiati Massimo Giossi PaolaLorenza Caruso Patrizia Crivori Pierre‐Alain Carrupt Bernard Testa 《Helvetica chimica acta》2001,84(8):2417-2429
A number of aminoalkoxy analogues of ipriflavone (=7‐(1‐methylethoxy)isoflavone) were prepared and examined for their capacity to inhibit bone resorption induced by bovine parathyroid hormone fragment 1 – 34. Good‐to‐high activities were found for 7‐(aminoalkoxy)isoflavone analogues. Their activity was influenced by a number of structural features, among which the length of the basic side chain, the basicity of the amino group, and the nature and position of substituents on the 3‐phenyl ring. 4′‐(Aminoalkoxy)ipriflavone derivatives were less active. 相似文献
45.
Alessandra Boschi Licia Uccelli Lorenza Marvelli Corrado Cittanti Melchiore Giganti Petra Martini 《Molecules (Basel, Switzerland)》2022,27(4)
The favorable nuclear properties in combination with the rich coordination chemistry make technetium-99m the radioisotope of choice for the development of myocardial perfusion tracers. In the early 1980s, [99mTc]Tc-Sestamibi, [99mTc]Tc-Tetrofosmin, and [99mTc]Tc-Teboroxime were approved as commercial radiopharmaceuticals for myocardial perfusion imaging in nuclear cardiology. Despite its peculiar properties, the clinical use of [99mTc]Tc-Teboroxime was quickly abandoned due to its rapid myocardial washout. Despite their widespread clinical applications, both [99mTc]Tc-Sestamibi and [99mTc]Tc-Tetrofosmin do not meet the requirements of an ideal perfusion imaging agent due to their relatively low first-pass extraction fraction and high liver absorption. An ideal radiotracer for myocardial perfusion imaging should have a high myocardial uptake; a high and stable target-to-background ratio with low uptake in the lungs, liver, stomach during the image acquisition period; a high first-pass myocardial extraction fraction and very rapid blood clearance; and a linear relationship between radiotracer myocardial uptake and coronary blood flow. Although it is difficult to reconcile all these properties in a single tracer, scientific research in the field has always channeled its efforts in the development of molecules that are able to meet the characteristics of ideality as much as possible. This short review summarizes the developments in 99mTc myocardial perfusion tracers, which are able to fulfill hitherto unmet medical needs and serve a large population of patients with heart disease, and underlines their strengths and weaknesses, the lost and found opportunities thanks to the developments of the new ultrafast SPECT technologies. 相似文献
46.
Maddalena Sguizzato Petra Martini Lorenza Marvelli Walter Pula Markus Drechsler Martina Capozza Enzo Terreno Lucia Del Bianco Federico Spizzo Rita Cortesi Alessandra Boschi 《Molecules (Basel, Switzerland)》2022,27(10)
The development of multimodal imaging techniques such as positron emission tomography (PET) and magnetic resonance imaging (MRI) allows the contemporary obtaining of metabolic and morphological information. To fully exploit the complementarity of the two imaging modalities, the design of probes displaying radioactive and magnetic properties at the same time could be very beneficial. In this regard, transition metals offer appealing options, with manganese representing an ideal candidate. As nanosized imaging probes have demonstrated great value for designing advanced diagnostic/theranostic procedures, this work focuses on the potential of liposomal formulations loaded with a new synthesized paramagnetic Mn(II) chelates. Negatively charged liposomes were produced by thin-layer hydration method and extrusion. The obtained formulations were characterized in terms of size, surface charge, efficiency of encapsulation, stability over time, relaxivity, effective magnetic moment, and in vitro antiproliferative effect on human cells by means of the MTT assay. The negatively charged paramagnetic liposomes were monodisperse, with an average hydrodynamic diameter not exceeding 200 nm, and they displayed good stability and no cytotoxicity. As determined by optical emission spectroscopy, manganese complexes are loaded almost completely on liposomes maintaining their paramagnetic properties. 相似文献
47.
Roberta Macrì Vincenzo Musolino Micaela Gliozzi Cristina Carresi Jessica Maiuolo Saverio Nucera Miriam Scicchitano Francesca Bosco Federica Scarano Stefano Ruga Maria Caterina Zito Lorenza Guarnieri Ezio Bombardelli Vincenzo Mollace 《Molecules (Basel, Switzerland)》2020,25(23)
The employment studies of natural extracts in the prevention and treatment of several diseases highlighted the role of different species of genus Ferula L., belonging to the Apiaceae family, dicotyledonous plants present in many temperate zones of our planet. Ferula communis L. is the main source of sesquiterpene ferutinin, a bioactive compound studied both in vitro and in vivo, because of different effects, such as phytoestrogenic, antioxidant, anti-inflammatory, but also antiproliferative and cytotoxic activity, performed in a dose-dependent and cell-dependent way. The present review will focus on the molecular mechanisms involved in the different activities of Ferutinin, starting from its antioxidant potential at low doses until its ionophoric property and the subsequent mitochondrial dysfunction induced through administration of high doses, which represent the key point of its anticancer action. Furthermore, we will summarize the data acquired from some experimental studies on different cell types and on several diseases. The results obtained showed an important antioxidant and phytoestrogenic regulation with lack of typical side effects related to estrogenic therapy. The preferential cell death induction for tumor cell lines suggests that ferutinin may have anti-neoplastic properties, and may be used as an antiproliferative and cytotoxic agent in an estrogen dependent and independent manner. Nevertheless, more data are needed to clearly understand the effect of ferutinin in animals before using it as a phytoestrogen or anticancer drug. 相似文献
48.
We prove that there is a constant c>0 depending only on M≥1 and μ≥0 such that
òyy+a |g(t)| dt 3 exp(-c/(ad)), ad ? (0,p],\int_y^{y+a}{ \bigl|g(t)\bigr| \, dt} \geq \exp \bigl(-c/(a\delta)\bigr), \quad a\delta \in (0,\pi], 相似文献
49.
Paola Antoniotti Lorenza Operti Roberto Rabezzana Gian Angelo Vaglio Alessandro Guarini 《Rapid communications in mass spectrometry : RCM》2002,16(3):185-191
Formation of negative ion clusters from GeH4 has been studied as a function of germane pressure, in the 25-450 mTorr range, by chemical ionisation mass spectrometry. At the lowest pressures, only the GeHn- (n = 0-3) ion family is formed, whilst at increasing pressures GemHn- (m = 1-9) ion clusters of increasing size are observed in the mass spectra. A variable contribution of the ions with different hydrogen content is observed as a function of the pressure of germane in all the GemHn- (m = 1-9) clusters. Increasing pressures induce a general increase of ion species with a low content of hydrogen atoms. In fact, at 450 mTorr, 38% of the ion current is due to the bare Gem- (m = 2-5) clusters and 83% to the sum of abundances of the GemHn- ions without hydrogen (n = 0) and with a number of hydrogen atoms not higher than the number of germanium atoms (n = 0-m). This trend suggests that a contribution of negative clusters to the deposition of the amorphous solid a-Ge:H from gaseous systems containing GeH4, activated by radiolytic methods, can enhance the formation of solids with a low hydrogen content, which show better photoelectrical properties. 相似文献
50.
Sunto Proposito di questa nota è di introdurre una classe di operatori pseudodifferenziali che agiscono su sottospazi chiusi di Wp,k(R
+), caratterizzati da opportune condizioni di compatibilità. Per tali operatori vengono studiate proprietà di Fredholm e di indice.
Research partially supported by C.N.R. Gruppo G.N.A.F.A. 相似文献 |