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Long-Lived Radical Cation Salts Obtained by Interaction of Monocyclic Arenes with Niobium and Tantalum Pentahalides at Room Temperature: EPR and DFT Studies
No full textThe 1:3 reactions of the alkoxy arenes 1,4-(MeO)2C6H4
and 1,4-F2-2,5-(MeO)2C6H2 with TaF5 in chloroform at 40–508C resulted in for-mation in about 35% yield of the long-lived radical cation salts [1,4-(MeO)2C6H4][Ta2F11](2a) and [1,4-F2-2,5-(MeO)2C6H2][Ta2F11](2b), respectively. The non-alkoxy-substituted [arene][M2X11][M=Ta, X=F: arene=
C6H5Me (2c), 1,4-C6H4Me2 (2d), C6H5F (2e), C6H5NO2
(2f); M=Nb, X=F: arene=C6H5Me (4a), 1,4-C6H4Me2 (4b), C6H5F(4c), C6H5NO2 (4d); M=Ta, X=Cl: arene=1,4-C6H4Me2 (5)] were obtained from the 3:1 reactions of MX5
with the appropriate arene in chloroform at temperatures in the range 40–90°C. Compounds 2–5 were detected by EPR
spectroscopy (in CHCl3) at room temperature, and their gas-phase structures were optimized by DFT calculations.
Formation of the MIV species [MX4(NCMe)2][M=Ta, X=F(3a); M=Nb, X=F(3b); M=Ta, X=Cl (3c)] was ascertained by EPR spectroscopy on solutions obtained by treatment of the reaction mixtures with acetonitrile.
Non-selective reactions occurred upon combination of 1,4-F2-2,5-(MeO)2C6H2 with AgNbF6 (in CH2Cl2) and 1,4-(MeO)2C6H4 with SbF5
Antioxidant properties of food products containing lycopene are increased by the presence of chlorophyll
No full textA diet based on the consumption of fresh fruits such as tomato has been associated with health protection and longevity, due to their nutraceutical value. The latter is influenced by the presence of antioxidant compounds such as vitamin C (ascorbic acid), vitamin E (tocopherol), carotenoids, flavonoids as well as phenolic acids. Indeed, these molecules are able to neutralize reactive oxygen species (ROS) and, for this reason, are worldwide recognized as beneficial for preventing human diseases among which cancer and cardiovascular pathologies.
Lycopene is a natural pigment synthesized by photosynthetic plants and represents the most abundant carotenoid in tomatoes, being present in concentrations ranging from 9-150 mg/Kg depending on the variety. The increase in dietary lycopene has been associated to a decreased risk of chronic diseases and one of the possible mechanisms involved in this action is represented by its antioxidant activity.
Lycopene as well as chlorophyll are lipophilic antioxidants, contributing to the antioxidant activity of tomato berries and leaves. However, the antioxidant activity of lipid extract from leaves was shown to be 45-70-fold higher than that from berries. This is because chlorophyll behaves as a fast lipophilic antioxidant (FLA), accounting for the 38% of FLA present in the lipid extract from leaves, whereas lycopene can be classified as a slow lipophilic antioxidant (SLA) responsible for the 40% of the antioxidant activity due to the slow fraction of the lipid extract from berries. Moreover, the presence of chlorophyll in a mixture containing lycopene increased the antioxidant activity compared to lycopene alone.
The role of chlorophyll for human health, for example in reducing risk of colon cancer, is more and more recognized by scientific community and its presence in food products such as not-fully ripe berries could substantially increase their nutritional value, in combination with high concentrations of lycopene
Reactions of molybdenum pentachloride with oxygen and nitrogen donor ligands
No full textThe interactions of molybdenum pentachloride (1) with a variety of organic compounds were studied in dichloromethane and the metal products were isolated in the solid state. The 3:1 molar reactions of 1 with OCRR′ (R = R′ = Ph; R = H, R′ = 2-C6H4Me) afforded the complexes Mo(O)Cl3(OCRR′)2 (R = R′ = Ph, 2a; R = H, R′ = 2-C6H4Me, 2b) in high yields. Compound , 3, was isolated in 35% yield from 1 and 2-acetylfuran. The 1:1 reaction of 1 with phenazine (C12H8N2) 1 resulted in the formation of MoCl5(C12H8N2), 4; the oxydo-chloride derivative Mo(O)Cl3[κ1(N)-C12H8N2], 5, was prepared straightforwardly by addition of phenazine to Mo(O)Cl3, formed in situ upon treatment of 1 with tetrahydrofuran. The addition of a twofold excess of Me2NCH2CH2CO2Me to 1 afforded MoCl4[κ1(N)-Me2NCH2CH2CO2Me]2, 6, in 72% yield. The reaction of 1 with MeO2CCtriple bond; length of mdashCCO2Me led to a mixture of inseparable products: MoOCl3(κ1-MeO2CCtriple bond; length of mdashCCO2Me)2, 7a, MoCl5(κ1-MeO2CCtriple bond; length of mdashCCO2Me), 7b, and MoCl4(κ1-MeO2CCtriple bond; length of mdashCCO2Me)2, 7c, were recognized by combined EPR/DFT investigation. Analogous DFT/EPR studies were performed on 2b and 4. The X-ray structures of 2a, 3 and 5 were determined; the X-ray structure of 5 represents a rare example of crystallographically-characterized pentacoordinated Mo(V) neutral complex
Coordination Environment of Highly Concentrated Solutions of Cu(II) in Ionic Liquids through a Multidisciplinary Approach
No full textThe coordination environment around CuII in highly concentrated solutions of copper(II) salts (CuCl2 and Cu(Tf2N)2) in two pure ionic liquids bearing the same anion, namely, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]) and 1-butyl-3-methylimidazolium chloride ([bmim]Cl), is investigated by X-ray photoelectron spectroscopy (XPS), UV/Vis spectroscopy, EPR spectroscopy and DFT calculations. Moreover, the electrochemical behavior of these mixtures is studied. Whereas reversible reduction of CuII to copper metal can be observed in the 1:1 [bmim][Tf2N]:Cu(Tf2N)2 solution, 2:1 and 1:1 [bmim]Cl:CuCl2 mixtures showed one-electron reduction of CuII to CuI with formation of a permanent deposit of CuCl. XPS, UV/Vis and EPR spectra as well as DFT calculations suggest the formation in [bmim]Cl of dynamic coordination complexes arising from the interaction between CuCl2 and [bmim]+Cl- . The two long-lived situations are probably trigonal and deformed tetrahedral copper(II) chloride coordination complexes ([CuCl3]- and [CuCl4]2-, respectively)
Chemistry of Interfacial Interactions in a LDPE-Based Nanocomposite and Their Effect on the Nanoscale Hybrid Assembling
No full textThe selective solvent extraction of a LLDPE nanocomposite, prepared by using a LLDPE functionalized with maleic anhydride and an organo-modified montmorillonite (OMMT), allowed the separation of two fractions containing different contents of the starting OMMT and characterized by different morphological, dynamical, and thermal properties as revealed by WAXD, SAXS, TEM, DSC, and dielectric analysis. FTIR spectroscopy was used to confirm the degree of dispersion of the nanoparticles and to highlight the nature of chemical bonds that generate hybrid assembled structures responsible for changes in solubility, mobility, and thermal properties of the polymer chains strongly interacting with the inorganic substrate. In particular, a deconvolution procedure of the profile of carbonyl bands of functionalized polymer chains in the different fractions, together with an accurate attribution of the signals (through theoretical simulation and calculation of possible structures and their FTIR spectra), assessed the occurrence of reactions between the different functionalities of polymers and inorganic surface
Interaction of Azole Compounds with DOPC and DOPC/Ergosterol Bilayers by Spin Probe EPR Spectroscopy: Implications for Antifungal Activity
No full textCharacterization of an amylose-graft-poly(n-butyl methacrylate) copolymer obtained by click chemistry by EPR and SS-NMR spectroscopies
No full textWe present an investigation of the main chemical and physico-chemical properties of a graft copolymer of amylose and poly(n-butyl methacrylate), Am-g-PBMA, amphiphilic and able to self-assemble in water, prepared by coupling end azide-functionalized PBMA and alkyne-functionalized amylose under convenient click conditions. A deep knowledge of these properties is necessary in the perspective of real applications of the copolymer. To this aim we combined a basic characterization through FT-IR, TGA, ICP-OES and SEM with an extensive EPR and Solid State NMR investigation. It was possible to characterize the main structural and dynamic properties of Am-g-PBMA and highlight the presence of residual copper (Cu(II)) from the catalyst, even after an extensive purification procedure. We could identify two main species of Cu(II): Cu(II) complexes coordinated to the N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) ligand from the catalyst and to the copolymer triazole nitrogens and multi-nuclear or clustered Cu(II) species likely coordinated to amylose hydroxyl groups
The Redox Chemistry of [Co6C(CO)15]2–: A Synthetic Route to New Co-Carbide Carbonyl Clusters
No full textThe oxidation and reduction reactions of [Co6C(CO)(13)](2-) have been studied in detail, leading to the isolation of several new Co-carbide carbonyl clusters. Thus, [Co6C(CO)(15)](2-) reacts in tetrahydrofuran (THF) with oxidants such as HBF4 center dot Et2O and [Cp2Fe][PF6], resulting first in the formation of the previously reported [Co6C(CO)(14)](-); then, in CH2Cl2, the new dicarbide [Co11C2(CO)(23)](2-) is formed. The latter may be further oxidized, yielding the isostructural monoanion [Co11C2(CO)(23)](-), whereas its reduction with (cyclopentadienyl)(2)Co affords the unstable trianion [Co11C2(CO)(23)](3-), which decomposes during workup. Oxidation of [Co6C(CO)(15)](2-) in CH3CN with [C7H7][BF4] affords the same major products, and besides, the new monoacetylide [Co-10(C-2)(CO)(21)](2-) was obtained as side-product. Conversely, the reduction of [Co6C(CO)(15)](2-) in THF with increasing amounts of Na/naphthalene results in the following species: [Co6C(CO)(13)](2-), [Co-11(C-2)(CO)(22)](3-), [Co7C(CO)(15)](3-), [Co8C(CO)(17)](4-), [Co6C(CO)(12)](3-), and [Co(CO)(4)](-). The new [Co11C2(CO)(23)](-), [Co11C2(CO)(23)](2-), [Co-10(C-2)(CO)(21)](2-), [Co8C(CO)(17)](4-), [CO6C(CO)(12)](3-), and [Co7C(CO)(15)](3-) clusters were structurally characterized. Moreover, the paramagnetic species [Co11C2(CO)(23)](2-) and [Co6C(CO)(12)](3-) were investigated by means of electron paramagnetic resonance spectroscopy. Finally, electrochemical studies were performed on [Co11C2(CO)(23)](n-) (n = 1-3)
Reactive Oxygen Species and Photosynthetic Functioning: Past and Present
No full textThe present chapter begins by presenting the basic introduction to Reactive Oxygen Species (ROS), then detailng the current knowledge in ROS research. In particular, Electron Paramagnetic Resonance (EPR) technique applicability in photosynthesis research was considered. Kinetics of superoxide formation by illuminated thylakoids was shown. The progress of the knowledge on the different sites of photosynthetic membranes involved in ROS formation was reported and the main defense mechanisms occurring in the chloroplast to detoxify from ROS were decribed
Effects of azole treatments on the physical properties of Candida albicans plasma membrane: A spin probe EPR study
No full textEPR spectroscopy was applied to investigate the effects of the treatment of Candida albicans cells with fluconazole (FLC) and two newly synthesized azoles (CPA18 and CPA109), in a concentration not altering yeast morphology, on the lipid organization and dynamics of the plasma membrane. Measurements were performed in the temperature range between 0°C and 40°C using 5-doxyl- (5-DSA) and 16-doxyl- (16-DSA) stearic acids as spin probes. 5-DSA spectra were typical of lipids in a highly ordered environment, whereas 16-DSA spectra consisted of two comparable components, one corresponding to a fluid bulk lipid domain in the membrane and the other to highly ordered and motionally restricted lipids interacting with integral membrane proteins. A line shape analysis allowed the relative proportion and the orientational order and dynamic parameters of the spin probes in the different environments to be determined. Smaller order parameters, corresponding to a looser lipid packing, were found for the treated samples with respect to the control one in the region close to the membrane surface probed by 5-DSA. On the other hand, data on 16-DSA indicated that azole treatments hamper the formation of ordered lipid domains hosting integral proteins and/or lead to a decrease in integral protein content in the membrane. The observed effects are mainly ascribable to the inhibition of ergosterol biosynthesis by the antifungal agents, although a direct interaction of the CPA compounds with the membrane bilayer in the region close to the lipid polar head groups cannot be excluded
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