Comparison between triplet and singlet molecular oxygen oxidation of fully substituted alkoxyoxazoles

Oxidation by ground-state molecular oxygen of fully substituted alkoxyoxazoles I gave imines IV as major products; diacylcarbamates III were also obtained as minor products. The free radical nature of the autoxidation was established. A mechanistic interpretation of the results is suggested also in the light of the results of the oxidation with singlet oxygen.     

Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes

Gold(I) dicarbene complexes [Au₂(MeIm‐Y‐ImMe)₂](PF₆)₂ (Y=CH₂ ( 1 ), (CH₂)₂ ( 2 ), (CH₂)₄ ( 4 ), MeIm=1‐methylimidazol‐2‐ylidene) react with iodine to give the mixed‐valence complex [Au(MeIm‐CH₂‐ImMe)₂AuI₂](PF₆)₂ ( 1 a^I ) and the gold(III) complexes [Au₂I₄(MeIm‐Y‐ImMe)₂](PF₆)₂ ( 2 c^I and 4 c^I ). Reaction of complexes 1 and 2 with an excess of ICl allows the isolation of the tetrachloro gold(III) complexes [Au₂Cl₄(MeIm‐CH₂‐ImMe)₂](PF₆)₂ ( 1 c^Cl ) and [Au₂Cl₄(MeIm‐(CH₂)₂‐ImMe)₂](Cl)₂ ( 2 c^Cl‐Cl ) (as main product); remarkably in the case of complex 2 , the X‐ray molecular structure of the crystals also shows the presence of I‐Au‐Cl mixed‐sphere coordination. The same type of coordination has been observed in the main product of the reaction of complexes 3 or 4 with ICl. The study of the reactivity towards the oxidative addition of halogens to a large series of dinuclear bis(dicarbene) gold(I) complexes has been extended and reviewed. The complexes react with Cl₂, Br₂ and I₂ to give the successive formation of the mixed‐valence gold(I)/gold(III) n a^X and gold(III) n c^X (excluding compound 1 c^I ) complexes. However, complex 3 affords with Cl₂ and Br₂ the gold(II) complex 3 b^X [Au₂X₂(MeIm‐(CH₂)₃‐ImMe)₂](PF₆)₂ (X=Cl, Br), which is the predominant species over compound 3 c^X even in the presence of free halogen. The observed different relative stabilities of the oxidised complexes of compounds 1 and 3 have also been confirmed by DFT calculations.     

Multispectral satellite imagery processing to recognize the archaeological features: The NW part of Mount Etna (Sicily,Italy)

We propose a new GIS-based procedure to retrieve archaeological elements using satellite remote sensing. The processing of multispectral satellite images consists in a preprocessing phase using the pansharpening technique to improve the spatial quality and in the exploitation of linear equations of the initial spectral bands with the aim of generating accurate and precise raster data that can be used as input for an object classification. The proposed methodology has been tested in an archaeological area located on the north-west flank of Etna volcano (Sicily, Italy).     

Sustainable Electrochemically‐Mediated Atom Transfer Radical Polymerization with Inexpensive Non‐Platinum Electrodes

Electrochemically‐mediated atom transfer radical polymerization (eATRP) of oligo(ethylene oxide) methyl ether methacrylate in water is investigated on glassy carbon, Au, Ti, Ni, NiCr and SS304. eATRPs are performed both in divided and undivided electrochemical cells operating under either potentiostatic or galvanostatic mode. The reaction is fast, reaching high conversions in ≈4 h, and yields polymers with dispersity <1.2 and molecular weights close to the theoretical values. Most importantly, eATRP in a highly simplified setup (undivided cell under galvanostatic mode) with inexpensive nonnoble metals, such as NiCr and SS304, as cathode is well‐controlled. Additionally, these electrodes neither release harmful ions in solution nor react directly with the C X chain end and can be reused several times. It is demonstrated that Pt can be replaced with cheaper, and more readily available materials without negatively affecting eATRP performance.

     

High Surface Area Mesoporous Silica Nanoparticles with Tunable Size in the Sub-Micrometer Regime: Insights on the Size and Porosity Control Mechanisms

Mesoporous silica nanostructures (MSNs) attract high interest due to their unique and tunable physical chemical features, including high specific surface area and large pore volume, that hold a great potential in a variety of fields, i.e., adsorption, catalysis, and biomedicine. An essential feature for biomedical application of MSNs is limiting MSN size in the sub-micrometer regime to control uptake and cell viability. However, careful size tuning in such a regime remains still challenging. We aim to tackling this issue by developing two synthetic procedures for MSN size modulation, performed in homogenous aqueous/ethanol solution or two-phase aqueous/ethyl acetate system. Both approaches make use of tetraethyl orthosilicate as precursor, in the presence of cetyltrimethylammonium bromide, as structure-directing agent, and NaOH, as base-catalyst. NaOH catalyzed syntheses usually require high temperature (>80 °C) and large reaction medium volume to trigger MSN formation and limit aggregation. Here, a successful modulation of MSNs size from 40 up to 150 nm is demonstrated to be achieved by purposely balancing synthesis conditions, being able, in addition, to keep reaction temperature not higher than 50 °C (30 °C and 50 °C, respectively) and reaction mixture volume low. Through a comprehensive and in-depth systematic morphological and structural investigation, the mechanism and kinetics that sustain the control of MSNs size in such low dimensional regime are defined, highlighting that modulation of size and pores of the structures are mainly mediated by base concentration, reaction time and temperature and ageing, for the homogenous phase approach, and by temperature for the two-phase synthesis. Finally, an in vitro study is performed on bEnd.3 cells to investigate on the cytotoxicity of the MNSs.     

Effect of compatibilization on thermal degradation kinetics of HDPE-based composites containing cellulose reinforcements

Dynamic thermogravimetric analysis under nitrogen flow was used to investigate the thermal decomposition process of high-density poly(ethylene) (HDPE)-based composites reinforced with cellulose fibers obtained from the recycling of multilayer carton scraps, as a function of the cellulose content and the compatibilization. The Friedman, Flynn–Wall–Ozawa, and Coats–Redfern methods were used to determine the apparent activation energy (E _a) of the thermal degradation of the cellulose component into the composites. E _a has been found dependent on the cellulose amount and on the cellulose/polymer matrix interfacial adhesion. In particular, it has been evidenced an increase of the cellulose thermal stability as a consequence of the improved interfacial adhesion between the components in NFR composites.     

Evaluation of signal and noise and identification of a suitable target function in the tuning of an ESI ion trap mass spectrometer by multivariate pattern recognition tools

When mass spectrometry is not combined to separation techniques, the evaluation of signal and noise in a complex mass spectrum is not trivial. The tuning of the spectrometer based only on the increase of the signal of a selected number of m/z values does not ensure the achievement of the best experimental conditions: signal could improve and noise could increase as well. The scope of this work is the development of a function separating signal and noise (for evaluating the S/N) from complex mass spectra for potential use as target function for the automatic tuning of the instrument. Two different methods were applied: the first is based on the separation of a pool of m/z values attributable to the signal from the m/z values due to the noise, while the second is based on the application of principal component analysis to separate the signal (present in the significant components) from the noise (present in the residuals). The comparison of the two methods was carried out by the evaluation of the stability of the signal and the target functions obtained, and the evaluation of the variation of the target functions as a function of concentration.     

Synthesis of sulfated galactocerebrosides from an orthogonal beta-D-galactosylceramide scaffold for the study of CD1-antigen interactions

CD1a protein binds sulfatide (3-O-sulfo-beta-D-galactosylceramide) to form an antigen complex that interacts with T cell receptors and activates T cells. To assess the role of the position of the sulfate in T cell activation, the synthesis of three beta-D-galactosylceramides, variously bearing a sulfate at position 2, 4, or 6 of galactose, has been planned and carried out. The compounds were synthesized by an orthogonal sulfation strategy from a common beta-D-galactosylceramide scaffold, which was in turn obtained through an efficient glycosylation reaction between a fully orthogonally protected galactosyl imidate and 3-O-benzoylazidosphingosine. Immunological evaluation of the three sulfated compounds in CD1a-mediated T cell activation, in comparison with natural sulfatide, provided evidence of the influence of the sulfate position in the recognition event between the antigen, the CD1 protein and the T cell receptor.