Gold-ruthenium compounds containing bridging phosphide or thiolate groups: Crystal structures of the intermediate species [Ru3(CO)8L(μ3-η,η,η-{Me3SiCC(C2Fc)SC(Fc)CSCCSiMe3})] (L = NMe3 or PPh2H)

New tetranuclear complexes have been prepared using bridging phosphide or thiolate groups between phosphine gold fragments and the compound [Ru₃(CO)₉(μ₃-η²,η⁴,η³-{Me₃SiCC(C₂Fc)SC(Fc)CSCCSiMe₃})]. The crystal structures of the intermediates [Ru₃(CO)₈(NMe₃)(μ₃-η²,η⁴,η³-{Me₃SiCC(C₂Fc)SC(Fc)CSCCSiMe₃})] and [Ru₃(CO)₈(PPh₂H)(μ₃-η²,η⁴,η³-{Me₃SiCC(C₂Fc)SC(Fc)CSCCSiMe₃})] have been solved.     

Measurement of PAHs in environmental matrices: results from an interlaboratory comparison on the different steps of the measurement procedure

Proficiency testing (PT) is becoming a feature of laboratory accreditation and the PT results are used to assess the technical competence of the participating laboratories. ISPRA (former APAT) plays an important role in supporting the Italian laboratories belonging to the network of the Regional Environmental Agencies to improve the quality of their analytical measurements. As a consequence, ISPRA organized an interlaboratory comparison to assess the performance of the laboratories on PAH measurement procedure. The interlaboratory comparison was drawn separating the different steps of the measurement (from the extraction to the instrumental measurement). Two matrix reference materials: (1) a polluted soil and (2) an extract reference material of the same polluted soil and a “blind” PAH mixture standard stock solution were distributed to 59 Italian laboratories. The results of interlaboratory comparison showed a significant dispersion of the PAH measurements that masks the effects of the different extraction and cleanup procedures used, but it is consistent with the results of other European interlaboratory comparisons.     

Supported Poly(Ionic Liquid)-Heteropolyacid Based Materials for Heterogeneous Catalytic Fructose Dehydration in Aqueous Medium

Two sets of four different supported catalyst materials were prepared. One set was obtained by polymerization of a bis-vinylimidazolium salt, which formed a poly(ionic liquid) coating on SiO₂, TiO₂, boron nitride BN, and carbon nitride C₃N₄. The other set was, instead, obtained by immobilizing Keggin heteropolyacid H₃PW₁₂O₄₀ onto poly-imidazolium functionalized materials. All the catalysts, including the bare supports, were subjected to physical and chemical characterization by XRD, SEM, Specific Surface Area and pore size measurements, TGA, FTIR, and acidity-basicity measurements. The catalytic activity of the materials was tested versus the fructose dehydration in water solution at two different sugar initial concentrations (0.3 and 1 M). Tests lasted 3 h with an amount of catalyst of 2 g∙L⁻¹. The presence of the poly-imidazolium on the surface of the supports increased the catalytic conversion of fructose to 5-hydroxymethylfurfural (the most abundant compound obtained) and was further improved by the contemporary presence of the heteropolyacid, at least for the highest initial fructose concentration. In the latter conditions, the highest yield of 5-hydroxymethylfurfural (>40%) was also obtained.     

The Use of UV-Visible Diffuse Reflectance Spectrophotometry for a Fast,Preliminary Authentication of Gemstones

The identification of gemstones is an important topic in the field of cultural heritage, given their enormous value. Particularly, the most important precious stones, namely diamond, emerald, ruby and sapphire, are frequently subjected to counterfeit by substitution with objects of lesser value with similar appearance, colour or shape. While a gemmologist is able to recognise a counterfeit in most instances, more generally, it is not easy to do this without resorting to instrumental methods. In this work, the use of UV-visible diffuse reflectance spectrophotometry with optic fibres (FORS) is proposed as a fast and easy method for the preliminary identification of gemstones, alternative to the classical methods used by gemmologists or to Raman spectroscopy, which is by far the instrumental method with the best diagnostic potential, but it cannot be used in situations of problematic geometric hindrance. The possibilities and the limitations given by the FORS technique are critically discussed together with the spectral features of the most important gemstones. Finally, the application of chemometric pattern recognition methods is described for the treatment of large sets of spectral data deriving from gemstones identification.     

Revealing Excited-State Trajectories on Potential Energy Surfaces with Atomic Resolution in Real Time

Photoexcited molecular trajectories on potential energy surfaces (PESs) prior to thermalization are intimately connected to the photochemical reaction outcome. The excited-state trajectories of a diplatinum complex featuring photo-activated metal–metal σ-bond formation and associated Pt−Pt stretching motions were detected in real time using femtosecond wide-angle X-ray solution scattering. The observed motions correspond well with coherent vibrational wavepacket motions detected by femtosecond optical transient absorption. Two key coordinates for intersystem crossing have been identified, the Pt−Pt bond length and the orientation of the ligands coordinated with the platinum centers, along which the excited-state trajectories can be projected onto the calculated PESs of the excited states. This investigation has gleaned novel insight into electronic transitions occurring on the time scales of vibrational motions measured in real time, revealing ultrafast nonadiabatic or non-equilibrium processes along excited-state trajectories involving multiple excited-state PESs.     

Functionalization of polyolefins by reactive processing: influence of starting reagents on content and type of grafted groups

Previous studies carried out in our laboratory on the functionalization of ethylene polymers (homo and copolymers) through free radical processes, using mechanical mixers and/or extruders with diethylmaleate (DEM) and dicumyl peroxide (DCP), have shown that the presence of branched α-olefin blocks favours degradation versus functionalization and crosslinking whereas these last are more effective with linear ethylene blocks. In this contest the present paper reports about attempts to extend the same processes to propylene polymers by benefitting of the indications of previous results. In particular the one step functionalization of EPM with two or more different groups was carried through the use of different monomers. Moreover the procedure was extended to polypropylene thus obtaining a significant functionalization degree flanked by a remarkable decrease of molecular weight.     

Adaptive Image Processing: First Order PDE Constraint Regularizers and a Bilevel Training Scheme

Journal of Nonlinear Science - We discuss a system of two coupled parabolic equations that have degenerate diffusion constants depending on the energy-like variable. The dissipation of the...     

Structure-Reactivity Insights on the Alkaline Hydrolysis of Organophosphates: Non-Leaving and Leaving Group Effects in a Bilinear Brønsted-Like Relationship

The high toxicity of organophosphates, along with its wide use as agrochemicals and chemical warfare, urges efficient degradation methods. Alkaline hydrolysis stands out, which is strongly structure-dependent. The alkaline hydrolysis of various organophosphates is described using a bilinear variation of the Brønsted equation, which evaluates concomitantly the effect of the leaving and non-leaving groups. Over 50 reactions were successfully correlated linearly and the contribution of the usually underestimated non-leaving group seems to be as important as the leaving group. The hetero atom effect (P=O and P=S) seems to vary the contribution of these groups. This concise understanding of the structure-reactivity relationship allows to predict optimal neutralization processes and is key for chemical security, saving time, resources and avoiding unnecessary manipulation of toxic chemicals.     

Acidic Deep Eutectic Solvents as Active Media for Sustainable Synthesis of Biindoles Starting from 2,2’-Diaminotolanes and Aldehydes

We describe an alternative and more sustainable method for the synthesis of 2,2’-disubstituted 3,3’-biindoles starting from 2,2’-diaminotolanes and (hetero)arylaldehydes. The key feature of the approach is the use of an acidic Deep Eutectic Solvent (DES) able to exploit a double activity, i. e., solvent and Brønsted Acid (BA) catalyst, avoiding the use of Volatile Organic Compounds (VOCs) as solvents and additional acid catalysts. By this way, we synthesized twenty-five biindoles, including eighteen new compounds. The reactions run quickly under mild conditions by microwave heating at 70 °C, with yields ranging from good to very good. The reaction scope is rather broad. The medium demonstrated to be reusable at least five times with only a slight reduction in yields. Based on experimental evidence and previous literature findings, a plausible mechanism is proposed.     

Homopolymerization of Methyl Methacrylate by Novel Ziegler‐Natta‐Type Catalysts Based on Bis(chelate)‐nickel(II) Complexes and Methylaluminoxane

Novel catalytic systems based on bis‐(chelate)nickel(II) precursors, such as bis(α‐nitroacetophenonate)nickel(II) [Ni(naph)₂] and bis(2,6‐diisopropylbenzenesalicylaldiminate)nickel(II) [Ni(dipbs)₂], and methylaluminoxane (MAO) as the cocatalyst were employed for the polymerization of methyl methacrylate (MMA). Reaction parameters were examined. Under proper conditions, the Ni(dipbs)₂/MAO system allowed to obtain poly(MMA) with a very high productivity (TOF up to 70 000 h^–1) and a remarkable syndiospecificity degree (rr > 80%) at room temperature without addition of an ancillary Lewis base.