Copper (II) metallocycles as anions receptors. Further studies on their synthesis, spectroscopic and spectrometric characterization in solution

Copper (II) metallocycles as anions receptors. Further studies on their synthesis, spectroscopic and spectrometric characterization in solution Rossana Galassia, Camille S. Oumaroua, Alfredo Burinia, Massimiliano Lupacchinia, Stefania Pucciarellib a School of Science and Technology, Università di Camerino, Via Sant’Agostino 1, 62032, Camerino, Italia b School of Biosciences and Biotechnology, University of Camerino, Via Gentile III da Varano, 1, 62032 Camerino, Italy [email protected] Halide-centered hexanuclear, anionic copper (II) pyrazolate complexes [trans-Cu6{(3,5-CF3)2pz}6(OH)6X]-, X= Cl, Br, I can be isolated in a good yield from the redox reaction of the trinuclear copper(I) pyrazolate complex [µ-Cu3{(3,5-CF3)2pz}3] with a halide source such as Ph3PAuCl, [Bu4N]X, X= Cl, Br or I or PPN(NO2) where PPN is bis(triphenylphosphoranylidene)ammonium [1]. We reported in this work a new route for the synthesis of the [trans-Cu6{(3,5-CF3)2pz}6(OH)6X] starting from the neutral 3,5-(CF3)2pzH. The reactions showed lower yields but fast conversion to the corresponding halide centered metallocycles. A water centered metallocycle was obtained too. The nature of the molecule inside the cavity was discussed by IR spectroscopy, X-ray structural data and by determining the rate constant of the water exchange reaction in acetone solution. The mechanism likely involves the formation of pyrazoles self-aggregates by intermolecular hydrogen bonding. From data analysis, we can assume that the cavity is very affine for chloride and bromide but scarcely selective, while is slightly less affine for iodide. [1] A. A. Mohamed, S. Ricci, A. Burini, R. Galassi Inorg. Chem. 2011, 50, 1014-1020

Deoxydehydration of glycerol in presence of rhenium compounds: reactivity and mechanistic aspects

International audienceAllyl alcohol (AA) was obtained by the deoxydehydration (DODH) of glycerol performed in the presence of a number of Re compounds (oxides, phosphine and halide derivatives) in alcoholic solvent or in neat conditions. Independently of starting Re species, the resulting catalytic process featured a delay time, necessary to start the formation of both AA and an Re-alkoxide precipitate. However, no delay time was detected by operating DODH using a preformed precipitate obtained by either Re source. As a consequence, and based on IR spectral analysis, it was hypothesized that the Re precipitate is the actual catalyst of DODH. The mechanism of DODH catalysis operated by methyltrioxorhenium (MTO) was studied by experimental and theoretical approaches. The results suggest that MTO releases methane with the formation of an ReVII alkoxide that subsequently aggregates by yielding the precipitate. The ReVII centre precipitate surface then undergoes reduction by forming ReV catalytic spots. The calculated kinetics also indicate that the detected latency can be ascribed to the presence of two high barriers, i.e. methane release and ReVII → ReV reduction, whereas the downstream processes, i.e. glycation and AA release, are not rate determining

Poly(ethylene glycol)s as grinding additives in the mechanochemical preparation of highly functionalized 3,5-disubstituted hydantoins

International audienceThe mechanochemical preparation of highly functionalized 3,5-disubstituted hydantoins was investigated in the presence of various poly(ethylene) glycols (PEGs), as safe grinding assisting agents (liquid-assisted grinding, LAG). A comparative study under drygrinding conditions was also performed. The results showed that the cyclization reaction was influenced by the amount of the PEG grinding agents. In general, cleaner reaction profiles were observed in the presence of PEGs, compared to dry-grinding procedures

From Molecules to Silicon-Based Biohybrid Materials by Ball Milling

Hybrid nanoparticles with a large bridging organic group were prepared by mechanochemical-assisted sol–gel reaction. Planetary ball mill (PBM) was used for the first time to access the bis-silylated precursors, containing complex functionalities (such as hydantoins or a symmetrical urea obtained from α-amino esters). The process is based on a sequential reaction pathway involving liquid-assisted grinding (LAG) and 1,1′-carbonyldimidazole (CDI)-mediated one-pot/two-step reactions. Then hydantoins and the symmetric urea were used for the one-pot preparation of the corresponding bis-silylated compounds in a vibrational ball mill (VBM), followed by the mechanochemical sol–gel preparation of biohybrid bridged silsesquioxane nanospheres of uniform size