Dario Lazzari

Solvothermal synthesis and properties control of doped ZnO nanoparticles.

Indium and gallium doped ZnO nanoparticles have been prepared by a hydrothermal reaction in ethanol and methoxyethanol. A comprehensive study of the preparation process, including a thorough investigation by TG-FTIR and TG-MS of the thermal-purification procedure, is presented. Moreover, the effect of thermal conditions and dopant concentration on the structural and optical properties is discussed on the basis of XRD, TEM and UV-vis-NIR results. Reported data indicated that the use of methoxyethanol as a solvent allows an enhanced control of nanoparticle size and favours dopant incorporation into zinc oxide. Near infrared absorption of these materials can be strongly affected by increasing the doping level and upon treating nanoparticles under reducing atmosphere. Preliminary study indicated that this effect is greatly enhanced for gallium-doped zinc oxide.

ELECTROPHILIC AMINATION OF CATECHOLBORONATE ESTERS FORMED IN THE ASYMMETRIC HYDROBORATION OF VINYLARENES

Abstract (S)-(4-Methoxyphenyl)-ethyl-1,3,2-benzodioxaborole, (S)-1-(4-chlorophenyl)ethyl-1,3,2-benzodioxaborole and (S)-1-indanyl-1,3,2-benzodioxaborole, intermediates in the catalytic asymmetric hydroboration of 4-chloro- and 4-methoxystyrene, were isolated as pure oils in 75%, 84% and 49% yield respectively. For the first example, amination with N-chloromagnesio-N-methyl-O-trimethylsilylhydroxylamine gave a mixture of (S)-1-(4-methoxyphenyl)-N-methylethylamine in 33% yield, 88% e.e. and (S)-1-(4-methoxyphenyl) ethanol in 31% yield, 86% e.e.. Related results were obtained in the other cases, and the steps of catalytic hydroboration and amination could be combined in a single sequence without isolation of the intermediate. Numerous variants were carried out in the amination procedure with only marginal improvements in chemoselectivity. An investigation of the mechanism was carried out using low temperature heteronuclear NMR on 13C-1-(S)-1-(4-chlorophenyl)ethyl-1,3,2-benzodioxaborole. The dual pathway is a result of an irreversible and unselective initial step.

Silylcupration of N-phenyl-N-ethynyl-aniline: A versatile route to functionalized N,N-bis(phenyl)enamines

Abstract The silylcupration of N-phenyl-N-ethynyl-aniline, occurs regioselectively leading to silylation at the β-carbon atom. Subsequent reaction of the resulting vinyl copper adduct with electrophiles, opens a new flexible route to functionalized enamines.

EPR Imaging Determination of High Molecular Weight Nitroxide Radicals in the UV Degradation of Polycarbonate-Poly(acrylonitrile-butadiene-styrene) Polymers

The determination of nitroxide concentrations and distributions across plaques of polycarbonate/acrylonitrile-butadiene-styrene copolymer blend (PC/ABS) containing a high molecular weight hindered amine stabilizer (HALS) exposed to thermal and photochemical degradation treatments by EPR and EPR imaging (EPRI) is reported. Three different polymer compositions were examined: PC/ABS blends not-pigmented and white pre-pigmented with titanium dioxide; neat polycarbonate (PC); neat acrylonitrile-butadiene-styrene copolymer (ABS). The distribution profiles of the nitroxide radical in the various samples show large differences in the radical concentration across the plaques, these differences depending on the nature of the polymer and on the degradation treatment (thermal or photochemical). The experimental information provides important details on the mechanism of degradation of a complex polymeric matrix such as PC/ABS.

Crystal structure of 2α-(1,2-dibromoisopropyl)-5a-nitro-5ß-methyl- 1,3-dioxane, C8H13NO4Br2

C8Hi3Br2N04, monoclinic, P12i 1 (No. 4), a = 6.279(2) Ä, b = 9.308(3) Ä, c = 10.219(3) Ä, β = 90.00(5)°, V= 597.2 Ä, Ζ = 2, Rgl(F) = 0.058, wRref(F) = 0.160, T= 293 K. Source of material To a solution of 2-methyl-2-nitro-1,3-propanediol (6.75 g, 50 mmol) in concentrated H2SO4 (8.4 mL, 125 mmol), a solution of HBr (48%, 16.8 mL, 148 mmol) and H2SO4 (98%, 4 mL, 755 mmol) was added dropwise at 273 K. The reaction mixture was heated to 343 Κ and kept at this temperature for 18 h. The colorless solid that separated was filtered, dissolved in ether, washed with 10% NaHCCb, dried over Na2SC>4 and evaporated to afford a solid which was recrystallized from ether (2.5 g, 15% yield). Atom Site X y ζ t/i«, H(1A) 2a 0.0492 0.684 0.2294 0.068 H(IB) la 0.0498 0.6153 0.3697 0.068 H(3) 2a 0.3908 0.9182 0.2707 0.046 H(4A) la 0.4517 1.1710 0.2504 0.050 H(4B) 2a 0.2680 1.2754 0.2931 0.050 H(6A) 2 a 0.1564 1.0196 -0.0177 0.057 H(6B) la 0.3789 1.0065 0.0512 0.057 H(7A) la 0.4516 1.2616 0.0083 0.075 H(7B) la 0.3010 1.3805 0.0652 0.075 H(7C) la 0.2284 1.2891 -0.0557 0.075 H(8A) la 0.3901 0.7888 0.5005 0.075 H(8B) la 0.1673 0.7765 0.5687 0.075 H(8C) la 0.2627 0.9281 0.5366 0.075 Discussion The substituted 1,3-dioxane ring adopts a chair conformation, with puckering parameters [ 1 ] QT = 0.539(8) Ä and Θ2 = 1.5(8)°. In the packing mode of the title compound short C—H—O intermolecular contacts are observed between the 0 3 and 0 4 atoms of the nitro group and the Η atoms linked to the C6, C7 and C8 atoms, with C—O distances in the range 3.263(10) Ä 3.646(12) A and H---0 distances ranging from 2.54 to 2.7 4Ä. * Correspondence author (e-mail: biop02@chor.unip.it)