Initial steps in the production of H2 from ethanol: A FT-IR study of adsorbed species on Ni/MgO catalyst surface

Reactivity of pure ethanol and acetaldehyde on Ni/MgO catalyst at different reaction temperatures was investigated confirming that hydrogen production is ascribable to a series of consecutive and/or parallel reactions. FT-IR studies on adsorbed dry molecules (ethanol or acetaldehyde) showed that ethanol decomposition occurs on catalyst surface through formation of acetaldehyde, which is converted to acetates and then to carbonates, or decomposes to CO, C and H₂.     

Comparison of the medium molecular weight venom fractions from five species of common social wasps by MALDI-TOF spectra profiling

The average spectral profiles and the exact mass weight (MW) of biomolecules present in the medium fraction (from 900 to 3000 Da) of the venom of five social wasps (three European and one North American Polistes and the European hornet Vespa crabro) were determined by matrix assisted laser desorption ionization time of flight (MALDI-TOF) MS. Data were obtained analyzing the venom of single specimens (N = 46) and elaborated with the ClinProTools 2.0 (CPT) software to search for differences among the five species examined. Interesting differences in the spectral profiles were found, allowing the discrimination of venoms belonging to the different species, and their possible use as a quality control method in venom immunotherapy (VIT) for allergic patients.     

A new organogelator based on an enantiopure C2 symmetric pyrrolidine

The synthesis and the properties of a new chiral organogelator based on a C(2) symmetric pyrrolidine, are described together with its use for the synthesis of other functionalised organogelators.     

Preparation and reactivity with azo-species of hydride and dihydrogen complexes of osmium stabilised by tris(pyrazolyl)borate and phosphite ligands

Mixed-ligand OsCl(Tp)L(PPh₃) complexes 1 [Tp = hydridotris(pyrazolyl)borate; L = P(OMe)₃, P(OEt)₃ and PPh(OEt)₂] were prepared by allowing OsCl(Tp)(PPh₃)₂ to react with an excess of phosphite. Treatment of chlorocomplexes 1 with NaBH₄ in ethanol afforded hydride OsH(Tp)L(PPh₃) derivatives 2. Stable dihydrogen [Os(η²-H₂)(Tp)L(PPh₃)]BPh₄ derivatives 3 were prepared by protonation of hydrides 2 with HBF₄ · Et₂O at −80 °C. The presence of the η²-H₂ ligand is supported by short T_1 min values and J_HD measurements on the partially deuterated derivatives. Treatment of the hydride OsH(Tp)[P(OEt)₃](PPh₃) complex with the aryldiazonium salt [4-CH₃C₆H₄N₂]BF₄ afforded aryldiazene [Os(4-CH₃C₆H₄NNH)(Tp){P(OEt)₃}(PPh₃)]BPh₄ derivative 4. Instead, aryldiazenido [Os(4-CH₃C₆H₄N₂)(Tp)[P(OEt)₃](PPh₃)](BF₄)₂ derivative 5 was obtained by reacting the hydride OsH(Tp)[P(OEt)₃](PPh₃) first with methyltriflate and then with aryldiazonium [4-CH₃C₆H₄N₂]BF₄ salt. Spectroscopic characterisation (IR, ¹⁵N NMR) by the ¹⁵N-labelled derivative strongly supports the presence of a near-linear Os-NN-Ar aryldiazenido group. Imine [Os{η¹-NHC(H)Ar}(Tp){P(OEt)₃}(PPh₃)]BPh₄ complexes 6 and 7 (Ar = C₆H₅, 4-CH₃C₆H₄) were also prepared by allowing the hydride OsH(Tp)[P(OEt)₃](PPh₃) to react first with methyltriflate and then with alkylazides.     

New hybrid semiconductor materials based on viologen salts of bimetallic Fe-Pt and Fe-Au carbonyl clusters: first structural characterization of the diradical pi-dimer of the diethylviologen monocation and EPR evidence of its triplet state

The synthesis, structure, spectroscopic characterization and electrical resistivity of the [EtV](2)[Fe(4)Pt(CO)(16)], [EtV][Fe(3)Pt(3)(CO)(15)].THF, [EtV][Fe(4)Au(CO)(16)](2)2.THF (EtV=1,1'-diethyl-4,4'-bipyridilium cation) and [NEt(4)](2)[Fe(4)Au(CO)(16)] is reported. The crystal structure of [EtV](2)[Fe(4)Pt(CO)(16)] is based on infinite stacks of [(EtV)(*+)](2) pi-dimers rotated by 90 degrees and isolated [Fe(4)Pt(CO)(16)](2-) ions. Within each pi-dimer, the [EtV](*+) radical ions are perfectly eclipsed and the distance between their mean planes is 3.275 A. The EPR spectrum of the solid material at room temperature clearly indicates the presence of a significantly populated triplet state of the pi-dimer, by showing signals both at Deltam=1 and Deltam=2. The solid-state structure of [EtV][Fe(3)Pt(3)(CO)(15)].THF is based on the ionic packing of [EtV](2+) and [Fe(3)Pt(3)(CO)(15)](2-) ions, inferred from a comparison of their molecular parameters with literature data. Significant electron transfer could have been expected to give [EtV](*+)[Fe(3)Pt(3)(CO)(15)](*-) on the basis of their formal redox potentials. In spite of their different stoichiometries, the structures of [EtV][Fe(4)Au(CO)(16)](2).2 THF and [NEt(4)](2)[Fe(4)Au(CO)(16)] both contain an isomer of the monoanion [Fe(4)Au(CO)(16)](-) in solution (previously characterized in the solid state as a [NMe(3)CH(2)Ph](2)[Fe(4)Au(CO)(16)]Cl mixed salt). Resistivity measurements on pellets of powdered samples of the above compounds indicate that their tetrasubstituted ammonium salts, and complex [EtV][Fe(4)Au(CO)(16)](2)2.THF, largely behave as insulators. However, the [EtV](2)[Fe(4)Pt(CO)(16)] and [EtV][Fe(3)Pt(3)(CO)(15)].THF samples respectively display resistivities 3 and 4 orders of magnitude less than those of their corresponding ammonium salts and could be classified as semiconductor materials.     

Free silver nanoparticles synthesized by laser ablation in organic solvents and their easy functionalization

Stable colloidal solutions of free silver nanoparticles (AgNPs) have been synthesized without reducing and stabilizing agents in pure acetonitrile and N,N-dimethylformamide by laser ablation of the bulk metal. Synthesis in tetrahydrofuran and dimethyl sulfoxide gave nanoparticles surrounded by a carbon shell or included in a carbon matrix. Mie theory for free and core@shell spheres accounts for the UV-vis spectra of the nanoparticles and allows their structural characterization. Transmission electron microscopy confirms the structure of the synthesized AgNPs. It is shown that free nanoparticles can be immediately functionalized, without further treatments, in the organic solvent used for the synthesis with molecules which are soluble in the same solvent.     

Bimetallic Fe–Cu Carbido Carbonyl Clusters Obtained from the Reactions of [Fe<Subscript>4</Subscript>C(CO)<Subscript>12</Subscript>{Cu(MeCN)}<Subscript>2</Subscript>] with N-Donor Ligands

The reaction of [Fe₄C(CO)₁₂{Cu(MeCN)}₂] (1) with 3 equivalents of L–L (phen or Me₂phen) affords [Cu(L–L)₂][Fe₄C(CO)₁₂{Cu(L–L)}] (L–L = phen, 2; Me₂phen, 3) in good yields. These are protonated by strong acids resulting in [HFe₄C(CO)₁₂{Cu(L–L)}] (L–L = phen, 4; Me₂phen, 5). The reaction may be reversed with bases, resulting in the quaternary ammonium salts [NR₄][Fe₄C(CO)₁₂{Cu(phen)}] (6). 4 and 5 react with a slight excess of L–L resulting in the elimination of copper in the form of [Cu(L–L)₂]⁺ and formation of the previously reported [HFe₄C(CO)₁₂]^? homometallic cluster. Conversely, the reaction of 1 with a monodentate N-ligand such as quinoline, even if used in large excess, results in the substitution product [Fe₄C(CO)₁₂{Cu(quinoline)}₂] (8), which is then transformed into [Cu(Me₂phen)₂] [Fe₄C(CO)₁₂{Cu(quinoline)}] (9) after reaction with Me₂phen. By using the anionic cluster [Fe₅C(CO)₁₄{Cu(MeCN)}]^? instead of the neutral 1, only substitution has been observed by using both phen and quinoline, resulting in [Fe₅C(CO)₁₄{Cu(phen)}]^? (10) and [Fe₅C(CO)₁₄{Cu(quinoline)}]^? (11), respectively. Finally, the reaction of 1 with [Ru(tpy)(bpy)(N₄C-C₆H₄-CN)]Cl affords crystals of [Fe₄C(CO)₁₂Cu₂Cl{Ru(tpy)(bpy)(N₄C-C₆H₄-CN)}] (12). All compounds 2-12 have been characterized by a combination of spectroscopic (IR, NMR) and crystallographic methods. All these clusters may be viewed as composed by a butterfly [Fe₄C(CO)₁₂]^2? core bonded to Cu(I) fragments and/or H⁺ ions.     

A novel triphenylamine-based dye sensitizer supported on titania nanoparticles and the effect of titania fabrication on its optical properties

A new synthesised triphenylamine-based dye having a branched structure with one OH-ending branch able to interact with the surface hydroxyl moieties of mesoporous TiO₂ is reported. Optical properties of the dye-titania hybrid material are presented and the higher efficiency of the dye on pure anatase TiO₂ compared to the commercial Degussa P25, which contains a rutile phase component, is confirmed. The optical and chemical properties of the dye make it a promising candidate as a metal-free dye for DSSCs or as a host for a variety of transition or main group metal ions for different applications.     

Metallocene derivatives as active supports of zirconium‐based catalysts for ethene polymerization

Cyclopentadienyl magnesium chloride (MgClCp) and its functionalized derivatives represent original and interesting supporting materials to heterogenize metallocene catalysts for olefin polymerizations. The synthesis of MgClCp, its functionalization, and the preparation of a catalytic system in which the ZrCl₂(Flu)⁺ moiety is joined on the support through a cyclopentadienyl ligand are reported. This catalyst was tested in ethene polymerization, and both the catalytic activity and properties of the produced polymer were measured. Its performance was compared with that shown by the catalyst ZrCl₂CpFlu employed under the same conditions for both unsupported and conventional supports, such as MgCl₂. The results showed a remarkable improvement in terms of the activity and polymer properties with these heterogenized catalysts. Moreover, this system showed stability toward leaching processes and was characterized by good morphological control of the growing polymer. Finally, catalysts in which [HB(3,5‐Me₂pyrazolyl)₃]ZrCl and [HB(3,5‐Me₂pyrazolyl)₃]ZrClOtBu⁺ moieties were bonded to a functionalized MgClCp^? support were also synthesized and tested. The results showed that the proposed supports could be usefully used to heterogenize tailored metallocene homogeneous catalysts. In fact, new catalysts were prepared that combined the peculiar advantages of both heterogeneous and homogeneous catalysts and overcame the disadvantages of the latter, such as a lack of morphology and reactor fouling. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4243–4248, 2001