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Palladium(II)- or copper(II)-catalysed solution-phase oxyfunctionalization of methane and other light alkanes by hydrogen peroxide in trifluoroacetic anhydride
No full text[(Ir(C5Me5)(CO))6Hg8][CF3CO2]6, a Mixed-Metal Cluster with an Ir6Hg6 Twelve-Membered Ring and Additional Hg Centres and Metal-Metal Bonds
No full textA [4π+4π] intramolecular photocyclomer of 9-anthroic anhydride: 5,6,11,12-tetrahydro-5,12;6,11-di-o-benzenodibenzo[a,e]cyclooctene-5, 6-dicarboxylic anhydride
No full textThe title compound, C30H18O3, was obtained by light irradiation of a dichloroethane solution of 9-anthroyl chloride and 9-anthroic acid. The molecules, which possess approximately mm2 local symmetry, are packed in columns, the oxygenated moieties facing each other according to the symmetry of a monoclinic lattice. The space group of the crystal is P21/c, with a whole molecule as the asymmetric unit. The structure is compared with those of similar dianthracene derivatives
Chromotropic guaiazulene-derived radical scavengers for the detection of oxygen-centred radicals in micellar media
No full textGuaiazulene-based phenolic radical scavengers: synthesis, properties, and EPR studies of their reaction with oxygen-centred radicals
No full textA variety of phenolic derivatives 4, carrying the guaiazulene moiety, were prepared starting from guaiazulene. Compounds 4 react with oxygen-centred radicals exhibiting chromotropic behaviour. The radical scavenging power of these compounds was evaluated by different methods. Compounds 4 are less efficient than some of the most common radical scavengers but show quite selective behaviour towards different oxygen-centred radicals. A correlation is found between the antioxidant activity of the compounds 4 and the corresponding phenolic O-H bond dissociation energy. Some aspects of the reaction of the compounds 4 with oxygen-centred radicals were elucidated by EPR and DFT studies
9-Anthroylacetone and its photodimer
No full text9-Anthroylacetone undergoes a head-to-tail [4π+4π] photo-dimerisation reaction that leads to the formation of 5,11-bis(1,3-diketobutyl)-5,6,11,12- tetrahydro-5,12,6,11-di-o-benzeno-dibenzo[a,e]cyclooctene both in solution and in the solid state when irradiated with different sources (sunlight, tungsten lamp, xenon lamp, UV laser beam 351-364 nm), the reaction being accompanied by a colour variation from bright yellow to colourless. Quantum yields >0.023 mol/Einstein are evaluated for the solid state reaction. Interestingly, the dimer dissociates to give 9-anthroylacetone, both thermally (T>130°C) and photochemically, by short UV wavelength irradiation. The single-crystal X-ray structure of 9-anthroylacetone and its dimer are reported. 9-Anthroylacetone undergoes a head-to-tail [4π+4π] photo-dimerisation reaction both in solution and in the solid state when irradiated with different sources; the dimer reversibly dissociates into 9-anthroylacetone, both thermally and photochemically
Radical Species from Transition Metal Complexes. II. ESR Study of the Reaction of Alkyl-Substituted ß-Ketoenolates of Cobalt(III) with Trifluoroacetic Acid
No full textSynthesis of 9-Anthrylmethyl-Functionalised Cyclopentadienyl Derivatives of Rhodium(I) and Iridium(I) and Study of their Luminescence Properties
No full textThe compound 9-anthrylmethylcyclopentadiene 1 was prepared by reacting 9-bromomethylanthracene with cyclopentadienylsodium and transformed into its thallium(I) derivative on reaction with thallium ethoxide 3. The 9-anthrylmethylcyclopentadienyl (AnCH2C5H4) derivatives of rhodium(I) and iridium(I) of formula [M(η5-AnCH2C5H4)L2] (M=Rh or Ir; L=C2H4, CO, PPh3, C8H14; L2=C7H8, 1,5-C8H12) 4-6 and 9-11 were obtained in good yields by reacting the corresponding rhodium(I) and iridium(I) chlorides with 3. Both [Rh(η5-AnCH2C5H4)(η2-C2H4)2] (4) and [Rh(η5-AnCH2C5H4)(CO)2] (5) react with triphenylphosphine, at 130°C to give [Rh(η5-AnCH2C5H4)(η2-C2H4)(PPh3)] (7) and [Rh(η5-AnCH2C5H4)(CO)(PPh3)] (8). All complexes were characterised by elemental analysis, mass spectrometry, 1H-NMR and FTIR. The structures of two of them, i.e. [Rh(η5-AnCH2C5H4)(η2-C2H4)2] (4) and [Rh(η5-AnCH2C5H4)(CO)2] (5), were elucidated by single crystal X-ray diffraction. Compound 4 crystallises in the triclinic space group P1̄ with a=11.112(1), b=12.065(1), c=15.982(2) Å; α=99.83(1), β=107.86(1), γ=107.22(1)°. V=1865.6(3) Å3. Z=4, Dcalc=1.475 g cm-1, R1=0.0414 [I>2σ(I)], wR2=0.0953. Compound 5 crystallises in the triclinic space group P1̄ with a=12.232(1), b=13.463(1), c=13.488(1) Å; α=61.25(1), β=68.51(1), γ=67.45(1)°. V=1752.5(2) Å3. Z=4, Dcalc=1.570 g cm-1, R1=0.0313 [I>2σ(I)], wR2=0.0795. The UV-vis spectra (280-700 nm) of 1 and of complexes 4-11 were recorded. The spectra of 4-11 are indicative of important interactions between the anthrylic chromophore and the cyclopentadienyl-metal moiety. When excited at 365 nm, 1 results to be an efficient light-emitting molecule, while its derivatives 4-11 are poorly luminescent compounds. Indeed, all complexes exhibit similar fluorescence spectra which are typical of the anthrylic fluorophore but have extremely low intensity (the one observed for 9-methylanthracene was below 5% and taken as the reference compound). The mechanism of fluorescence quenching in the complexes 4-11 is discussed
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