The anthryl-substituted rhodium(III) and iridium(III) heteroleptic β-ketoenolato derivatives of general formula M(acac)2(anCOacac) acac = pentane-2,4-dionate; anCOacac = ...3-(9-anthroyl)pentane-2,4-dionate, 3 (M = Rh) and 4 (M = Ir), and M(acac)2(anCH2acac) anCH2acac = 3-(9-anthrylmethyl)pentane-2,4-dionate, 5 (M = Rh) and 6 (M = Ir), were prepared by reacting the corresponding tris(pentane-2,4-dionate)metal complexes, M(acac)3, with 9-anthroyl chloride and 9-chloromethylanthracene, respectively, under Friedel−Crafts conditions. 3−6 were characterized by elemental analysis, ion spray mass spectrometry (IS-MS), 1H NMR, and UV−vis spectroscopy. The structure of 3 was also elucidated by single-crystal X-ray analysis. When excited at 365 nm, 3−6 result to be poorly luminescent compounds; while the free diketone, i.e., 3-(9-anthrylmethyl)pentane-2,4-dione 1, whose structure was established also by single-crystal X-ray analysis, results to be a strongly light emitting molecule. The study of the electrochemical behavior of 3−6 as well as of the corresponding tris-acetylacetonates of rhodium(III) and iridium(III) allows a satisfactory interpretation of their electrode process mechanism, and gives information about the location of the redox sites along with the thermodynamic and kinetic characterization of the corresponding redox processes. All data are in agreement with the hypothesis that the quenching of the anthracene fluorescence, observed for compounds 3−6, can be due to an intramolecular electron transfer process between the anthryl moiety and the metal−β-ketoenolato component. Moreover, a study was carried out of the redox behavior of the dyads 3−6 under chemical activation. The one-electron oxidation of compounds 3−6 by thallium(III) trifluoroacetate leads to the formation of the corresponding cation radicals, 3 + −6 + , whose highly resolved X-band EPR spectra were fully interpreted by computer simulation as well as by semiempirical and DFT calculations of spin density distribution.
The 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 (AnCH
2C
5H
4) derivatives of rhodium(I) and iridium(I) of formula M(η
5-AnCH
2C
5H
4)L
2 (M=Rh or Ir; L=C
2H
4, CO, PPh
3, C
8H
14; L
2=C
7H
8, 1,5-C
8H
12)
4–
6 and
9–
11 were obtained in good yields by reacting the corresponding rhodium(I) and iridium(I) chlorides with
3. Both Rh(η
5-AnCH
2C
5H
4)(η
2-C
2H
4)
2 (
4) and Rh(η
5-AnCH
2C
5H
4)(CO)
2 (
5) react with triphenylphosphine, at 130°C to give Rh(η
5-AnCH
2C
5H
4)(η
2-C
2H
4)(PPh
3) (
7) and Rh(η
5-AnCH
2C
5H
4)(CO)(PPh
3) (
8). All complexes were characterised by elemental analysis, mass spectrometry,
1H-NMR and FTIR. The structures of two of them, i.e. Rh(η
5-AnCH
2C
5H
4)(η
2-C
2H
4)
2 (
4) and Rh(η
5-AnCH
2C
5H
4)(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) Å
3.
Z=4,
D
calc=1.475 g cm
−1,
R
1=0.0414
I>2
σ(
I),
wR
2=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) Å
3.
Z=4,
D
calc=1.570 g cm
−1,
R
1=0.0313
I>2
σ(
I),
wR
2=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.
A variety of chiral 6-hepten-1-ynes have been found to undergo cyclization to titanabicyclopentenes by (η
2-propene)Ti(O
i-Pr)
2 with excellent yields and degrees of
exo-stereoselectivity depending ...on the substrate steric requirements. In the framework of a plausible cyclization mechanism several conformational features which can regulate the stereoinduction have been suggested.
The 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.
En el presente articulo se analizan los datos oficiales de FAO sobre la pesca del coral rojo en el Mediterraneo occidental. Se discute la tendencia de dicha pesca, ya sea en su conjunto general como ...individualmente, en cada pais productor. De este estudio ha resultado una clara tendencia a la disminucion del producto entre 1983 y 1991. Italia, Espana y Tunez han mostrado tal tenencia decreciente. Por el contrario, en Francia se mantiene casi constantemente una produccion moderada. En Marruecos se ha comprobado un boom y una caida de la produccion dando a entender que una pequena cantidad ha sido super-explotada velozmente, empobreciendo de este modo el stock de coral. Argelia, sin embargo, se muestra como la unica region del Mediterraneo occidental donde la pesca del coral rojo ha aumentado, seguramente gracias a la extension de sus bancos coralinos. En este ambito, los conocimientos actuales de parametros demograficos y de caracteristicas de las poblaciones del coral rojo son considerados y discutidos.
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![A [4π+4π] intramolecular ph...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0108-2701/small "A [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")
