Polarity effects on the photophysics of dendrimers with an oligophenylenevinylene core and peripheral fullerene units
Por:
Gutierrez-Nava M., Accorsi G., Masson P., Armaroli N., Nierengarten J.-F.
Publicada:
1 ene 2004
Resumen:
Highly soluble dendritic branches with fullerene subunits at the periphery and a carboxylic acid function at the focal point have been prepared by a convergent approach. They have been attached to an oligophenylenevinylene (OPV) core bearing two alcohol functions to yield dendrimers with two, four or eight peripheral C60 groups. Their photophysical properties have been systematically investigated in solvents of increasing polarity; that is, toluene, dichloromethane, and ben6 zonitrile. Ultrafast OPV? 60 singlet energy transfer takes place for the whole series of dendrimers, whatever the solvent. Electron transfer from the fullerene singlet is thermodynamically allowed in CH2Cl2 and benzonitrile, but not in apolar toluene. For a given solvent, the extent of electron transfer, signaled by the quenching of the fullerene fluorescence, is not the same along the series, despite the fact that identical electron transfer partners are present. By increasing the dendrimer size, electron transfer is progressively more difficult due to isolation of the central OPV core by the dendritic branches, which hampers solvent induced stabilization of charge separated couples. Compact structures of the hydrophobic dendrimers are favored in solvents of higher polarity. These structural effects are also able to rationalize the unexpected trends in singlet oxygen sensitization yields.
Filiaciones:
Gutierrez-Nava M.:
Inst. Phys. Chim. Mat. de Strasbourg, Univ. Louis Pasteur et CNRS, 23 rue du Loess, 67037 Strasbourg, France
Accorsi G.:
Inst. Sintesi Organ. Fotoreattivita, Laboratorio di Fotochimica, Cons. Nazionale Delle Ricerche CNR, Via Gobetti 101, 40129 Bologna, Italy
Masson P.:
Inst. Phys. Chim. Mat. de Strasbourg, Univ. Louis Pasteur et CNRS, 23 rue du Loess, 67037 Strasbourg, France
Armaroli N.:
Inst. Sintesi Organ. Fotoreattivita, Laboratorio di Fotochimica, Cons. Nazionale Delle Ricerche CNR, Via Gobetti 101, 40129 Bologna, Italy
Nierengarten J.-F.:
Inst. Phys. Chim. Mat. de Strasbourg, Univ. Louis Pasteur et CNRS, 23 rue du Loess, 67037 Strasbourg, France
Grp. Chim. Fullerenes Syst. C., Ecl. Europeenne Chim., Polymeres M., Univ. Louis Pasteur et CNRS, 25 rue Becquerel, 67087 Strasbourg Cedex 2, France
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