MOREAU, C.; SEREIN-SPIRAU, F.; LETARD, J. F.; LAPOUYADE, R.; JONUSAUSKAS, Gediminas; RULLIERE, C.

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MOREAU, C.
Laboratoire de chimie organique et organométallique [LCOO]

SEREIN-SPIRAU, F.
Laboratoire de chimie organique et organométallique [LCOO]

LETARD, J. F.
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

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Ce document a été publié dans

Journal of Physical Chemistry B. 1998-02-26, vol. 102, n° 9, p. 1487-1497

American Chemical Society

Résumé en anglais

A new series of oligomers for nonlinear optics (NLO), the thiophene−dimethylsilyl co-oligomers, (TSi)n−T with n = 1−3, have been synthesized in order to combine third-order NLO response and transparency in the visible region. Stationary-state absorption spectra, fluorescence spectra, and time-resolved absorption (picosecond) have been carried out. In sharp contrast with oligothiophenes, the absorption spectra of (TSi)n−T are not red-shifted as n increases, but as for short oligothiophenes their quantum yield of fluorescence is low because of the competitive triplet-state formation and their emission wavelength range is remarkably solvent-independent. These data show slight increase of the dipole moment between the S0 ground state and the S1 excited state, in agreement with theoretical calculations (ZINDO method). Fast intersystem crossing is observed between singlet and triplet states and S1 → Sn and T1 → Tn spectra have been measured. Optical nonlinearity (γ) of the excited state has been measured and compared to the terthiophene. The large molecular second hyperpolarizability of the silyl derivatives associated with their interesting transparency properties shows that such oligomers may be considered, in the excited state, as promising molecules for nonlinear applications.< Réduire

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Laboratoire Ondes et Matière d'Aquitaine (LOMA) - UMR 5798