Author/Authors :
Le Breton، نويسنده , , H. and Létard، نويسنده , , R. Lapouyade، نويسنده , , R. and Le Calvez، نويسنده , , A. and Maleck Rassoul، نويسنده , , R. and Freysz، نويسنده , , E. and Ducasse، نويسنده , , A. and Belin-Ferré، نويسنده , , C. and Morand، نويسنده , , J.-P.، نويسنده ,
Abstract :
We have prepared Langmuir-Blodgett films of 4′-N,N-dimethylamino-4ʹ-heptadecafluorooctylsulfonyl stilbene (PFSDS) and its bridged derivatives PFSDS-N34 and PFSDS-023, where the central double bond is rigidly bridged by a heteroatom. We have characterized their organization by Fourier transform infrared spectroscopy (FTIR) electronic absorption spectroscopy and second harmonic generation SHG studies. The observed changes in absorption and emission spectra of the LB films can be explained by an exciton model, applied to H-aggregates with a strong Coulombic destabilization of the excited state and an additional specific interaction in PFSDS-N34. The second harmonic generation measurement from surface setup leads to the second-order molecular hyperpolarizability (β ≈ 2 x 10−28 esu) of these molecules in LB films. Bridging the double bond of the stilbenes in a five-membered ring with an oxygen or nitrogen atom comes out to be an efficient molecular design to avoid photochemical processes and thus to increase the damage threshold.
