Structural Characterization of Langmuir-Blodgett Films of a Bridged Polar Stilbene: 2-(4'-((Perfluorooctyl)- sulfonyl)phenyl)-6-(N,N-dimethylamino)benzofuran

The spectral properties of a bridged polar stilbene, the 2-(4'-((perfluorooctyl)sulfonyl)phenyl)-6-(N,N-dimethylamino)benzofuran (PFSDS-O23(dagger)) were investigated in mono- and multilayer Langmuir-Blodgett (LB) films. This molecule forms stable films at the air-water interface which can be transferred to give quartz-supported mono- or multilayers. Absorption and emission spectra of the LB film were compared with those in solution. The dependence of the Stokes shift versus the solvent polarity has been measured to evaluate the extent of charge transfer in the excited state. The observed changes in absorption and emission spectra of the LB films can be explained by an exciton model. The tendency of PFSDS-O23 to form H-aggregates was observed even when diluted with C8F17(CH2)(10)CH2OH (1:18). The molecular cross sectional area and the Fourier transform infrared spectroscopy (FTIR) suggest a perpendicular orientation of the dimethylanilino and perfluoroalkyl groups with respect to the substrate.