Structure determination of thiacyanine dye J-aggregates in thin films:Comparison between spectroscopy and wide angle X-ray scattering

摘要

The structural properties of J-aggregates in thin films were studied by wide-angle synchrotron X-ray scattering,UV/V1S absorption and fluorescence spectroscopy and time-correlated single photon counting.The system of investigation was the cyanine dye (C_(33)H_(32)N_2O_6~-oHN(CH_2CH_3)_3~-;2-{3-[l-(3-sulfopropyl)-naphtho-[1,2-d]thiazol-2(lH)-yliden]-2-ethyl-l-propen-l-yl}-l-(3-sulfo-propyl)-naphtho-[l,2-d] thiazolium-betain-triethylammonium salt) incorporated into a Na-polystyrene-sulfonate (PSSNa) matrix.It could be shown that,depending on the preparation conditions,it is possible to create either a monomer phase or a J-aggregate phase in PSSNa films.Both could optically be distinguished through their typical bathochromic shift of the J-aggregate band in the UV/VIS spectra.Wide angle X-ray scattering experiments confirm intermolecular distances of 7 A in the J-aggregate and an angle of inclination of 20deg.Out of optical studies,the angle of inclination was determined to be around 30deg.A more detailed interpretation of the wide angle X-ray scattering signals suggests that 80% of the formed J-aggregate consists of dimers and 20% of a helical arrangement with a diameter of ca.16 A.The used stacking model was built out of mono-m conformer units which were confirmed to be the most stable conformation by DFT calculations (6-31G basis set,BeckeLyp functional).