Abstract: In-situ synchrotron X-ray diffraction and far-IR spectra of DPP-11{2,5-bis[11-(1-pyridinium)alkyl]-3,6-bis(2-thienyl)-1,4-dioxopyrrolo[3,4-c]pyrrole ditosylate salts} and its micelles in aqueous solution were studied. Although X-ray studies show no indication of phase transition, however, the π-π interactions become stronger with increasing pressure which can be deduced from far-IR spectra. A new far-IR absorption peak is found to be related to the π-conjugated aromatic dyes in DPP-11 micelles. Upon increasing pressure, the peak shifted toward higher wavenumber region due to the stronger π-π interactions.

Key words: High pressure, 2,5-Bis[11-(1-pyridinium)alkyl]-3,6-bis(2-thienyl)-1,4-dioxopyrrolo[3,4-c]pyrrole ditosylate salts(DPP-11), π-π Interaction, Synchrotron radiation, Far-IR spectrum