π-π interactions in DPP-11 supramolecular micellar aggregates under high-pressure

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 pi-pi 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 7r-conjugated aromatic dyes in DPP-11 nucelles. Upon increasing pressure the peak shifted toward higher wavenumber region due to the stronger Ir-Ir interactions.