Highly efficient solid-state red fluorophores using ESIPT: Crystal packing and fluorescence properties of alkoxy-substituted dibenzothiazolylphenols

Ken Ichi Sakai, Hiroshi Kawamura, Noriyuki Kobayashi, Takaaki Ishikawa, Chiori Ikeda, Takemitsu Kikuchi, Tomoyuki Akutagawa

    Research output: Contribution to journalArticlepeer-review

    38 Citations (Scopus)

    Abstract

    An excited-state intramolecular proton transfer (ESIPT) fluorophore, 2,6-bis(benzothiazol-2-yl)phenol, was modified with alkoxy groups at the 4-position to obtain the methoxy (OMe), ethoxy (OEt), propoxy (OPr), and butoxy (OBt) derivatives. The derivatives exhibit bright red fluorescence in chloroform, giving the same fluorescence spectra with a maximum (λmax) at 619 nm. However, in the crystalline state, the λmax values of OMe and OEt are bathochromically shifted, producing a deeper red color, whereas those of OPr and OBt are hypsochromically shifted producing an orange color. X-ray analysis of the OMe and OPr crystals shows that OMe molecules interact strongly with each other through sulfur-sulfur contacts, whereas the OPr molecules are stacked in an eclipsed arrangement. Assuming that the OMe and OPr crystals are J- and H-aggregates, respectively, the difference in solid-state fluorescence could be explained by the Davydov exciton coupling theory. The OEt derivative was the best solid-state red fluorophore (λmax = 633 nm) with a fluorescence quantum yield of 0.32. Therefore, ESIPT fluorophores are promising for developing a highly efficient solid-state red-emitting material with relatively small π-conjugation and no bulky groups.

    Original languageEnglish
    Pages (from-to)3180-3185
    Number of pages6
    JournalCrystEngComm
    Volume16
    Issue number15
    DOIs
    Publication statusPublished - 2014 Apr 21

    ASJC Scopus subject areas

    • Chemistry(all)
    • Materials Science(all)
    • Condensed Matter Physics

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