Semiconducting Self-Assembled Nanofibers Prepared from Photostable Octafluorinated Bisanthene Derivatives

Bisanthene is an important class of small two-dimensional polycyclic aromatic hydrocarbons with a zigzag-edged graphene nanoribbon character. Therefore, the functionalization and deep understanding of the structure-property relationship of bisanthene would provide an effective design for small organic molecular devices. In this study, octa- and tetrafluorinated bisanthene derivatives were synthesized for investigating the effect of electronegative fluorine substitution on the structure and physical property of bisanthene. Firstly, the octafluorinated bisanthene derivative has a twisted structure due to the steric repulsion of fluorine atoms at the bay region. Secondly, the absorption and fluorescence peak maxima are blueshifted with an increase in the degree of fluorine substitution. Notably, a triisopropylsilylethynyl-substituted octafluorinated derivative (F8) exhibited strong fluorescence at 657 nm with high fluorescence quantum yield (84 %). Additionally, cyclic voltammograms indicate the positive effect of fluorine substitution on the high highest occupied molecular orbital energy level of the molecules; thus, F8 molecule exhibited a remarkably increased photostability. Finally, the self-assembled behavior of fluorinated compounds was investigated by scanning electron microscopy and X-ray diffraction analysis. Specifically, F8 self-assembled to form bundles of long semicrystalline nanofibers exhibiting hole-transporting properties (3.4×10^-3  cm²  V^-1  s^-1 ).