Synthesis of fluorinated anti-fluorenacenedione and the structural, electronic, and field-effect properties

Fluorinated anti-fluorenacenedione 6 was newly synthesized by oxidation of a dehydro[12]annulene fused with tetrafluorobenzene 4. X-Ray crystallography of 6 demonstrated a totally planar structure and shorter intramolecular distances for F ... I, F ... O, and I ... O than the corresponding sums of van der Waals (vdW) radii. In the packing structure, molecules are arranged in a pi-stacked motif, and the intermolecular distances between heavy atoms (C ... I, C ... F, C ... O, F ... I, and F ... O) of the adjacent columns are also shorter than the corresponding sums of vdW radii, indicating highly dense packing for the crystal structure of 6. In the 19F NMR spectrum of 6, a signal for the fluorine atom adjacent to iodine exhibited downfield shift by 29-40 ppm as compared with the other three signals. This is attributed to the intramolecular short contact between F and I atoms, which is supposed to cause a donor-acceptor interaction. Cyclic voltammetry of 6 exhibited two reversible reduction waves at E1/2 = -0.91 and -1.45 V vs. Fc/Fc+. A thin film of 6 was prepared by vacuum deposition and was applied to a field-effect transistor (FET) device, which exhibited n-type transistor responses although the mobility was not very high.