Carrier transport and mesomorphic properties of deformable fluorinated perylene bisimide bearing disiloxane chains

We synthesized liquid crystalline difluorinated perylene bisimide derivatives bearing oligosiloxane moieties. At room temperature, these compounds exhibited columnar phases which were stabilized thermodynamically, compared to that of a non-fluorinated analog. The absorption bands in the thin films of the fluorinated compounds exhibited a slight bathochromic shift compared to that in the solution state, indicating a weak electronic coupling between the fluorinated perylene bisimide cores in the columnar phases. The electron mobilities in the columnar phases of the difluorinated compounds were determined to be on the order of 10 -2 cm 2 V - 1 s - 1 at room temperature by the time-of-flight measurements. The LUMO levels of the difluorinated compounds were lowered by 0.1 eV from that of non-fluorinated analog. Anion radicals of the fluorinated compounds were stable as that of the non-fluorinated analog while dianions of the fluorinated compounds were unstable unlike that of the nonfluorinated analog. The difluorinated compounds was soft waxy solid. In particular, the 1,7-difluorinated derivative is deformable to form various shapes at room temperature. A study on the surface morphology of the thin film indicated formation of microscopic grooves, which should enhance the softness of the compound.