Electron- or hole-transporting nature selected by side-chain-directed π-stacking geometry: liquid crystalline fused...

Novel liquid crystalline (LC) semiconductors were prepared from the copper complex of a fused porphyrin dimer as the electroactive core by attaching to its periphery dodecyl and semifluoroalkyl side chains site-specifically (P≡P(hetero)) and semifluoroalkyl side chains alone (P≡P(homo)). The former and latter formed rectangular columnar and orthorhombic LC mesophases, respectively, where the stacking geometries of the π-conjugated core are quite different from one another. Although the π-electronic properties of the core units in P≡P(hetero) and P≡P(homo) in solution are substantially identical to one another, transient photocurrent profiles of their LC states under time-of-flight conditions clearly showed that P≡P(hetero) behaves as an n-type semiconductor, whereas P≡P(homo), in contrast, behaves as a p-type semiconductor.