Conjugated macrocycles of phenanthrene: a new segment of [6,6]-carbon nanotube and solution-processed organic semiconductors

Conjugated macrocycles can be equipped with interesting functions by having polycyclic aromatic hydrocarbon (PAH) building blocks that are larger than benzene. The building block explored herein is phenanthrene, which is connected with varied linkers leading to new trimeric conjugated macrocycles (1-4). The coronal macrocycle 1, whose pi-backbone is a new segment of [6,6]-carbon nanotube, is synthesized from the flat macrocycle 2 by Lewis acid-catalyzed [4 + 2] benzannulation. This suggests a new strategy to synthesize p-extended nanorings from conjugated macrocycles that are more easily accessed. As found from a comparative study with focus on self-assembly and organic semiconductor behavior, flat or nearly flat conjugated macrocycles 2-4 function as p-type organic semiconductors in solution-processed thin film transistors. Their field effect mobility as measured from as-cast films is dependent on their ability of self-aggregation in solution.