Design and Short-step Synthesis of π-Conjugated Networks toward n-Type Semiconducting Materials

Abstract

Although a variety of polyaromatic hydrocarbons (PAHs), describing graphene segments containing unsaturated hexagonal rings, exhibit a predominantly electron-rich character, fullerenes with unsaturated hexagonal and pentagonal rings are electron-deficient and can thus be employed as n-type materials. The pyracylene skeleton, a key segment of fullerenes, is particularly interesting due to its antiaromatic character and high electron affinity. We have recently reported short-step synthesis of PAHs that contain a pyracylene moiety, which are based on twofold Scholl cyclization. The thus obtained PAHs exhibit not only an electron-deficient character, but also unique reactivity, which furnished compounds with a curved or planar π-surface and distinct emission behavior in the solid state. During our studies on the synthesis of PAHs, we have discovered a one-pot domino cross-Scholl reaction in which tetracene reacts with six molecules of benzene to form eight C-C bonds. This unprecedented reaction should contribute to the short-step synthesis of luminescence materials with intense excimer-type emission. In addition, n-type organic materials are of paramount importance for the generation of flexible thermoelectric modules. We briefly introduce our synthetic studies toward conductive π-conjugated nickel bis- (dithiolene) complexes to develop solution-processable and air-stable n-type thermoelectric films with improved performance. The results presented here should contribute to the facile synthesis of advanced materials with potential applications in flexible thermoelectric generators.