Acenes Generated from Precursors and Their Semiconducting Properties

Abstract

Acenes are a class of aromatic hydrocarbons composed of linearly fused benzene rings. Noteworthy features of these molecules include their extended flat structure and the narrow gap between the HOMO and LUMO energy levels. However, the preparation of larger acenes, those that are larger than pentacene, has been challenging. These molecules are relatively unstable and have low solubility in typical solvents. Recently researchers have developed a new synthesis route for higher acenes using stable and soluble "precursors," which generate these structures on demand by either heating or irradiation of light. Using this method, nonsubstituted hexacene, heptacene, octacene, and nonacene were successfully prepared. In this Account, we summarize the preparation of nonsubstituted acenes from corresponding precursors, describe their physical properties, and discuss potential applications including potential usage in organic semiconductor devices. We first introduced the concept of using a precursor in the work with pentacene. Overall, we divide this methodology into two categories: masking pentacene itself with a dienophile to form a cycloadduct and the construction of higher acenes through conventional synthetic procedures. For the first category, a diverse array of dienophiles could be chosen, depending on the processing needs, especially for use in field-effect transistors (FETs). For the second category, researchers synthesized the pentacene precursor molecules using a multistep procedure. Upon proper activation, these molecules expel small fragments to generate pentacene readily. This strategy enabled the production of pentacene andunprepared higher acenes ranging from hexacene to nonacene. This new method provides a way to unravel the fascinating chemistry of higher acenes.

Preparation of a Key Tetraene Precursor for the Synthesis of Long Acenes

“…As an example of the use of 1 in the straightforward preparation of long acenes, 6,13‐dihydro‐6,13‐methanopentacen‐15‐one ( 12 ) can be prepared in 2 steps starting from 1 (Scheme ), following the route described in Scheme . Compound 12 has been described as a new type of soluble pentacene precursor for organic thin‐film transistors , . Pentacene films were obtained by spin‐coating of stable and soluble 12 , evaporation of the solvent and decarbonylation.…”

Hexacene: Synthesis, Properties and Future Perspectives

“…Dealing with the problem of low solubility is therefore another issue that needs to be solved while using pentacene. [1] The next higher acene is hexacene, whose synthesis was first reported by Clar in 1942. [2] Plate-shaped bluish-green crystals were obtained through vacuum sublimation, and their identity was confirmed by spectral analyses.…”

Environmental effects on the charge transfer properties of Graphene quantum dot based interfaces

“…Yet, this CT can be strongly reduced by dynamic disorder (ie, thermal fluctuations) and the presence of an environment which can strongly alter the transfer ability of the device, which is for instance found to be of importance for the electron transfer in biomolecular systems and DNA . Hence, research has been focused on the design and synthesis of novel aromatic and conjugated organic materials which can efficiently transfer charges at the interface, to obtain high charge transfer ability …”