Systems of fused aromatic rings known as acenes are frequently used in organic materials. Heteroacenes (example pictured), containing oxygen or sulfur in particular, are common building blocks. However, the electronic influence of these heteroatoms has not been sufficiently evaluated due to the difficult synthesis of furo- and thienoacenes. In addition to this synthetic challenge, a suitable method to evaluate structure-electronic relationships is also needed.
Jérôme Waser, Clémence Corminboeuf, Swiss Federal Institute of Technology Lausanne (EPFL), and colleagues have developed a protocol to synthesize heterotetracene compounds which have potential applications in organic materials. The researchers used a domino alkynylation-cyclization process with a hypervalent iodine reagent to form the thiophene or furan core.
The thiophene protocol was optimized with gold(III) chloride as the catalyst, whereas the furan procedure worked best with platinum(II) chloride. These products were then cyclized using Pt to obtain the desired heterotetracene structures. In contrast to previously developed procedures, this synthesis worked well for both thieno- and furoacene products, containing either one or two O or S atoms.
The team performed computations on the acenes to assess the hole-mobility properties and corresponding values are equal to or better than those of reported acene-containing organic materials. The results show that hole mobility is highly influenced by both the heteroatom position and its identity (O or S). According to the team, the study could contribute to the improved development of such organic materials.
- Heterotetracenes: Flexible Synthesis and in Silico Assessment of the Hole-Transport Properties,
Yifan Li, Ganna Gryn’ova, Felipe Saenz, Xavier Jeanbourquin, Kevin Sivula, Clémence Corminboeuf, Jérôme Waser,
Chem. Eur. J. 2017.