Synthesis of 5,7,12,14-Tetraarylpentacenes from Pentacene-5,7,12,14-tetrone and Characterisation of the Tetrol Intermediates

Pentacene has excellent semi-conducting properties but its practical use in organic thin-film transistors (OTFTs) has some drawbacks caused by its sensitivity to oxygen and low solubility. In order to overcome these problems one can introduce substituents on the ring system. In this context, we are investigating the possibility of introduction of aryl substituents on the pentacene backbone. 5,7,12,14-Tetraaryl-substituted pentacenes are described in this article. They have been prepared from the 5,7,12,14-aryl-substituted pentacene-5ʹ,7ʹ,12ʹ,14ʹ-tetrol. We isolated all isomers of the tetrol. We also found that the 5,7,12,14-thienylpentacene5ʹ,7ʹ,12ʹ,14ʹ-tetrol can undergo rearrangement to afford both 5,5ʹ,7,7ʹ-tetrathi­enylpentacene-12,14-one and 5,5ʹ,12,12ʹ-tetrathienylpentacene-7,14-one.