Staggarenes - A New Family of Extended Aromatic Systems Based on Fused Anthracenes

Abstract

The overall objective of this project is to synthesise and design unique new extended aromatic structures assembling fundamental three-ring aromatic units (anthracenes) iteratively into more complex arrangements. In particular, we aim to annulate more than two functionalized anthracene cores together in a stepwise manner by extending the conjugation of the π-system via a Suzuki coupling reaction and Scholl reaction. The targeted materials may be recognized as a structural fragment of graphene and we term them "staggarenes". Indeed, the annulation of anthracene units in a lateral position is an appealing target; the stepwise staggared extension of the π-conjugated systems laterally suggests a structure that is likely to be a stable candidate for optoelectronics. However, the target molecule can be synthetically challenging due to the need for stepwise procedures including the preparation of functionalized anthracene components. Unsubstituted/ substituted bianthracenes have been constructed by the palladium- catalyzed Suzuki cross-coupling reaction using unsubstituted/ substituted 9-anthracenyl (pinacol) boronate ester and iodoanthracene partners. Extension of the π-conjugated system of several anthracene fused anthracene (AFA) derivatives has been designed to investigate their reactivity under Scholl oxidative cyclodehydrogenation reaction conditions. These novel precursors have been successfully characterized using NMR spectroscopy, MALDI-TOF MS, single-crystal X-ray diffraction, UV–vis, and emission spectroscopy.