Synthesis and post-cyclisation modification of conjugated macrocycles

Abstract

π-Conjugated macrocycles are emerging as an exciting class of organic molecules and finding their way into various state-of-the-art applications in organic electronics, owing to their unique optical and electronic properties. Demonstrating highly tunable redox-activity, an infinitely π-conjugated framework and an intrinsically porous structure in solid state, these materials are particularly promising as candidates for organic secondary batteries. In the course of this work, various macrocycles with different conjugated linkers constructed through facile one-step cyclooligomerisation reactions were obtained. The structural motif of the prepared macrocycles was based on the previously reported [2.2.2.2]paracyclophane-1,9,17,25-tetraene (PCT), a paracyclophane consisting of four phenylene rings connected by four vinylene linkers, which is accessible via a facile one-step Wittig reaction. The synthetic procedure was optimised and the compound analysed in regard to its applicability in organic secondary batteries. In an approach to find a more scalable procedure, an alternative synthetic route via a benzoin condensation starting from cheap and easily available terephthalaldehyde was tested. Furthermore, a systematic strategy for designing active materials for battery application by introducing carbonyl groups on the macrocycle's perimeter was constructed. For this, an effcient synthesis for the preparation of macrocycles incorporating four maleic anhydride units instead of the vinylene linkers via a Perkin-type cyclisation reaction was developed. This versatile building block allowed for post-cyclisation modification of the functional groups, hence the preparation of a family of N-alkylated imide and a sodium carboxylated macrocycles to further tune the material's optoelectronic properties. The so obtained π-conjugated macrocycles were investigated for their optical, thermal and electronic properties and found to show promising characteristics suitable for application in organic electronic materials.