Macrocycles which can form highly ordered architectures through self-organization represent intriguing building blocks in supramolecular chemistry. Numerous systems have fascinated chemists in this regard as such as cucurbitrils, cyclodextrins, calixarenes, pillarenes, asararenes and several other scaffolds, including macrocycles incorporating redox active paraquat units. Here we introduce a ‘triangular’ cyclophane, cyclotris(paraquat-p-phenylene) hexafluorophosphate (1), which incorporates three paraquat units, linked together by phenylene groups, and its methoxy-substituted analog, cyclotris(paraquat-p-2,5-dimethoxyphenylene) hexafluorophosphate (2), in which the phenylene pillars are replaced by electron-rich dimethoxyphenylene units. These cyclophanes are prepared via a facile 3 step synthesis and studies of their photochemistry, electrochemistry and solid-state properties are presented. 2 gives rise to C3-symmetric cyclophanes which self-organize into a highly ordered superstructure bearing nanometer-scale channels. Such porosity is not observed for 1, which presents a much less uniform crystal structure, highlighting the impact of the dimethoxyphenylene pillars on dictating a well-defined superstructure. 2 is also reduced to its trisradical tricationic form and recrystallized to explore the effect of radical-radical interactions on its packing in the solid state. Currently we consider these cyclic paraquat trimers as a great opportunity to expand the scope of paraquat incorporating cyclophanes and envision them as a fruitful entry point towards the fabrication of larger systems such as tubular or advanced mechanically interlocked molecular architectures.

Cyclic paraquat trimers

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.