Cross-Conjugated Nanoarchitectures

This project was focused on shape-persistent macrocycles featuring cross-conjugated subunits, for long term applications in organic photovoltaics and single-molecule devices. The proposed compounds allow the study of charge-transfer within single molecules mediated by pairs of conjugated bridges, a two dimensional pi-system design that had been unexplored. A synthetic method was developed allowing several series of these compounds to be prepared. As expected, charge-transfer through cross-conjugated meta-phenylene bridges was found to be slow compared to linearly conjugated 2,5-thiophene-based reference compounds. Unexpectedly, however, the pairing of bridges was found to greatly reduce electronic coupling regardless of their specific nature. As modulation of the electronic coupling can be exploited in the creation of single-molecule devices (e.g., transistors), this macrocyclic design strategy may be of use in future applications. The design of columnar materials based on these motifs was also explored. While liquid crystal phases (the original target) were not observed, solution-phase columnar self-assembly of oblong macrocycles was studied and strategies for the determination of the stacking geometry using computational chemistry were developed.
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