Synthesis of Pyrene-Substituted Azobenzene Derivatives and Their Assembly into Flat Structures for Stimuli-Induced Switching

We report the design of pyrene-substituted azobenzene chromophores and their assembly into flat aggregates capable of repeated switching of their absorption and emission properties in response to light and heat. The introduction of a relatively longer butoxy linker between the pyrene and azobenzene (AzBuPy) resulted in the production of more than 90% of cis-azobenzene at the photostationary state of ultraviolet (UV) light, as determined by UV-visible absorption and 1H NMR spectral data. Flat petal-shaped micrometer-sized structures formed in highly polar DMF-H2O mixtures did not experience severe disassembly even after sufficient UV light irradiation, and showed excellent photoswitching performance. In addition, we investigated light and heat responses of DPA@AzBuPy aggregates assembled from hydrophobic fluorophore (9,10-diphenylanthracene: DPA) and AzBuPy mixtures.