Visible‐Light Switchable Rings and Chains in Dynamic Covalent Imine Chemistry

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Abstract The self‐assembliy of red‐light switchable, functionalised ortho‐difluoroazobenzene isomers E‐/Z‐A with aliphatic diamines exhibits an alternating match/mismatch behaviour depending on the diamine's chain length. While even‐numbered diamines exclusively form imine macrocycles with the Z‐configured azobenzene isomer, odd‐numbered diamines form photoswitchable, defined macrocycles. The formation of Z,Z‐A2X2‐type macrocycles was demonstrated with butane‐1,4‐ (B) and hexane‐1,6‐diamine (H), while additionally E,E‐A2X2‐type macrocycles were obtained with propane‐1,3‐ (Pr), pentane‐1,5‐diamine (Pe), and diethylene glycol bisamine (O), validated by single‐crystal X‐ray structures of E,E‐A2Pr2 and E,E‐A2O2. The observed reactivity differences arise from the preferred conformations of the flexible diamines in solution, which alternate predictably with odd and even numbers of methylene groups, investigated by 19F‐DOSY NMR experiments, MALDI‐MS measurements, and UV/Vis spectroscopy. These findings provide detailed insight into photoresponsive self‐assembled systems and highlight the potential of azobenzenes in dynamic covalent chemistry, offering new opportunities for controlling structure and function in adaptive materials.

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