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Polycationic macrocycles are attractive as they display unique molecular switching capabilities arising from their redox properties. Although diverse polycationic macrocycles have been developed, those based on cationic boron systems remain very limited. We present herein the development of novel polycationic macrocycles by introducing organoboronium moieties into a conjugated organoboron macrocyclic framework. These macrocycles consist of four bipyridylboronium units that are connected by fluorene and either electron‐deficient arylborane or electron‐rich arylamine moieties. Electrochemical studies reveal that the macrocycles undergo reversible multi‐step redox processes with transfer of up to 10 electrons. Switchable electrochromic behavior is demonstrated via spectroelectrochemical studies and the observed color changes are rationalized by correlation with computed electronic transitions using DFT methods.

Polycationic macrocycles are attractive as they display unique molecular switching capabilities arising from their redox properties. Although diverse polycationic macrocycles have been developed, those based on cationic boron systems remain very limited. We present herein the development of novel polycationic macrocycles by introducing organoboronium moieties into a conjugated organoboron macrocyclic framework. These macrocycles consist of four bipyridylboronium units that are connected by fluorene and either electron‐deficient arylborane or electron‐rich arylamine moieties. Electrochemical studies reveal that the macrocycles undergo reversible multi‐step redox processes with transfer of up to 10 electrons. Switchable electrochromic behavior is demonstrated via spectroelectrochemical studies and the observed color changes are rationalized by correlation with computed electronic transitions using DFT methods.

We herein describe a new design principle to achieve B/N‐doped cyclophane where an electron‐donor block of three triarylamines (Ar₃N) and an acceptor block of three triarylboranes (Ar₃B) are spatially separated on opposite sides of the π‐extended ring system. DFT computations revealed the distinct electronic structure of theblock‐type macrocycleMC‐b‐B3N3with a greatly enhanced dipole moment and reduced HOMO–LUMO energy gap in comparison to its analogue with alternating B and N sites,MC‐alt‐B3N3. The unique arrangement of borane acceptor Ar₃B and amine donor Ar₃N components inMC‐b‐B3N3induces exceptionally strong intramolecular charge transfer in the excited state, which is reflected in a largely red‐shifted luminescence at 612 nm in solution. The respective linear open‐chain oligomerL‐b‐B3N3was also synthesized for comparison. Our new approach to donor–acceptor macrocycles offers important fundamental insights and opens up a new avenue to unique optoelectronic materials.

We herein describe a new design principle to achieve B/N‐doped cyclophane where an electron‐donor block of three triarylamines (Ar₃N) and an acceptor block of three triarylboranes (Ar₃B) are spatially separated on opposite sides of the π‐extended ring system. DFT computations revealed the distinct electronic structure of theblock‐type macrocycleMC‐b‐B3N3with a greatly enhanced dipole moment and reduced HOMO–LUMO energy gap in comparison to its analogue with alternating B and N sites,MC‐alt‐B3N3. The unique arrangement of borane acceptor Ar₃B and amine donor Ar₃N components inMC‐b‐B3N3induces exceptionally strong intramolecular charge transfer in the excited state, which is reflected in a largely red‐shifted luminescence at 612 nm in solution. The respective linear open‐chain oligomerL‐b‐B3N3was also synthesized for comparison. Our new approach to donor–acceptor macrocycles offers important fundamental insights and opens up a new avenue to unique optoelectronic materials.