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Free, publicly-accessible full text available August 31, 2024
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Abstract Exciton and charge delocalization across π‐stacked assemblies is of importance in biological systems and functional polymeric materials. To examine the requirements for exciton and hole stabilization, cofacial bifluorene (
F 2) torsionomers were designed, synthesized, and characterized: unhindered (model)MeF 2, sterically hinderedtBuF 2, and cyclophane‐likeCF 2, where fluorenes are locked in a perfect sandwich orientation via two methylene linkers. This set of bichromophores with varied torsional rigidity and orbital overlap shows that exciton stabilization requires a perfect sandwich‐like arrangement, as seen by strong excimeric‐like emission only inCF 2 andMeF 2. In contrast, hole delocalization is less geometrically restrictive and occurs even in sterically hinderedtBuF 2, as judged by 160 mV hole stabilization and a near‐IR band in the spectrum of its cation radical. These findings underscore the diverse requirements for charge and energy delocalization across π‐stacked assemblies. -
Abstract Exciton and charge delocalization across π‐stacked assemblies is of importance in biological systems and functional polymeric materials. To examine the requirements for exciton and hole stabilization, cofacial bifluorene (
F 2) torsionomers were designed, synthesized, and characterized: unhindered (model)MeF 2, sterically hinderedtBuF 2, and cyclophane‐likeCF 2, where fluorenes are locked in a perfect sandwich orientation via two methylene linkers. This set of bichromophores with varied torsional rigidity and orbital overlap shows that exciton stabilization requires a perfect sandwich‐like arrangement, as seen by strong excimeric‐like emission only inCF 2 andMeF 2. In contrast, hole delocalization is less geometrically restrictive and occurs even in sterically hinderedtBuF 2, as judged by 160 mV hole stabilization and a near‐IR band in the spectrum of its cation radical. These findings underscore the diverse requirements for charge and energy delocalization across π‐stacked assemblies.