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The Role of Torsional Dynamics on Hole and Exciton Stabilization in π‐Stacked Assemblies: Design of Rigid Torsionomers of a Cofacial Bifluorene
Author(s) -
Wang Denan,
Ivanov Maxim V.,
Kokkin Damian,
Loman John,
Cai JinZhe,
Reid Scott A.,
Rathore Rajendra
Publication year - 2018
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201804337
Subject(s) - delocalized electron , steric effects , exciton , chemical physics , structural rigidity , electron delocalization , materials science , rigidity (electromagnetism) , charge (physics) , chemistry , molecular physics , crystallography , photochemistry , physics , condensed matter physics , stereochemistry , quantum mechanics , geometry , mathematics , organic chemistry , composite material
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) Me F 2, sterically hindered tBu F 2, and cyclophane‐like C F 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 in C F 2 and Me F 2. In contrast, hole delocalization is less geometrically restrictive and occurs even in sterically hindered tBu F 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.