π-Extended dihydrophenazines were successfully prepared by oxidation of 2-(N-arylamino)anthracenes. Their roof-type conformations were revealed by X-ray diffraction analysis, and the analysis of the optical properties indicated the presence of intramolecular charge-transfer processes. Upon chemical oxidation, the electronic absorption dramatically changed in a two-step fashion. The electron spin resonance (ESR) analysis revealed that, depending on the amount of oxidant added, either a paramagnetic radical cation or a diamagnetic dication was generated. The NMR analysis revealed a conformational change upon oxidation, which was supported by theoretical calculations. A three-state electrochromic behavior was observed during the electrochemical oxidation and reduction cycles, showing sequential switching between visible and near-infrared (NIR) absorption properties upon application of electrochemical stimuli.
Getting a piece of the pie: A synthesis of π‐extended dihydrophenazines based on anthracenes has been developed. Their charge‐transfer characteristic and roof‐type structures were determined. They exhibited dynamic motion, like butterfly flapping its wings, by chemical oxidation. Upon oxidation, the absorption was changed in three stages, resulting in intense bands in the near IR region, owing to reversal of a charge‐transfer process. Similar phenomena were also observed by electrochemical stimuli. More information can be found in the Full Paper by Juri Nagasaki, Satoru Hiroto and Hiroshi Shinokubo on page 2311 in Issue 1, 2017 (DOI: 10.1002/asia.201700840).
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