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π-Extended Dihydrophenazines with Three-State NIR Electrochromism Involving Large Conformational Changes
Juri Nagasaki1, Satoru Hiroto1, Hiroshi Shinokubo1
1Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8603, Japan.
Abstract:
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.
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