Einelektronen‐Redoxreaktionen von 4‐(1‐Pyridinio)phenolat‐Betain: ESR/ENDOR‐Charakterisierung seiner Radikalionen und ‘Batterie‐Effekt’

One‐Electron Redox Reactions of 4‐(1‐Pyridinio)phenolate Betaine: ESR/ENDOR Characterization of its Radical Ions and ‘Battery Effect’ Blue zwitterionic 2,6‐Di( tert ‐butyl)‐4‐(2,4,6‐triphenyl‐1‐pyridinio)phenolate 1a can be reduced to its blue‐green radical anion \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{- \atop \dot{}}$\end{document} using alkaline metals, and oxidized to its colorless radical cation 1 by Ag(OOCCF 3 ) or electrochemically. ESR/ENDOR spectra of their aprotic THF solutions indicate predominant spin population either in the pyridinium ( \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1a}^{- \atop \dot{}}$\end{document} ) or in the phenolate ring ( \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1a}^{+ \atop \dot{}}$\end{document} ). Reduction with other alkaline metals Li, Na, or Cs yields no changes in the ESR/ENDOR signal patterns, i.e. provides no indication of radical ion pair formation. The cyclovoltammetrically determined first reduction and oxidation potentials at −1.11 V and +0.26 V, respectively, are both reversible and, in principle, allow to construct a molecular battery.