TwoStep Redox Systems XIIIl). -Bipyridylium, Bipyrylium, and Bithiopyrylium SaltsThe syntheses of the redox systems N I-N 3, 0 1-0 3, and S 1-S 3 are described. All three exist in three oxidation levels (Red, Sem and Ox) the majority of which could be isolated. Moreover, a useful synthesis of unsymmetrically substituted 4,4'-bipyridyls is reported. While the electronic spectra of Red and Ox are similar, Sem always displays typical bands at longer wavelengths (N, 0, S) dependent on oc-substituents (H; CH3; CsH5). All systems display two reversible one-electron transfers with Ksem 103-106. While systems 0 and S behave very similarly, N shows much more negative potentials. Olsem. BF4-dimerizes reversibly in methylene chloride at higher concentrations.
A ZielsetzungDie Mitteilungen der vorliegenden Reihe befassen sich mit zweistufigen Redoxsystemen der allgemeinen Struktur A, der bereits E. Weitz6) durch seine bahnbrechenden, aber unbeachteten Versuche und Interpretationen sehr nahegekommen ist. In diesen Systemen A sind die Oxidationsstufen Red, Sem, Ox durch reversible Einelektronenubergange verbunden.
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