Gaebert Carsten, Mattay Jochen, Toubartz Marion, Steenken Steen, Müller Beat, Bally Thomas
Fakultät für Chemie, Universität Bielefeld, 33501 Bielefeld, Germany.
Chemistry. 2005 Feb 4;11(4):1294-304. doi: 10.1002/chem.200400557.
Radical cations were generated from different phenyl-substituted aziridines by pulse radiolysis in aqueous solution containing TlOH.+, N3. or SO4.- as oxidants or in n-butyl chloride, by 60Co gamma radiolysis in Freon matrices at 77 K, and in some cases by flash photolysis in aqueous solution. Depending on the substitution pattern of the aziridines, two different types of radical cations are formed: if the N atom carries a phenyl ring, the aziridine appears to retain its structure after oxidation and the resulting radical cation shows an intense band at 440-480 nm, similar to that of the radical cation of dimethylaniline. Conversely, if the N atom carries an alkyl substituent while a phenyl ring is attached to a C-atom of the aziridine, oxidation results in spontaneous ring opening to yield azomethine ylide radical cations which have broad absorptions in the 500-800 nm range. In aqueous solution the two types of radical cations are quenched by O2 with different rates, whereas in n-butyl chloride, the ring-closed aziridine radical cations are not quenchable by O2. The results of quantum chemical calculations confirm the assignment of these species and allow to rationalize the different effects that phenyl rings have if they are attached in different positions of aziridines. In the pulse radiolysis experiments in aqueous solution, the primary oxidants can also be observed, whereas in n-butyl chloride a transient at 325 nm remains unidentified. In the laser flash experiments, both types of radical cations were also observed.
在含有TlOH⁺、N₃⁻或SO₄²⁻作为氧化剂的水溶液中，通过脉冲辐解，或在正丁基氯中，通过77 K下氟利昂基质中的⁶⁰Coγ辐解，以及在某些情况下通过水溶液中的闪光光解，由不同苯基取代的氮丙啶产生自由基阳离子。根据氮丙啶的取代模式，会形成两种不同类型的自由基阳离子：如果氮原子带有一个苯环，氮丙啶在氧化后似乎保留其结构，并且产生的自由基阳离子在440 - 480 nm处显示出强吸收带，类似于二甲基苯胺的自由基阳离子。相反，如果氮原子带有一个烷基取代基，而一个苯环连接到氮丙啶的一个碳原子上，氧化会导致自发开环，产生在500 - 800 nm范围内具有宽吸收的氮杂甲亚胺叶立德自由基阳离子。在水溶液中，这两种类型的自由基阳离子被O₂以不同的速率猝灭，而在正丁基氯中，闭环的氮丙啶自由基阳离子不能被O₂猝灭。量子化学计算结果证实了这些物种的归属，并有助于解释苯环连接在氮丙啶不同位置时产生的不同影响。在水溶液中的脉冲辐解实验中，也可以观察到初级氧化剂，而在正丁基氯中，325 nm处的一个瞬态仍然无法确定其身份。在激光闪光实验中，也观察到了两种类型的自由基阳离子。
