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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Genuine Pyrimidine Radical Cations Generated by Radiation-Induced Electron Transfer to Butyl Chloride or Acetone Parent Ions
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Genuine Pyrimidine Radical Cations Generated by Radiation-Induced Electron Transfer to Butyl Chloride or Acetone Parent Ions

机译：辐射诱导的电子转移至丁基氯或丙酮母体离子产生的真正嘧啶自由基阳离子

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摘要

Radical cations of multiple methylated uracils and thymines were generated by electron transfer to parent ions of solvents of low polarity such as n-butyl chloride and acetone. Pulse radiolysis resulted in the transient optical absorption spectra of the pyrimidine radical cations (Py~+) which exhibit bands generally peaking around #lambda#=400 nm and in acetone showing an additional band in the range of #lambda#_(max) = 500-560 nm. The identification of the solute radical cations is based on the direct observation of the formation of Py~(.+) by electron transfer (k = (1-2) * 10~(10) M~(-1)S~(-1)), the nucleophilic reaction with the counterion (e.g., Cl~-), the relatively low reactivity with oxygen even for the fully methylated nitrogen groups (k < 2 * 10~8 M~(-1)S~(-1)), and the observation of a subsequent electron transfer from triphenylamine to the pyrimidine radical cations proceeding in a diffusion-controlled manner. The solvent dependence of the spectral shape of Py~(.+) was also studied in acetone-butyl chloride mixtures and was found to depend on the polarity of the surroundings. This phenomenon is explained in terms of a lactam-lactim-like tautomerism of the transient involving the whole plane molecule. Quantum chemical calculations support the experimental findings by explaining the spectral structure and enable the formulation of the lactims as either 1,4- or 3,4-localized.
机译：多种甲基化尿嘧啶和胸腺嘧啶的自由基阳离子是通过电子转移至低极性溶剂（如正丁基氯和丙酮）的母体离子而生成的。脉冲辐射分解导致嘧啶自由基阳离子（Py〜+）的瞬态光吸收光谱，该光谱通常在＃lambda＃= 400 nm附近出现谱带峰，而在丙酮中则显示出在#lambda #_（max）=范围内的附加谱带。 500-560 nm。溶质自由基阳离子的鉴定是基于通过电子转移直接形成Py〜（。+）（k =（1-2）* 10〜（10）M〜（-1）S〜（- 1）），与抗衡离子（例如Cl〜-）的亲核反应，甚至与完全甲基化的氮基团（k <2 * 10〜8 M〜（-1）S〜（-1 ）），然后观察到电子从三苯胺向嘧啶自由基阳离子的转移是以扩散控制的方式进行的。在丙酮/正丁基氯的混合物中还研究了Py〜（。+）光谱形状对溶剂的依赖性，并发现其与周围环境的极性有关。用涉及整个平面分子的瞬态的内酰胺-内酰胺样互变异构现象来解释这种现象。量子化学计算通过解释光谱结构来支持实验结果，并可以将内酰胺类化合物制成1,4-或3,4-本地化形式。

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