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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Formation and Decay Behaviors of Laser-Induced Transient Species from Pyrene Derivatives 1. Spectral Discrimination and Decay Mechanisms in Aqueous Solution
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Formation and Decay Behaviors of Laser-Induced Transient Species from Pyrene Derivatives 1. Spectral Discrimination and Decay Mechanisms in Aqueous Solution

机译：Laser衍生物激光诱导的瞬态物种的形成和衰变行为1.水溶液中的光谱鉴别和衰变机理

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The ultraviolet and visible absorption spectra of laser-induced transient species from the following pyrene derivatives were measured in aqueous or aqueous ethanol solution: sodium pyrenesulfonate (NaPS), tetrasodium pyrenetetrasulfonate (Na_4PS_4), pyrenecarboxylic acid (HPC), and pyrenebutyric acid (HPB). The major transient species contributing to the intense absorption peaks were revealed on the basis of the quenching experiments. The absorption spectra of triplets, as well as cation radicals, were separable from the other transients by selecting the experimental conditions (atmosphere, coexisting quencher, and delay time). The cation radicals produced from PS~-, PB~- and PC~- anions showed an absorption maximum at ～460 nm, close to that of pyrene cation radical. Their decay behaviors in the absence of any additional quenchers were dominated by bimolecular reaction kinetics with each parent molecule, of which the rate constants were very similar. This result is consistent with the previous proposal that these cation radicals exist as zwitterions such as P~(·+)S~-. The cation radical from Na_4PS_4 showed a strong absorption peak at 505 nm and exhibited different decay behaviors, suggesting that this cation radical appears not to be a simple zwitterion. Three specific quenchers, I~-, OH~-, and SO_3~(2-), were found to strongly accelerate the decay rates of these cation radicals. CH_3SO_3~- anion, mimicking the headgroup of tentative anionic surfactants, and several inorganic anions such as ClO_4~- were poor quenchers for the cation radicals even at the highest concentration. We also discussed the origin of two additional peaks at 375 and 395 nm observed in the transient absorption spectra of NaPS and HPB. On the triplet-triplet absorption, the molar extinction coefficients of Na_4PS_4 and NaPS could be determined using the ground-state depletion method. These results are discussed in terms of applications to probe the micellar microenvironment.
机译：在乙醇水溶液或aqueous水溶液中测量了以下pyr衍生物在激光诱导的瞬态物质中的紫外和可见吸收光谱：pyr磺酸钠（NaPS），pyr四磺酸四钠（Na_4PS_4），pyr羧酸（HPC）和pyr丁酸（HPB） 。在猝灭实验的基础上揭示了导致强烈吸收峰的主要瞬态物质。通过选择实验条件（大气，共存淬灭剂和延迟时间），三重态以及阳离子自由基的吸收光谱可与其他瞬态分离。 PS〜-，PB〜-和PC_-产生的阳离子在〜460 nm处有最大吸收，与pyr阳离子接近。在没有任何其他淬灭剂的情况下，它们的衰变行为主要由与每个母体分子的双分子反应动力学决定，其速率常数非常相似。该结果与先前的建议一致，即这些阳离子自由基以两性离子形式存在，例如P〜（·+）S〜-。来自Na_4PS_4的阳离子自由基在505 nm处显示出很强的吸收峰，并表现出不同的衰减行为，这表明该阳离子自由基似乎不是简单的两性离子。发现三种特定的淬灭剂I〜-，OH〜-和SO_3〜（2-）可以强烈加速这些阳离子自由基的衰减速率。模仿暂定阴离子表面活性剂头基的CH_3SO_3〜-阴离子和几种无机阴离子（如ClO_4〜-）即使在最高浓度下也不能作为阳离子自由基的猝灭剂。我们还讨论了在NaPS和HPB的瞬态吸收光谱中观察到的375和395 nm处两个附加峰的起源。关于三重态三重态吸收，可以使用基态耗竭法确定Na_4PS_4和NaPS的摩尔消光系数。根据探测胶束微环境的应用讨论了这些结果。

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