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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Aromatic Stabilization and Hybridization Trends in Photoelectron Imaging of Heterocyclic Radicals and Anions
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Aromatic Stabilization and Hybridization Trends in Photoelectron Imaging of Heterocyclic Radicals and Anions

机译：杂环自由基和阴离子的光电子成像中的芳香族稳定和杂化趋势

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We examine the photoelectron spectra and laboratory-frame angular distributions in the photodetachment of furanide (C4H3O-), thiophenide (C4H3S-), and thiazolide (C3H2NS-) and compare the results to the previously reported studies of pyridinide (C5H4N-) and oxazolide (C3H2NO-). Using the mixed s-p model for the angular distributions, the results are interpreted in terms of the effective fractional p character of the highest-occupied molecular orbitals of these heterocyclic anions, revealing trends related to the aromaticity. We conclude that aromatic stabilization across a series of systems may be tracked using the photoelectron angular distributions. In addition, we report an improved (higher-precision) electron affinity (EA) for the thiophenyl radical, EA(center dot C4H3S) = 2.089(8) eV. The EA of thiazolyl falls within the 2.5(1) eV range, but it is not clear if this determination corresponds to the 2- or 5-cyclic species or the 2-ring-open isomer. These results are analyzed in conjunction with the properties of other heterocyclic radicals (pyridinyl, furanyl, and oxazolyl) and interpreted in terms of the C-H bond dissociation energies (BDEs) of the corresponding closed-shell molecules. The BDEs of all five-membered-ring heterocyclics studied fall within the 116-120 kcal/mol range, contrasting the lower BDE = 110.4(2.0) kcal/mol of the more aromatic six-membered-ring pyridine. The observed aromaticity trends are consistent with the findings derived from the anion photoelectron angular distributions.
机译：我们研究了呋喃化物（C4H3O-），噻吩（C4H3S-）和噻唑化物（C3H2NS-）的光解中的光电子能谱和实验室框架角分布，并将结果与​​以前报道的吡啶化物（C5H4N-）和恶唑化物的研究进行了比较。 （C3H2NO-）。使用混合s-p模型的角度分布，可以根据这些杂环阴离子的最高占据分子轨道的有效分数p特性来解释结果，从而揭示与芳香性有关的趋势。我们得出的结论是，可以使用光电子角分布来跟踪整个系统中的芳香族稳定化作用。此外，我们报告了对硫代苯基的改进的（更高精确度）电子亲和力（EA），EA（中心点C4H3S）= 2.089（8）eV。噻唑基的EA处于2.5（1）eV范围内，但尚不清楚该测定是对应于2-或5-环种类还是2-开环异构体。将这些结果与其他杂环基团（吡啶基，呋喃基和恶唑基）的性质一起进行分析，并根据相应闭壳分子的C-H键解离能（BDE）进行解释。研究的所有五元环杂环的BDE都在116-120 kcal / mol的范围内，相比之下，较芳香的六元环吡啶的BDE = 110.4（2.0）kcal / mol较低。观察到的芳族趋势与从阴离子光电子角分布得到的发现是一致的。

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