O2-·[Polar VOC] Complexes: H-Bonding versus Charge-Dipole Interactions, and the Noninnocence of Formaldehyde.
O2-·[Polar VOC] Complexes: H-Bonding versus Charge-Dipole Interactions, and the Noninnocence of Formaldehyde.
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DOI：
10.1021/acs.jpca.7b05124
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发表时间：
2017-07
期刊：
影响因子：
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通讯作者：
K. Patros;J. Mann;C. Jarrold
中科院分区：
文献类型：
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作者：
K. Patros;J. Mann;C. Jarrold
阴离子光电子成像被用来测量的光剥离光谱的分子复合物之间形成的O2-和一系列的大气相关的极性分子，包括物种与羰基（丙酮，甲醛）和醇（乙醇，丙烯醇，丁烯醇）。实验光谱进行了分析，使用组合的Franck-Condon模拟和电子结构计算。强的电荷-偶极相互作用和氢键使络合阴离子相对于中性离子稳定，从而产生了一个约100。1 eV的电子结合能增加相对于裸O2-，与H-键合的复合物中的效果更明显。此外，当与裸O2相比时，复合物中O2-局部πg轨道的破缺简并导致低激发态O2（a 1Δg）·[极性VOC]相对于基态O2（X 3 Δ g-）·[极性VOC]的稳定。O2-·[极性VOC]复合物的光谱表现出不太明显的激光光电子角分布（PAD）。O2-·甲醛的光谱在光谱轮廓和PAD方面都是独特的。除了计算结果的基础上，这些实验结果，复杂的阴离子不能被描述为一个独特的O2-阴离子与无辜的溶剂分子合作，分子通过电荷离域耦合更强。总的来说，这些结果强调了O2 πg轨道的对称性是如何被不同的极性伙伴打破的，这可能对大气光化学和太阳辐射吸收模型（包括碰撞诱导吸收）产生影响。
Anion photoelectron imaging was used to measure the photodetachment spectra of molecular complexes formed between O2- and a range of atmospherically relevant polar molecules, including species with a carbonyl group (acetone, formaldehyde) and alcohols (ethanol, propenol, butenol). Experimental spectra are analyzed using a combination of Franck-Condon simulations and electronic structure calculations. Strong charge-dipole interactions and H-bonding stabilize the complex anions relative to the neutrals, resulting in a ca. 1 eV increase in electron binding energy relative to bare O2-, an effect more pronounced in complexes with H-bonding. In addition, broken degeneracy of the O2-local πg orbitals in the complexes results in the stabilization of the low-lying excited O2 (a 1Δg)·[polar VOC] state relative to the ground O2 (X 3Σg-)·[polar VOC] state when compared to bare O2. The spectra of the O2-·[polar VOC] complexes exhibit less pronounced laser photoelectron angular distribution (PADs). The spectrum of O2-·formaldehyde is unique in terms of both spectral profile and PAD. On the basis of these experimental results in addition to computational results, the complex anion cannot be described as a distinct O2- anion partnered with an innocent solvent molecule; the molecules are more strongly coupled through charge delocalization. Overall, the results underscore how the symmetry of the O2 πg orbitals is broken by different polar partners, which may have implications for atmospheric photochemistry and models of solar radiation absorption that include collision-induced absorption.