Imidazole-2-carboxaldehyde (IC) can be generated in atmospheric waters and absorbs solar radiation in the near UV region to produce its excited triplet state (³IC), which contributes to the formation of a secondary organic aerosol (SOA). The photoreactivity of IC is significantly influenced by its surroundings, such as water and acidic environment, because IC is capable of transforming into gem-diol under above conditions. Meanwhile, the electron configuration of ³IC is critical in elucidating the reaction mechanism of ³IC with other anthropogenic and biogenic volatile organic compounds (VOCs). In this study, steady-state and time-resolved resonance Raman as well as transient absorption spectroscopic experiments were conducted to provide vibrational and kinetic information on IC and ³IC in the presence of water and acid conditions. Using density functional theory (DFT) calculations, the H-bonding at the carbonyl O was confirmed and the hydrated structure of IC and ³IC was determined. 1,4-Cyclohexadiene is a good hydrogen donor, and it has a second-order rate constant of ∼10⁷ M^–1 s^–1 toward ³IC. The results of CASSCF calculations suggest that the hydrogen abstraction may involve the transition from the ππ* to nπ* triplet state via the surface-crossing point.

中文翻译：

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咪唑-2-甲醛及其激发三重态的结构和电子构型：共振拉曼、瞬态吸收光谱和DFT计算研究

咪唑-2-甲醛（IC）可以在大气水中产生，并吸收近紫外区域的太阳辐射产生其激发三重态（³ IC），这有助于形成二次有机气溶胶（SOA）。IC的光反应性受周围环境如水和酸性环境的显着影响，因为IC在上述条件下能够转化为宝石二醇。^{同时， 3} IC的电子构型对于阐明³ IC 与其他人为和生物挥发性有机化合物（VOC）的反应机制至关重要。在这项研究中，进行了稳态和时间分辨共振拉曼以及瞬态吸收光谱实验，以提供 IC 和³ IC 在水和酸条件下的振动和动力学信息。利用密度泛函理论（DFT）计算，证实了羰基O处的H键，并确定了IC和^{3 IC的水合结构。}1,4-环己二烯是一种良好的氢供体，其二阶速率常数对于³ IC而言为∼10 ⁷ M ^–1 s ^–1。CASSCF计算结果表明，夺氢可能涉及通过表面交叉点从ππ*到nπ*三重态的转变。