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Probing the structure and dynamics of the heterocyclic PAH xanthene and its water complexes with infrared and microwave spectroscopy
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2024-08-30 , DOI: 10.1039/d4cp03030c
Donatella Loru 1 , Wenhao Sun 1 , Hugo Nootebos 2 , Amanda L Steber 3 , Piero Ferrari 2 , Melanie Schnell 1, 4
Affiliation  

To assess the presence of oxygen-containing polycyclic aromatic hydrocarbons (OPAHs) in the interstellar medium and understand how water aggregates on an OPAH surface, we present a comprehensive gas-phase spectroscopy investigation of the OPAH xanthene (C13H10O) and its complexes with water using IR-UV ion dip spectroscopy and chirped-pulse Fourier transform microwave spectroscopy. The infrared spectrum of xanthene shows weak features at 3.42, 3.43, and 3.47 μm, which have been suggested to partly originate from vibrational modes of PAHs containing sp3 hybridized carbon atoms, in agreement with the molecular structure of xanthene. The high resolution of rotational spectroscopy reveals a tunneling splitting of the rotational transitions, which can be explained with an out-of-plane bending motion of the two lateral benzene rings of xanthene. The nature of the tunnelling motion is elucidated by observing a similar splitting pattern in the rotational transitions of the singly-substituted 13C isotopologues. The rotational spectroscopy investigation is extended to hydrates of xanthene with up to four water molecules. Different xanthene–water binding motifs are observed based on the degree of hydration, with O–H⋯π interactions becoming preferred over O–H⋯Oxanthene interactions as the degree of hydration increases. A structural comparison with water complexes of related molecular systems highlights the impact of the substrate's shape and chemical composition on the arrangement of the surrounding water molecules.

中文翻译:


用红外和微波光谱研究杂环 PAH 氧杂蒽及其水络合物的结构和动力学



为了评估星际介质中含氧多环芳烃 (OPAH) 的存在并了解水如何在 OPAH 表面聚集,我们使用 IR-UV 离子浸入光谱和啁啾脉冲傅里叶变换微波光谱对 OPAH 黄元 (C13H10O) 及其与水的络合物进行了全面的气相光谱研究。氧杂黄酮的红外光谱在 3.42、3.43 和 3.47 μm 处显示出弱特征,这被认为部分来源于含有 sp3 杂化碳原子的 PAH 的振动模式,这与氧杂黄酮的分子结构一致。旋转光谱的高分辨率揭示了旋转转变的隧穿分裂,这可以用氧杂蒽的两个横向苯环的平面外弯曲运动来解释。通过在单取代的 13C 同位素的旋转跃迁中观察类似的分裂模式来阐明隧道运动的性质。旋转光谱研究扩展到具有多达四个水分子的氧杂蒽水合物。根据水合程度观察到不同的氧杂黄凰-水结合基序,随着水合程度的增加,O-H⋯π 相互作用成为优于 O-H⋯O氧杂蒽相互作用的优选因素。与相关分子系统的水复合物的结构比较突出了底物的形状和化学成分对周围水分子排列的影响。
更新日期:2024-09-04
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