Mauney Daniel T, Maner Jonathon A, Duncan Michael A
Department of Chemistry, University of Georgia , Athens, Georgia 30602, United States.
J Phys Chem A. 2017 Sep 21;121(37):7059-7069. doi: 10.1021/acs.jpca.7b07180. Epub 2017 Sep 8.
Protonated ions of acetylacetone, H(Hacac), and their argon-tagged analogues are produced via a pulsed discharge and cooled in a supersonic expansion. These ions are mass analyzed, selected in a time-of-flight spectrometer, and studied with infrared laser photodissociation spectroscopy using the method of rare-gas atom tagging. Computational studies at the DFT/B3LYP level are employed to elucidate the structures and spectra of these ions, which are expected to exist as either enol- or keto-based tautomers. The protonated acetylacetone ion is found to form a single enol-based isomer. Adding one or two water molecules to this ion, for example, H(Hacac)(HO), produces primarily enol-based structures, although a small concentration of keto structures also contribute to the spectra. The vibrational patterns resulting from hydrogen bonding in these systems are not well-described by theory. Addition of a third water molecule to form the H(Hacac)(HO) ion causes a significant change in the spectroscopy, attributed to proton transfer from the H(Hacac) ion into the water solvent.
乙酰丙酮的质子化离子H(Hacac)及其氩标记类似物通过脉冲放电产生，并在超声速膨胀中冷却。这些离子进行质量分析，在飞行时间光谱仪中进行选择，并使用稀有气体原子标记法通过红外激光光解离光谱进行研究。采用DFT/B3LYP水平的计算研究来阐明这些离子的结构和光谱，预计它们以烯醇式或酮式互变异构体形式存在。发现质子化乙酰丙酮离子形成单一的烯醇式异构体。例如，向该离子添加一个或两个水分子，即H(Hacac)(HO)，主要产生烯醇式结构，尽管少量的酮式结构也对光谱有贡献。这些体系中氢键导致的振动模式理论上无法很好地描述。添加第三个水分子形成H(Hacac)(HO)离子会导致光谱发生显著变化，这归因于质子从H(Hacac)离子转移到水溶剂中。
