Abma Grite L, Parkes Michael A, Horke Daniel A
Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
Department of Chemistry, University College London, 20 Gordon Street, WC1H 0AJ London, United Kingdom.
J Phys Chem Lett. 2024 May 2;15(17):4587-4592. doi: 10.1021/acs.jpclett.4c00768. Epub 2024 Apr 24.
Tautomers are ubiquitous throughout chemistry and typically considered inseparable in solution. Yet (bio)chemical activity is highly tautomer-specific, with common examples being the amino and nucleic acids. While tautomers exist in an equilibrium in solution, in the cold environment of a molecular beam the barrier to tautomerization is typically much too high for interconversion, and tautomers can be considered separate species. Here we demonstrate the first separation of tautomers within a molecular beam and the production of tautomerically pure gas-phase samples. We show this for the 2-pyridone/2-hydroxypyridine system, an important structural motif in both uracil and cytosine. Spatial separation of the tautomers is achieved via electrostatic deflection in strong inhomogeneous fields. We furthermore collect tautomer-resolved photoelectron spectra using femtosecond multiphoton ionization. This paves the way for studying the structure-function-dynamic relationship on the level of individual tautomers, using approaches that typically lack the resolution to do so, such as ultrafast dynamics experiments.
互变异构体在整个化学领域中普遍存在，通常在溶液中被认为是不可分离的。然而，（生物）化学活性具有高度的互变异构体特异性，常见的例子是氨基酸和核酸。虽然互变异构体在溶液中处于平衡状态，但在分子束的低温环境中，互变异构化的势垒通常过高，无法进行相互转化，互变异构体可被视为不同的物种。在此，我们展示了分子束中互变异构体的首次分离以及互变异构纯气相样品的制备。我们以2-吡啶酮/2-羟基吡啶体系为例进行了展示，该体系在尿嘧啶和胞嘧啶中都是重要的结构基序。互变异构体的空间分离是通过强非均匀场中的静电偏转实现的。此外，我们使用飞秒多光子电离收集了互变异构体分辨的光电子能谱。这为利用通常缺乏分辨率的方法（如超快动力学实验）研究单个互变异构体水平上的结构-功能-动力学关系铺平了道路。
