Proton Transfer, Hydrogen Bonding, and Disorder: Nitrogen Near-Edge X-ray Absorption Fine Structure and X-ray Photoelectron Spectroscopy of Bipyridine-Acid Salts and Co-crystals
Proton Transfer, Hydrogen Bonding, and Disorder: Nitrogen Near-Edge X-ray Absorption Fine Structure and X-ray Photoelectron Spectroscopy of Bipyridine-Acid Salts and Co-crystals
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DOI：
10.1021/cg5018278
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发表时间：
2015-04-01
影响因子：
3.8
通讯作者：
Schroeder, Sven L. M.
中科院分区：
文献类型：
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作者：
Stevens, Joanna S.;Newton, Lauren K.;Schroeder, Sven L. M.
通过一系列多组分的联吡啶酸体系和X射线光电子能谱(XPS)数据，研究了近边X射线吸收精细结构(NEXAFS)光谱对Bronsted施主和固态氮的质子化状态的敏感性。氮的K边NEXAFS中的1s-gt；1pi*共振发生了大的向高能的转变，质子从酸转移到联吡啶碱分子，并允许指定为盐(C-NH+)，峰比提供了存在的氮物种类型的化学计量比。在氮的XPS中观察到相应的C-NH+的结合能移动，清楚地识别了质子化和盐的形成。用这两种技术观察到的相对于共晶(C-N)的未质子化氮的类似的幅度变化表明，化学态(初始态)效应占主导地位。这两种技术的结果都揭示了识别质子转移、氢键无序的敏感性，甚至有可能区分氢键长度与氮的变化。
The sensitivity of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to Bronsted donation and the protonation state of nitrogen in the solid state is investigated through a series of multicomponent bipyridine-acid systems alongside X-ray photoelectron spectroscopy (XPS) data. A large shift to high energy occurs for the 1s -> 1 pi* resonance in the nitrogen K-edge NEXAFS with proton transfer from the acid to the bipyridine base molecule and allows assignment as a salt (C-NH+), with the peak ratio providing the stoichiometry of the types of nitrogen species present. A corresponding binding energy shift for C-NH+ is observed in the nitrogen XPS, clearly identifying protonation and formation of a salt. The similar magnitude shifts observed with both techniques relative to the unprotonated nitrogen of co-crystals (C-N) suggest that the chemical state (initial-state) effects dominate. Results from both techniques reveal the sensitivity to identify proton transfer, hydrogen bond disorder, and even the potential to distinguish variations in hydrogen bond length to nitrogen.