Characterization of Proton Transfer in Co-Crystals by X-ray Photoelectron Spectroscopy (XPS)
Characterization of Proton Transfer in Co-Crystals by X-ray Photoelectron Spectroscopy (XPS)
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DOI：
10.1021/cg901481q
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发表时间：
2010-03-01
影响因子：
3.8
通讯作者：
Schroeder, Sven L. M.
中科院分区：
文献类型：
--
作者：
Stevens, Joanna S.;Byard, Stephen J.;Schroeder, Sven L. M.
在分子水平上的表征建立了X射线光电子能谱（XPS）作为一种有用的技术，用于确定分子晶体中的质子转移的程度，通过研究茶碱-柠檬酸共晶体以及固态核磁共振（ssNMR）和衰减全反射傅里叶变换红外光谱（ATR-FTIR）。通过将茶碱与无水或一水柠檬酸研磨形成复合物，并通过常规分析方法和新型分析方法的组合确立为1：1共晶体。在X-射线衍射粉末图中没有来自起始材料的峰表明产物是定量形成的，元素分析和XPS显示其为1：1化学计量。热重分析表明该配合物为无水物，差示扫描量热分析表明其熔融温度与原料不同。XPS中没有C=NH+ N1s峰，N-15 ssNMR和ATR-FTIR相对于无水茶碱的位移较小，表明质子转移。因此仍然形成，没有发生。分析技术的组合允许复合物被分配其1：1共晶，而不需要单晶结构。
Characterization at the molecular level establishes X-ray photoelectron spectroscopy (XPS) as a useful technique for determining the extent of proton transfer in molecular crystals by studying theophylline-citric acid co-crystals alongside solid-state nuclear magnetic resonance (ssNMR) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). A complex has been formed by milling theophylline with either anhydrous or monohydrate citric acid and established as a 1:1 co-crystal by it combination of both conventional and novel analytical methods. The absence of peaks from the starting materials in the X-ray diffraction powder pattern indicates that the product was formed quantitatively, with elemental analysis and XPS revealing it 1:1 stoichiometry. Thermogravimetric analysis demonstrated the complex was anhydrous, with differential scanning calorimetry showing it melting temperature different from that of the starting materials. The absence of a C=NH+ N1s peak in XPS and the small magnitude of N-15 ssNMR and ATR-FTIR shifts relative to anhydrous theophylline revealed that proton transfer. and hence still formation, had not occurred. The combination of analytical techniques allows the complex to be assigned its a 1:1 co-crystal without the need for a single crystal structure.