Grześkiewicz Anita M, Kubicki Maciej
Faculty of Chemistry, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 8, 61-614 Poznan, Poland.
Materials (Basel). 2021 Dec 28;15(1):223. doi: 10.3390/ma15010223.
High-quality crystals of a certain polymorphic form of thiobarbituric acid containing both keto and enol tautomers in the asymmetric unit were obtained. High-resolution X-ray diffraction data up to sinθ/λ = 1.0 Å were collected and subsequently successfully used for the refining of the multipolar model of electron density distribution. The use of a crystal containing both ketone and enol forms allowed a direct comparison of the topological analysis results and a closer look at the differences between these two forms. The similarities and differences between the deformation densities, electrostatic potentials, Laplacian maps and bond characteristics of the tautomers were analysed. Additionally, the spectrum of the intermolecular interactions was identified and studied from classical, relatively strong N-H···O and O-H···O hydrogen bonds through weaker N-H···S hydrogen bonds to weak interactions (for instance, C-H···O, C-H···S and N···O). The results of these studies point toward the importance of including both the geometrical features and the details of the electron density distribution in the analysis of such weak interactions.
获得了一种特定多晶型硫代巴比妥酸的高质量晶体，其不对称单元中同时包含酮式和烯醇式互变异构体。收集了高达sinθ/λ = 1.0 Å的高分辨率X射线衍射数据，并随后成功用于电子密度分布多极模型的精修。使用同时包含酮式和烯醇式的晶体使得能够直接比较拓扑分析结果，并更深入地了解这两种形式之间的差异。分析了互变异构体的变形密度、静电势、拉普拉斯图和键特征之间的异同。此外，还识别并研究了分子间相互作用谱，从经典的、相对较强的N-H···O和O-H···O氢键到较弱的N-H···S氢键，再到弱相互作用（例如，C-H···O、C-H···S和N···O）。这些研究结果表明，在分析此类弱相互作用时，同时考虑几何特征和电子密度分布细节非常重要。
