首页|晶体学辅助的2-吡啶甲酸固体13C化学位移理论计算归属(英文)

晶体学辅助的2-吡啶甲酸固体13C化学位移理论计算归属(英文)

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  • 国家科技期刊平台
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有机分子的互变异构现象在溶液中较为常见.而对于有机固体而言,存在互变异构可能的分子常以单一的能量最稳定的异构体形式存在.2-吡啶甲酸(PCA)是一个较为罕见的案例,它的晶体结构中同时存在有中性分子和两性离子两种互变异构体.由于超长的质子纵向弛豫时间,PCA的固体13C核磁共振(NMR)实验的化学位移归属存在困难.密度泛函理论(DFT)计算,特别是基于周期性模型的方式是一种可以准确快捷归属其化学位移的方案.然而,由于PCA结构中活泼质子的占位无序,其结构并不能直接或经简单处理后递交计算.本文中,我们通过晶体学手段构建了一个虚拟晶体结构.基于该虚拟结构的13C化学位移计算值可与实验值准确吻合.此外,不同互变异构状态的PCA表现出不同的特征化学位移,这一信息可被用来分析PCA在其晶体复合物中的分子状态.
13C Chemical Shift Assignment of Solid 2-Picolinic Acid by DFT/Crystallography Integrated Approach
The tautomerism of organic molecules is widely observed in solution. While for solid organic chemicals, molecules often exist in the most stable tautomeric form. 2-Picolinic acid (PCA) is a very rare case which contains both the neutral molecules and zwitterions in the same crystal structure. Chemical shift assignment for PCA by experimental approach, e.g., 2D NMR methods, is extremely time consuming because the 1H spin-lattice relaxation time (T1) is too long. Density functional theory (DFT) calculation, especially using a periodic model, is an alternative protocol to fix this issue. However, the original crystal structure of PCA cannot be submitted directly for the calculation task due to the proton positional disorder. In this contribution, a virtual structure was constructed via crystallography approach. Theoretical 13C chemical shifts were obtained basing on this virtual model, which are consistent with the experimental values. Also, both neutral PCA and zwitterion demonstrated their featured chemical shifts, such information can be utilized to analyze the molecular states of PCA in its crystalline complexes.

molecular tautomerismsolid-state NMRDFT calculationzwitterionsingle crystal X-ray diffraction

张之杰、李端秀、罗春、仇汝臣、邓宗武、张海禄

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青岛科技大学化工学院,山东青岛 266042

磁共振波谱与影像实验室,中国科学院苏州纳米技术与纳米仿生研究所,江苏苏州 215123

分子互变异构 固体核磁共振 DFT计算 两性离子 单晶X射线衍射

National Natural Science Foundation of ChinaYouth Innovation Promotion Association of CAS

216732792012242

2020

波谱学杂志
中国科学院武汉物理与数学研究所 中国物理学会波谱学专业委员会

波谱学杂志

CSTPCD北大核心
影响因子：0.569
ISSN：1000-4556
年,卷(期)：2020.37(1)
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