Polymorphism of N,N'-diacetylbiuret studied by solid-state 13C and 15N NMR spectroscopy, DFT calculations, and X-ray diffraction.
Polymorphism of N,N'-diacetylbiuret studied by solid-state 13C and 15N NMR spectroscopy, DFT calculations, and X-ray diffraction.
复制标题
通过固态 13C 和 15N NMR 光谱、DFT 计算和 X 射线衍射研究 N,N-二乙酰基缩二脲的多晶型。
作者：
S. Macholl;D. Lentz;F. Börner;G. Buntkowsky
本文采用固体和液体核磁共振谱、X射线衍射和密度泛函理论计算相结合的方法，研究了N，N '-二乙酰缩二脲（DAB）固体多晶的分子构型和晶体结构。最初进行纯NMR研究（“NMR晶体学”），因为可用的DAB单晶不适合X射线衍射。固态13 C NMR光谱揭示了从不同化学程序获得的两种多晶型修饰（α-和β-DAB）的意外存在。几种NMR技术被应用于一个彻底的表征的分子系统，揭示化学位移各向异性（CSA）张量的选定的核在固态，在液态的化学位移，和在固态的分子动力学。DAB在溶液中的动态NMR光谱揭示了两种不同构型之间的交换，这提出了一个问题，即在溶液中发现的两种不同构型与在固态中发现的两种多晶型修饰之间是否存在相关性？通过使用这些知识，设计了一种新的结晶协议，导致适合X射线衍射的单晶生长。X-射线衍射数据表明，两种多晶型中存在相同的对称构型，但晶体中的堆积模式不同。在这两种情况下，氢键导致DAB分子平面的形成。额外的对称元素，在α-DAB的情况下的双重螺旋和在β-DAB的情况下的c-滑移平面，导致每个分子的更对称（α-DAB）或不对称（β-DAB）的分子间氢键模式。
The molecular configuration and crystal structure of solid polycrystalline N,N'-diacetylbiuret (DAB), a potential nitrogen-rich fertilizer, have been analyzed by a combination of solid- and liquid-state NMR spectroscopy, X-ray diffraction, and DFT calculations. Initially a pure NMR study ("NMR crystallography") was performed as available single crystals of DAB were not suitable for X-ray diffraction. Solid-state 13C NMR spectra revealed the unexpected existence of two polymorphic modifications (alpha- and beta-DAB) obtained from different chemical procedures. Several NMR techniques were applied for a thorough characterization of the molecular system, revealing chemical shift anisotropy (CSA) tensors of selected nuclei in the solid state, chemical shifts in the liquid state, and molecular dynamics in the solid state. Dynamic NMR spectroscopy of DAB in solution revealed exchange between two different configurations, which raised the question, is there a correlation between the two different configurations found in solution and the two polymorphic modifications found in the solid state? By using this knowledge, a new crystallization protocol was devised which led to the growth of single crystals suitable for X-ray diffraction. The X-ray data showed that the same symmetric configuration is present in both polymorphic modifications, but the packing patterns in the crystals are different. In both cases hydrogen bonds lead to the formation of planes of DAB molecules. Additional symmetry elements, a two-fold screw in the case of alpha-DAB and a c-glide plane in the case of beta-DAB, lead to a more symmetric (alpha-DAB) or asymmetric (beta-DAB) intermolecular hydrogen-bonding pattern for each molecule.
通过 (13)C 固态核磁共振波谱研究 3,6-二氯-2,5-二羟基对苯二甲酸二甲酯的多晶型物。
影响因子：
15
作者：
Strohmeier,M;Orendt,AM;Alderman,DW;Grant,DM
通讯作者：
Grant,DM