Department of Physics, University of Warwick, Coventry, UK.
Pharmaceutical Development, AstraZeneca, Macclesfield, UK.
Magn Reson Chem. 2020 Nov;58(11):1026-1035. doi: 10.1002/mrc.5021. Epub 2020 Mar 29.
Single-crystal X-ray diffraction structures of the 5-amino-2-methylpyridinium hydrogen fumarate salt have been solved at 150 and 300 K (CCDC 1952142 and 1952143). A base-acid-base-acid ring is formed through pyridinium-carboxylate and amine-carboxylate hydrogen bonds that hold together chains formed from hydrogen-bonded hydrogen fumarate ions. H and C chemical shifts as well as N shifts that additionally depend on the quadrupolar interaction are determined by experimental magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) and gauge-including projector-augmented wave (GIPAW) calculation. Two-dimensional homonuclear H- H double-quantum (DQ) MAS and heteronuclear H- C and N- H spectra are presented. Only small differences of up to 0.1 and 0.6 ppm for H and C are observed between GIPAW calculations starting with the two structures solved at 150 and 300 K (after geometry optimisation of atomic positions, but not unit cell parameters). A comparison of GIPAW-calculated H chemical shifts for isolated molecules and the full crystal structures is indicative of hydrogen bonding strength.
5-氨基-2-甲基吡啶富马酸盐的单晶 X 射线衍射结构分别在 150 和 300 K 下解出（CCDC 1952142 和 1952143）。通过质子化的吡啶盐和胺盐与富马酸的羧酸盐之间的氢键形成了一个碱基-酸-碱基-酸环，这些氢键将由氢键连接的富马酸离子组成的链固定在一起。通过实验魔角旋转（MAS）固态核磁共振（NMR）和包含度量的赝势增强波（GIPAW）计算确定了 H 和 C 化学位移以及除了取决于四极相互作用之外的 N 位移。给出了二维同核 H-H 双量子（DQ）MAS 和异核 H-C 和 N-H 谱。对于从在 150 和 300 K 下解出的两个结构开始的 GIPAW 计算，仅观察到 H 和 C 的化学位移差异最大为 0.1 和 0.6 ppm（在原子位置的几何优化后，但不包括晶胞参数）。对于孤立分子和完整晶体结构的 GIPAW 计算的 H 化学位移的比较表明了氢键的强度。
