Department of Chemistry, Redeemer University, Ancaster, ON, L9K 1J4, Canada.
Department of Chemistry, Redeemer University, Ancaster, ON, L9K 1J4, Canada.
Solid State Nucl Magn Reson. 2023 Feb;123:101848. doi: 10.1016/j.ssnmr.2022.101848. Epub 2022 Dec 23.
Hydrogen bonding plays an important role in the structure and function of a wide range of materials. Solid-state H nuclear magnetic resonance (NMR) spectroscopy provides a very sensitive tool to investigate the local structure of hydrogen atoms involved in hydrogen bonding. While there is extensive H solid-state NMR data on O-H - - O hydrogen bonding in solid carboxylic acids, there has been no systematic H solid-state NMR studies of hydroxyl groups in carbohydrates (and hydroxyl groups in general). With a view to studying the hydrogen bonding in more complex materials such as cellulose polymorphs, we carried out a detailed solid-state H NMR investigation of the model compounds α-d-glucose and α-d-glucose monohydrate. Through a combination of fast magic-angle spinning (MAS), combined rotation and multiple pulse spectroscopy (CRAMPS), and two-dimensional (2D) correlation experiments carried out at ultrahigh magnetic fields, it was possible to assign all of the aliphatic (CH), hydroxyl (OH), and water (HO) H chemical shifts in both forms of α-d-glucose. Plane-wave DFT calculations were employed to improve the hydrogen atom positions for α-d-glucose monohydrate and to calculate H chemical shifts, providing additional support for the experimentally determined peak assignments. Finally, the relationship between the hydroxyl H chemical shifts and their hydrogen bonding geometry was investigated and compared to the well-established relationship for carboxylic acid protons.
氢键在广泛的材料的结构和功能中起着重要作用。固态 H 核磁共振（NMR）光谱学提供了一种非常灵敏的工具来研究涉及氢键的氢原子的局部结构。虽然有关于固态羧酸中 O-H - - O 氢键的大量 H 固态 NMR 数据，但对于碳水化合物（和一般的羟基）中的羟基，没有系统的 H 固态 NMR 研究。为了研究更复杂的材料（如纤维素多晶型物）中的氢键，我们对模型化合物α-d-葡萄糖和α-d-葡萄糖一水合物进行了详细的固态 H NMR 研究。通过快速魔角旋转（MAS）、联合旋转和多脉冲光谱（CRAMPS）以及在超高磁场下进行的二维（2D）相关实验的组合，有可能对两种形式的α-d-葡萄糖中的所有脂肪族（CH）、羟基（OH）和水（HO）H 化学位移进行分配。平面波 DFT 计算被用来改进α-d-葡萄糖一水合物的氢原子位置并计算 H 化学位移，为实验确定的峰分配提供了额外的支持。最后，研究了羟基 H 化学位移与其氢键几何形状之间的关系，并与羧酸质子的既定关系进行了比较。
