School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
UK 850 MHz Solid-state NMR Facility, Department of Physics, Millburn House, University of Warwick, Coventry CV4 7AL, UK.
Solid State Nucl Magn Reson. 2017 Oct;87:67-72. doi: 10.1016/j.ssnmr.2017.02.002. Epub 2017 Feb 13.
A H anisotropic-isotropic chemical shift correlation experiment which employs symmetry-based recoupling sequences to reintroduce the chemical shift anisotropy in ν and ultrafast MAS to resolve H sites in ν is described. This experiment is used to measure H shift parameters for L-ascorbic acid, a compound with a relatively complex hydrogen-bonding network in the solid. The H CSAs of hydrogen-bonded sites with resolved isotropic shifts can be extracted directly from the recoupled lineshapes. In combination with DFT calculations, hydrogen positions in crystal structures obtained from X-ray and neutron diffraction are refined by comparison with simulations of the full two-dimensional NMR spectrum. The improved resolution afforded by the second dimension allows even unresolved hydrogen-bonded sites H to be assigned and their shift parameters to be obtained.
一种各向异性-各向同性化学位移相关实验，采用基于对称的重耦序列在 ν 中重新引入化学位移各向异性，并利用超快 MAS 来分辨 ν 中的 H 位点。该实验用于测量 L-抗坏血酸的 H 位移参数，L-抗坏血酸是一种在固体中具有相对复杂氢键网络的化合物。可以直接从重耦线谱中提取具有分辨各向同性位移的氢键位点的 H CSA。结合密度泛函理论（DFT）计算，通过与全二维 NMR 光谱的模拟比较，对 X 射线和中子衍射获得的晶体结构中的氢位置进行精修。通过二维谱的高分辨率，甚至可以对未解耦的氢键 H 位点进行归属，并获得它们的位移参数。
