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Lead nitrate is an inorganic salt, commonly used for the accurate temperature determination in the solid state NMR spectroscopy, due to the strong temperature dependence of the 207Pb chemical shift. As the reason for this phenomenon remained unknown, the main purpose of this study was to explain this temperature dependence at the molecular level. To achieve this, combined CASTEP geometry optimization, quantum molecular dynamics at chosen temperatures and GIPAW NMR computations were performed. Due to the previous literature reports on inaccuracy in the calculation of 207Pb NMR parameters using GIPAW, a large emphasis was put on the optimization of computational method. The application of quantum molecular dynamics provided the simulation of the temperature‐dependent vibrational motions and enabled to accurately compute the changes in the value of Pb δiso resulting from them. © 2018 Wiley Periodicals, Inc. This study aims to explain, at the molecular level, the experimentally observed temperature dependence of 207Pb isotropic chemical shift value in the solid state NMR spectra of lead nitrate. For this purpose combined CASTEP geometry optimization, quantum molecular dynamics at chosen temperatures and GIPAW calculations of NMR parameters were performed. The influence of temperature‐depending vibrational motions on the NMR parameters was precisely reflected in the calculations results. [ABSTRACT FROM AUTHOR]

Abstract: In this paper the comparative structural analysis of a series of compounds (methyl α-d-glucopyranoside, methyl 4,6-O-ethylidene-α-d-glucopyranoside (2), methyl 2,3-di-O-nitro-4,6-O-ethylidene-α-d-glucopyranoside and methyl 3-O-nitro-4,6-O-ethylidene-α-d-glucopyranoside) by way of synthesis leading to methyl 3-O-nitro-α-d-glucopyranoside (5) is reported. The title compound (5) is a novel d-glucosidic mononitrate having potential biological activity against cardiovascular diseases. The structural analysis was supported by single-crystal X-ray diffraction (XRD), 13C CP/MAS NMR spectroscopy and DFT calculations. In the case of 2 and 5, XRD analysis could not be performed due to the fact that 2 is highly hygroscopic and 5 forms improper crystals. However, the molecular structures of 2 and 5 were obtained on the basis of experimental (existing XRD data for similar compounds) and theoretical (DFT optimization) approaches. This showed of very good agreement with the 13C CP/MAS NMR spectral data. [Copyright &y& Elsevier]

Abstract: Comprehensive structural analyses of methyl 2,4,6-tri-O-acetyl-3-O-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)-β-d-galactopyranoside (1) and methyl 3,4,6-tri-O-acetyl-2-O-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)-β-d-galactopyranoside (2) have been performed. The analyses combined experimental and theoretical methods: single-crystal and powder X-ray diffraction and 13C CP/MAS NMR spectroscopy served as experimental techniques, whereas the grid search of the conformers of disaccharides implemented by genetic algorithm was chosen as the theoretical method. One of the calculated conformers of 1 fits the experimental structure very well. Although the two best conformations of 2 are of similar energy, their structures are significantly different. Probably therefore 2 cannot form any crystallographic forms and is amorphous. [Copyright &y& Elsevier]