The characterization of the three-dimensional structure of solids is of major importance, especially in the pharmaceutical field. In the present work, NMR crystallography methods are applied with the aim to refine the crystal structure of carbimazole, an active pharmaceutical ingredient used for the treatment of hyperthyroidism and Grave’s disease. Starting from previously reported X-ray diffraction data, two refined structures were obtained by geometry optimization methods. Experimental 1H and 13C isotropic chemical shift measured by the suitable 1H and 13C high-resolution solid state NMR techniques were compared with DFT-GIPAW calculated values, allowing the quality of the obtained structure to be experimentally checked. The refined structure was further validated through the analysis of 1H-1H and 1H-13C 2D NMR correlation experiments. The final structure differs from that previously obtained from X-ray diffraction data mostly for the position of hydrogen atoms.

Cesium lead bromide perovskite (CsPbBr3) nanocrystals have raised impressive interest as efficient and stable optoelectronic materials. Size and morphology play important roles in the final performances of these materials and advanced characterization studies are needed to elucidate structural and surface properties. In this work, CsPbBr3 cubic nanocrystals were obtained by colloidal synthesis and characterized by multinuclear Solid State NMR (SSNMR), complemented by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and optical spectroscopy. The multinuclear NMR approach allowed the different components of the nanocubes to be separately observed. In particular, the surface ligands and their interactions with the nanocubes surface were investigated by 1H and 13C NMR experiments, while the structural investigation of the perovskite nanocubes was addressed by exploiting 207Pb and 133Cs spectral properties in comparison with bulk CsPbBr3. Static 207Pb NMR spectra indicated a possible contribution of chemical shift anisotropy from the 207Pb nuclei of the outer layer. The 133Cs NMR spectra showed signals with different chemical shifts for cesium atoms in at least three regions of the nanocubes, from the inner core to the surface, which were interpreted in terms of cubic layers with different distances from the surface using a simple geometrical model. This interpretation was also supported by 133Cs longitudinal relaxation time measurements.

Dynamic properties of carbimazole (a drug used in hyperthyroidism treatment) were thoroughly investigated by combining solid-state nuclear magnetic resonance spectroscopy and quasielastic neutron scattering with periodic density functional theory (plane-wave DFT) and molecular dynamics simulations. These complementary methods allowed the full description of internal carbimazole motions. Particularly, in crystalline carbimazole, only the reorientations of the two methyl groups were found to be active in the explored timescale. The combination of different techniques allowed the quantitative characterization of the two methyl reorientations, which differ by almost 2 orders of magnitude in the timescale, in agreement with results previously reported in the literature for methyl groups in similar chemical environments. These results could also assume a particular relevance considering the role of methyl groups in determining the biochemical and biological activities of active pharmaceutical ingredients.