Abstract
We report a strategy for structure determination of organic materials in which complete solid-state nuclear magnetic resonance (NMR) spectral data is utilized within the context of structure determination from powder X-ray diffraction (XRD) data. Following determination of the crystal structure from powder XRD data, first-principles density functional theory-based techniques within the GIPAW approach are exploited to calculate the solid-state NMR data for the structure, followed by careful scrutiny of the agreement with experimental solid-state NMR data. The successful application of this approach is demonstrated by structure determination of the 1:1 cocrystal of indomethacin and nicotinamide. The 1H and 13C chemical shifts calculated for the crystal structure determined from the powder XRD data are in excellent agreement with those measured experimentally, notably including the two-dimensional correlation of 1H and 13C chemical shifts for directly bonded 13C–1H moieties. The key feature of this combined approach is that the quality of the structure determined is assessed both against experimental powder XRD data and against experimental solid-state NMR data, thus providing a very robust validation of the veracity of the structure.
Highlights
In order to understand and rationalize the physicochemical properties of crystalline solids, an essential prerequisite is to establish the structural properties of the material of interest
The crystal structure of IND−NIC was determined in the present work directly from powder X-ray diffraction (XRD) data, employing the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement
We emphasize that the approach developed in the present article for using complete solid-state nuclear magnetic resonance (NMR) spectral data within the context of structure determination from powder XRD data allows the quality of the crystal structure determined from the powder XRD data to be assessed and validated both against the experimental powder XRD data and against the experimental solid-state NMR data
Summary
In order to understand and rationalize the physicochemical properties of crystalline solids, an essential prerequisite is to establish the structural properties of the material of interest. The development of new and improved strategies for determining the structural properties of crystalline materials has the potential to make significant impact across the broad range of fields within the physical sciences in which knowledge of crystal structure is required. To establish the structural properties of such materials, the most direct approach is to use powder XRD, it is important to emphasize that carrying out structure determination from powder XRD data is significantly more challenging than from single-crystal XRD data. The opportunities in this regard have improved significantly in recent years as a consequence of progress in the development of new data analysis techniques[1−9] (such as the direct-space strategy for structure solution, which has made a significant impact in the case of structure determination of organic molecular solids from powder XRD data)
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