Structural basis for the transformation pathways of the sodium naproxen anhydrate–hydrate system

Bond, Andrew D.; Cornett, Claus; Larsen, Flemming H.; Qu, Haiyan; Raijada, Dhara; Rantanen, Jukka

doi:10.1107/s2052252514015450

Cited by 27 publications

(18 citation statements)

References 27 publications

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“…Already, a term, "NMR crystallography", has been created [197][198][199] to describe an approach which combines performing experimental NMR and generating spectra with a DFT-based software in order to confirm or create the crystal structure of the studied system. It has been already proven that a research constructed in this way delivers more accurate data, compared to the separate application of these two techniques [200][201][202]. In some cases it is plainly stated that the proper designation of the hydrogen positions would not be possible at all, unless the combination of DFT and ssNMR had been used [203].…”

Section: Solid State Nmrmentioning

confidence: 99%

Periodic DFT Calculations—Review of Applications in the Pharmaceutical Sciences

2020

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In the introduction to this review the complex chemistry of solid-state pharmaceutical compounds is summarized. It is also explained why the density functional theory (DFT) periodic calculations became recently so popular in studying the solid APIs (active pharmaceutical ingredients). Further, the most popular programs enabling DFT periodic calculations are presented and compared. Subsequently, on the large number of examples, the applications of such calculations in pharmaceutical sciences are discussed. The mentioned topics include, among others, validation of the experimentally obtained crystal structures and crystal structure prediction, insight into crystallization and solvation processes, development of new polymorph synthesis ways, and formulation techniques as well as application of the periodic DFT calculations in the drug analysis.

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Section: Solid State Nmrmentioning

confidence: 99%

Periodic DFT Calculations—Review of Applications in the Pharmaceutical Sciences

2020

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“…17,21 Many of the hydrates studied in the literature are channel structures 18,[22][23][24][25] which exhibit type i behaviour, with the dehydration process being completely reversible. [26][27][28][29][30][31][32] Because of the significant structural changes involved, the dehydration behaviour of pocket hydrates 4 is more complex, following type ii) and iii) behaviour, and thus has been studied to a much lesser extent. [33][34] In this context, gaining a better understanding of hydration and dehydration mechanisms in molecular solids would allow for better control during the processing of these materials.…”

Section: Introductionmentioning

confidence: 99%

Conformational Change Initiates Dehydration in Fluconazole Monohydrate

Basford

Cameron

Cruz‐Cabeza

2020

Crystal Growth & Design

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Experimental and computational techniques have been used in combination, to monitor the dehydration process of fluconazole monohydrate (MH), this unveiling the dehydration mechanism at the molecular level. Experimentally, dehydration was observed to start at around 55 °C and complete around 100 °C, with metastable Pbca, Z'=1 polymorph (AH-C) as the sole product of dehydration (as determined by in-situ hot stage PXRD). Conformational and structural changes were identified as key in the initiation and progression of the dehydration process. Thermal expansion is most significant along the c-axis, with molecular dynamic (MD) simulations and experimental observations identifying that water migrates through the MH crystal lattice within the plane perpendicular to that direction. Water was found to migrate within the (001) plane along both the a and b-axis directions. The MD simulations revealed that water was not able to migrate within the lattice at room temperature. Migration at 70°C (342K) was plausible, but only after the hydroxyl group undergoes conformational change. The conformational change, around the hydroxyl group, is key to both the weakening of the fluconazole-water hydrogen bonding, found in the MH structure, and the promotion of the fluconazole-fluconazole hydrogen bonding, required for the formation of polymorph AH-C.

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“…These cases have in common that the structures of the starting phases and the preparation processes are known, but the structures of the end products are difficult to determine because the crystals tend to shatter in the process, leaving nothing but a sample in powder form to work with. Indeed, in these cases the crystal structure of the resulting phase, which is often the phase of interest, must be determined from powder diffraction data Bond et al, 2014;Panda et al, 2014).…”

Section: Introductionmentioning

confidence: 99%