BEST-CSP Benchmark Study of Polymorphs I and II of Sulfamerazine and the Perils of Polytype Polymorphs
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Le résumé fourni par la source
High Resolution Image Download MS PowerPoint Slide We report the outcome of an interdisciplinary investigation, by the BEST-CSP network, of the kinetically favored form I and the low-temperature stable form II polymorphs of the drug sulfamerazine (SMZ). Form II can be reproducibly obtained by slurrying in acetonitrile(MeCN)/water at room temperature, though seeding with form II significantly speeds up the conversion. New structure determinations have been obtained for both forms over a wide temperature range, with both single crystal and powder X-ray diffraction methods. Room temperature FT-IR and solid-state 13 C NMR spectra are provided. The enantiotropic but practically irreversible crystal-to-crystal transition from form II to form I is observed at temperatures ranging from 150 to 170 °C in various differential scanning calorimetry (DSC) experiments, depending on sample and heating rate. The enthalpy of transition at 150 °C is measured as Δ trs H m (II → I) = 3.15 ± 0.12 kJ mol –1 . The differences in the heat capacities mean that the DSC measured enthalpies vary with the onset temperature by about 0.55 kJ mol –1 over the range of heating rates commonly used in DSC experiments. Attempts to find the solvent-mediated transition temperature were complicated by observing that slurrying experiments in both methanol and MeCN/H 2 O above 50 °C produce a new, late-identified polymorph, sulfamerazine form V, which is closely related to form I but with an alternative packing of the double layers, i.e., is a polytype polymorph. Forms I and V are only easily distinguishable by high-quality powder X-ray diffraction. Form V appears to be marginally more stable than form I across the temperature range studied. The experimental data, including heat capacities and thermal expansion rates, are used to test a wide range of assumptions and energy models for calculating free energy differences between these polymorphs, illustrating the challenges in computationally modeling the thermodynamic transition temperature between form I and II. The implications of the discovery of form V on establishing the phase diagram of sulfamerazine are discussed.
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Le contrôle bibliographique ouvert
DOI retrouvé dans Crossref DOI retrouvé ; titre concordant.
- Titre Crossref
- BEST-CSP Benchmark Study of Polymorphs I and II of Sulfamerazine and the Perils of Polytype Polymorphs
- Date Crossref
- 12/12/2025
- Éditeur
- American Chemical Society (ACS)
- Type
- journal-article
Ce recoupement confirme des métadonnées liées au DOI. Il ne confirme ni la méthode ni les conclusions de l’étude, et il ne compte pas comme une seconde source scientifique indépendante.
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University College London Department of Chemistry pays non établi dans la noticeUniversité ou école supérieure
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University of Warsaw pays non établi dans la noticeUniversité ou école supérieure
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Czech Academy of Sciences pays non établi dans la noticeOrganisme public
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Department of Chemistry — University College London, University of Warsaw et Czech Academy of Sciences, avec 9 autres affiliations.
Une affiliation ne permet pas de déduire la nationalité d’un auteur.