Surface Analysis-From Crystal Structures to Particle Properties.

Understanding the surface properties of particles is crucial for optimizing the performance of formulated products in various industries. However, acquiring this understanding often requires expensive trial-and-error studies. Here, we present advanced surface analysis tools that enable the visualization and quantification of chemical and topological information derived from crystallographic data. By employing functional group analysis, roughness calculations, and statistical interaction data, we facilitate direct comparisons of surfaces. We further demonstrate the practicality of our approach by correlating the sticking propensity of distinct ibuprofen morphologies with surface and particle descriptors calculated from a single crystal structure. Our findings support and expand upon previous work, demonstrating that the presence of a carboxylic acid group on the {011} facet leads to significant differences in particle properties and explains the higher electrostatic potential observed in the block-like morphology. While our surface analysis tools are not intended to replace the importance of chemical intuition and expertise, they provide valuable insights for formulators and particle engineers, facilitating informed, data-driven decisions to mitigate formulation risks. This research represents a significant step toward a comprehensive understanding of particle surfaces and their impact on products.

Exploring the CSD Drug Subset: An Analysis of Lattice Energies and Constituent Intermolecular Interactions for the Crystal Structures of Pharmaceuticals.

Intermolecular (synthonic) modelling is used for a statistical analysis of crystal lattice energies, together with their contributing intermolecular interactions for the crystallographic structures selected from the CCDC's Drug Subset (https://doi.org/10.1016/j.xphs.2018.12.011). Analysis of this selected subset reveal similarities in packing compared to other organic crystals in the CSD with linear relationships between molecular weight and unit cell volume, void space, and packing coefficient. Crystal lattice energy calculations converge within a 30 Šintermolecular radius characterised by a mean lattice energy of ca. -36 kcal mol-1 with ca. 85% and 15% due to dispersive and electrostatic interactions, respectively. The distribution of the strongest synthons within the individual structures reveals an average strength of -5.79 kcal mol-1. The diversity of chemical space within the drug molecules is in agreement with the analysis of atom types across the selected subset with phenyl groups being found to contribute the highest mean energy of -11.28 kcal mol-1, highlighting the importance of aromatic interactions within pharmaceutical compounds. Despite an initial focus on Z' = 1 structures, this automated approach enables rapid and consistent quantitative analysis of lattice energy, synthon strength and functional group contributions, providing solid-form informatics for pharmaceutical R&D and a helpful basis for further investigations.

Crystallographic Structure, Intermolecular Packing Energetics, Crystal Morphology and Surface Chemistry of Salmeterol Xinafoate (Form I).

Single crystals of salmeterol xinafoate (form I), prepared from slow cooled supersaturated propan-2-ol solutions, crystallize in a triclinic P1¯ symmetry with 2 closely related independent salt pairs within the asymmetric unit, with an approximately double-unit cell volume compared with the previously published crystal structure. Synthonic analysis of the bulk intermolecular packing confirms the similarity in packing energetics between the 2 salt pairs. The strongest synthons, as expected, are dominated by coulombic interactions. Morphologic prediction reveals a plate-like morphology, dominated by the {001}, {010}, and {100} surfaces, consistent with experimentally grown crystals. Although surface chemistry of the slow-growing {001} face comprises large sterically hindering phenyl groups, although weaker coulombic interactions still prevail from the alcohol group present on the phenyl and hydroxymethyl groups. The surface chemistry of the faster growing {010} and {100} faces are dominated by the significantly stronger cation/anion interactions occurring between the carboxylate and protonated secondary ammonium ion groups. The importance of understanding the cohesive and adhesive nature of the crystal surfaces of an active pharmaceutical ingredient, with respect to their interaction with other active pharmaceutical ingredient crystals and how that may affect formulation design, is highlighted.