Inclusion of Pentamidine in Carboxylated Pillar[5]arene: Late Sequential Crystallization and Diversity of Host–Guest Interactions

Here we describe the inclusion of minor-groove binding drug pentamidine in its extended conformation into macrocyclic cavity water-soluble carboxylated pillar[5]arene. The artificial host–guest system is manifested as an ensemble three crystalline forms differing pillar[5]arene–pentamidine interaction mode, solvation type, and even stoichiometry. strong hydrogen bonds various types amidinium–carboxylate (between pillar[5]arene) carboxylic–carboxylate adjacent pillar[5]arenes) are realized all complexes, rigidifying assembly. However, it seems that more subtle effects, such local solvation/desolvation, a certain degree flexibility both host guest, variable protonation/deprotonation state pillar[5]arene substituents, play significant roles peculiar crystallization behavior system. snapshots crystal structures highlighting geometries intermolecular modes between same guest present exciting opportunities terms holistic models systems, shifting from focusing our attention on “visible interactions” one structure to appreciation many effects playing combined role chemistry.