Royal Society of Chemistry, CrystEngComm, 26(16), p. 5897-5904, 2014
DOI: 10.1039/c4ce00367e
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Haloprogin is a topical antifungal agent. Its structure does not contain any of the functional groups typically exploited in hydrogen bond based co-crystal design. On the other hand, its 1-iodoalkyne moiety is nicely tailored to a crystal engineering strategy based on halogen bonding. Here we describe the formation of three polymorphs of haloprogin and of three co-crystals that this active pharmaceutical ingredient forms with both neutral and ionic co-crystal formers. The halogen bond plays a major role in all of the six structures and the interaction is thus confirmed to be a valuable tool which may complement the hydrogen bond when polymorphs and co-crystals of active pharmaceutical ingredients are pursued.