Structure of the Caffeine-Pyrogallol Complex: Revisiting a Pioneering Structural Analysis of a Model Pharmaceutical Cocrystal

Abstract

The 1967 attempt of structural analysis of the solid-state complex of caffeine and pyrogallol was a pioneering structural investigation in supramolecular chemistry of caffeine, of what today would easily be considered an archetype of a model pharmaceutical cocrystal. Re-investigating this historically important system demonstrates that this long overlooked complex is most likely a tetrahydrate with a different structure and composition than initially proposed, and provide the crystal structure of the anhydrous cocrystal.