The conformation of pyrogallol as a result of cocrystallization with N-heterocyclic bases

Structural analysis of the supramolecular cocrystals formed by pyrogallol with acridine, 4,4′-bipyridine, and 1,10-phenanthroline shows that the studied cocrystals are assembled via the hydroxyl-pyridine heterosynthon. In the crystal and molecular structures of these cocrystals in order to form the maximum number of hydrogen bonds, taking into consideration steric effects, the pyrogallol moiety in the supramolecular arrangement has the following conformations: with acridine - syn1, 4,4′-bipyridine - anti, and 1,10-phenanthroline - syn2. Discrete supramolecular complexes are formed by acridine-pyrogallol and the 1,10-phenanthroline-pyrogallol polymorph I. The 1,10-phenanthroline-pyrogallol polymorph II and the 4,4′-bipyridine- pyrogallol trihydrate form extended hydrogen bonded chains.