Cocrystals: Solution, Mechanochemistry, and Sublimation

A systematic study of the effect of crystallization method on the resulting solid-state form of a series of organic cocrystals has been carried out. Cocrystals of p- benzoquinone (BQ) and one of four monosubstituted p- halophenols were made by crystallization from chloroform, cosublimation in vacuo, and neat grinding. Cocrystals with both 1:1 and 2:1 donor–acceptor ratios can be prepared from all four BQ–halophenol combinations. Here we report the preparation of four new cocrystals of BQ with either 4-fluorophenol or 4-iodophenol. In the case of the 1:1 4-fluorophenol–BQ cocrystal, different polymorphs were isolated by recrystallization from solution and cosublimation. Sublimation is shown to be an important technique in accessing the phase space of cocrystals.