Syntheses and crystal structures of hydrated and anhydrous 1:2 cocrystals of oxyresveratrol and zwitterionic proline

The hydrated and anhydrous 1:2 cocrystals of oxyresveratrol (4-[(E)-2-(3,5-di-hydroxy-phen-yl)ethen-yl]benzene-1,3-diol; OXY; C₁₄H₁₂O₄) and proline [(S)-pyrrolidine-2-carb-oxy-lic acid; PRO; C₅H₉NO₂], namely, 4-[(E)-2-(3,5-di-hydroxy-phen-yl)ethen-yl]benzene-1,3-diol bis-[(S)-pyrrolidin-1-ium-2-carboxyl-ate] monohydrate, C₁₄H₁₂O₄·2C₅H₉NO₂·H₂O, and the anhydrous form, C₁₄H₁₂O₄·2C₅H₉NO₂, were obtained by crystallization at different temperatures. Both of them crystallize with ortho-rhom-bic (P2₁2₁2₁) symmetry. The structures display N-H⋯O and O-H⋯O hydrogen-bonding inter-actions between PRO and PRO, OXY and OXY, and OXY and PRO. In the hydrated cocrystal, these types of contacts are also observed between the OXY, PRO and water mol-ecules. A combination of these inter-actions leads to a three-dimensional supra-molecular assembly in each case. Hirshfeld surfaces were used to gain further insight into the inter-molecular inter-actions in the packing, including the relative percentage contributions of the significant inter-molecular H⋯H and H⋯O/O⋯H contacts.