Crystal structure of pharmaceutical cocrystals of 2,6‐diaminopyridine with piracetam and theophylline

Pharmaceutical cocrystals are crystalline solids formed by an active pharmaceutical ingredient and a cocrystal former. The cocrystals 2,6-di­amino­pyridine (DAP)–piracetam [PIR; systematic name: 2-(2-oxopyrrolidin-1-yl)acetamide] (1/1), C5H7N3·C6H10N2O2, (I), and 2,6-di­amino­pyridine–theophylline (TEO; systematic name: 1,3-dimethyl-7H-purine-2,6-dione) (1/1), C5H7N3·C7H8N4O2, (II), were prepared by the solvent-assisted grinding method and were characterized by IR spectroscopy and powder X-ray diffraction. Cocrystal (I) crystallized in the ortho­rhom­bic space group Pbca and showed a 1:1 stoichiometry. The DAP and PIR molecules are linked by an N—H⋯O hydrogen-bond inter­action. Self-assembly of PIR mol­ecules forms a sheet of C(4) and C(7) chains. Cocrystal (II) crystallized in the monoclinic P21/c space group and also showed a 1:1 stoichiometry. The DAP and TEO molecules are connected by N—H⋯N and N—H⋯O hydrogen bonds, forming an R22(9) heterosynthon. A bidimensional supra­molecular array is formed by inter­linked DAP–TEO tetra­mers, producing a two-dimensional sheet.