Two novel cocrystals of the N(7)-H tautomeric form of N(6)-benzoyladenine (BA), namely N(6)-benzoyladenine-3-hydroxypyridinium-2-carboxylate (3HPA) (1/1), C12H9N5O·C6H5NO3, (I), and N(6)-benzoyladenine-DL-tartaric acid (TA) (1/1), C12H9N5O·C4H6O6, (II), are reported. In both cocrystals, the N(6)-benzoyladenine molecule exists as the N(7)-H tautomer, and this tautomeric form is stabilized by intramolecular N-H···O hydrogen bonding between the benzoyl C=O group and the N(7)-H hydrogen on the Hoogsteen site of the purine ring, forming an S(7) motif. The dihedral angle between the adenine and phenyl planes is 0.94 (8)° in (I) and 9.77 (8)° in (II). In (I), the Watson-Crick face of BA (N6-H and N1; purine numbering) interacts with the carboxylate and phenol groups of 3HPA through N-H···O and O-H···N hydrogen bonds, generating a ring-motif heterosynthon [graph set R2(2)(6)]. However, in (II), the Hoogsteen face of BA (benzoyl O atom and N7; purine numbering) interacts with TA (hydroxy and carbonyl O atoms) through N-H···O and O-H···O hydrogen bonds, generating a different heterosynthon [graph set R2(2)(4)]. Both crystal structures are further stabilized by π-π stacking interactions.
Keywords: 3-hydroxypyridinium-2-carboxylate; N6-benzoyladenine; cocrystal; dl-tartaric acid; intermolecular hydrogen bonding; stacking interactions; supramolecular architectures.