Multicomponent crystalline solid forms of pyridinecarboxamides and DL-2-Hydroxy-2-phenylacetic acid

We have prepared co-crystals of DL-2-Hydroxy-2-phenylacetic acid (H₂ma) with picolinamide (pic), nicotinamide (nam) and isonicotinamide (inam). They have been characterized by elemental analysis, single crystal and powder X-ray, IR spectroscopy and ¹H and ¹³C NMR. The crystal packing is stabilized primarily by hydrogen bonding and in some cases through π-π stacking interactions. The analysis of crystal structures reveals the existence of the characteristic heterosynthons with the binding motif of the characteristic heterosynthons with the binding motif R22(8) (primary amide-carboxilic acid) between pyridinecarboxamide molecules and the acid. Other synthons involve hydrogen bonds like (carboxyl)O-H···N(pyridine) and (hydroxyl)O-H···N(pyridine).