Multicomponent Crystalline Solid Forms of Pyridinecarboxamides and DL-2-Hydroxy-2-phenylacetic Acid

Abstract

We have prepared co-crystals of racemic DL-2-Hydroxy-2-phenylacetic acid (DL-Mandelic acid, DL-H2ma) with achiral 2-Pyridinecarboxamide (picolinamide, pic), 3-Pyridinecarboxamide (nicotinamide, nam), and 4-Pyridinecarboxamide (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 R22(8) (primary amide-carboxilic acid) between pyridinecarboxamide molecules and the acid. Other synthons involve hydrogen bonds such as (carboxyl)O-H···N(pyridine) and (hydroxyl)O-H···N(pyridine).

Keywords

• pyridinecarboxamides
• cocrystals
• mandelic acid