3-Chloro-4-hydroxyphenylacetic acid co-crystals with nicotinamide, isonicotinamide, phenazine and 4,40-bipyridine: An investigation of synthon motifs

Abstract

Multicomponent crystals of 3-chloro-4-hydroxyphenylacetic acid (CHPAA) with nicotinamide (NAM), isonicotinamide (INAM), phenazine (PHZN) and 4,4′-bipyridine (BIPY) have been successfully synthesised by the slow evaporation technique. The co-crystals were characterised using X-ray diffraction, thermal analysis, FTIR spectroscopy and Hirshfeld surface analysis. Both NAM and INAM co-crystal structures exhibited O–H⋯N and N–H⋯O interactions. Interestingly the INAM co-crystal structure demonstrated the tetrameric amide homosynthon. The incorporation of water into the NAM co-crystal structure resulted in additional O–H⋯O hydrogen bonds. PHZ and BIPY co-crystal structures displayed O–H⋯N interactions. The 2CHPAA•BIPY structure also showed an interesting CHPAA dimer with a head to tail motif characterised by O–H⋯O and formed a hydrogen bonded ring described as . Weaker interactions of the type C–H⋯O, C–H⋯Cl and π … π stacking were also observed in the crystal structures. Alternate preparation methods such as grinding and slurry experiments were also explored.