Synthesis and structural characterization of organic co-crystals 4,4′-bipyridine-bis(N-phenylanthranilic acid) and 4,4′-bipyridinium bis(3-carboxypyridine-2-carboxylate)

Two organic co-crystals namely, 4,4′-bipyridine-bis(N-phenylanthranilic acid) (1) and 4,4′-bipyridinium bis(3-carboxypyridine-2-carboxylate) (2) have been synthesized and studied by FT-IR, TGA/DTA, and single crystal XRD studies. The crystal system of co-crystal 1 is triclinic with space group P1 and Z = 4 and that of co-crystal 2 is monoclinic with space group P21/n and Z = 2. Intermolecular hydrogen bonds, OH⋯N, with graph set designator D22 (10) play a vital role in the formation of the co-crystal 1. Intramolecular hydrogen bond S(6) is also present in 1 and there is no π–π interaction. Whereas in co-crystal 2, the intermolecular hydrogen bonds NH⋯N with graph set designator D22 (12), OH⋯O with graph set designator D, and the π–π interactions together play a major role in stabilizing the structure.

► Both intermolecular and intramolecular hydrogen bonds are present in (1).
► Strong hydrogen bonds NH⋯N and OH⋯O are present in (2).
► π–π interactions are present in (2) but not in (1).