Partial charge transfer in the salt co-crystal of l -ascorbic acid and 4,4′-bipyridine

In the title 1:2 co-crystal, C₁₀ H₉ N₂⁺ ·(C₆ H_7.75 O₆ ·C₆ H_7.25 O₆) -, l-ascorbic acid (LAA) and 4,4′-bipyridine (BPy) co-crystallize in the chiral space group P2 1 with two molecules of LAA, and one molecule of bpy in the asymmetric unit. The structure was modeled in two parts due to possible proton transfer from LAA to the corresponding side of the bpy molecule having an occupancy of approximately 0.25 and part 2 with an occupancy of approximately 0.75. In this structure, LAA forms hydrogen bonds with neighboring LAA molecules, forming extended sheets of LAA molecules which are bridged by bpy molecules. A comparison to a related and previously published co-crystal of LAA and 3-bromo-4-pyridone is presented.