Abstract: | 4‐Hydroxypyridine and terephthalic acid cocrystallize as a hydrate, 4‐pyridone–terephthalic acid–water (2/1/2), 2C5H5NO·C8H6O4·2H2O, from a methanol–water solution. The molecules form a two‐dimensional hydrogen‐bonded network resulting in sheets of hydrogen‐bonded molecules that lie parallel to the (10) plane. In contrast, 3‐hydroxypyridine and terephthalic acid form the salt bis(3‐hydroxypyridinium) terephthalate, 2C5H6NO+·C8H4O42−, giving rise to two‐dimensional hydrogen‐bonded sheets extending through the lattice parallel to the (10) plane. |