Exploring the hydrogen-bond preference of N–H moieties in co-crystals assembled via O–H(acid)⋯N(py) intermolecular interactions

In order to establish the hydrogen-bond preference of an amide based N–H moiety faced with different CO or –OH hydrogen-bond acceptors, the crystal structures of several new co-crystals and salts were examined: 3-acetaminopyridine fumaric acid (2 : 1) 1, 4-(acetaminomethyl)pyridine fumaric acid (2 : 1) 2, 4-acetaminopyridine decanedioic (sebacic) acid (2 : 1) 3, 4-(acetaminomethyl)pyridine adipic acid (2 : 1) 4, 4-(acetaminomethyl)pyridine isophthalic acid (2 : 1) 5, 4-(acetaminomethyl)pyridinium 5-nitro-hydrogen isophthalate hydrate 6, 4-acetaminopyridinium hydrogenglutarate (1 : 1) 7. All co-crystals, 1–5, are constructed from an O–H(acid)⋯N(py) hydrogen bond and for the salts, 6–7, the primary synthon is the corresponding charge-assisted N–H+⋯−O interaction. The remaining N–H donor (on the amide moiety) shows a preference (4 out of 5) for the amide CO over the acid CO.