New building blocks for crystal engineering. Syntheses and crystal structures of oxime-substituted pyridines

The syntheses and crystal structures of a family of oxime-substituted pyridine ligands [py-C(R)NOH, where R = H, Me, Ph, or NH2] are presented. The compounds are all prepared in good yields by allowing a suitably substituted pyridine to react with hydroxylamine. Their solid-state structures show that the dominating hydrogen bond, a head-to-tail O-H center dot center dot center dot N interaction between the oxime O-H moiety and the pyridine nitrogen atom, is present in each of the seven reported cases. This intermolecular interaction generates infinite chains that are crosslinked into 2D or 3D assemblies by weaker C-H center dot center dot center dot N or C-H center dot center dot center dot O hydrogen bonds.