A polymorph of N'-[(4-hy-droxy-phen-yl)methyl-idene]pyridine-4-carbohydrazide.

The synthesis and single-crystal X-ray diffraction analysis of a polymorphic form of the isoniazid derivative N'-[(4-hy-droxy-phen-yl)methyl-idene]pyridine-4-carbohydrazide, C13H11N3O2, are reported, revealing that both the mol-ecular conformation and the hydrogen-bonding scheme differ in the two polymorphs. The crystal packing of the title polymorph is primarily consolidated by N-H⋯O and O-H⋯N hydrogen-bonding inter-actions, leading to the formation of a supra-molecular layer parallel to (001). The inter-molecular contacts were further qu-anti-fied and analysed using Hirshfeld surface analysis.