Pyridoxal Isonicotinoyl Hydrazone (PIH), a Synthetic Ion‐Chelating Agent

Pyridoxal isonicotinoyl hydrazone [3-hydroxy-5-(hydroxymethyl)-2-methyl-4-pyridinecarboxaldehyde-4-pyridinecarbonylhydrazone, C 14 H 14 N 4 O 3 ] exibits a non-planar conformation. Non-H atoms lie almost in two planes, one of the isonicotinoyl ring, the other of the remainder of the molecule, with a dihedral angle of 17.41° between them. The central C=N-N'-C=O chain has an E configuration around the C=N double bond of the hydrazone bridge, a trans motif of the amide group along -N'-C= and an S-trans conformation along the N-N' bond. This geometry allows intramolecular hydrogen bonding between the hydrazone N atom and the 3-hydroxy group.