N-[2-(4-hydroxybenzylideneamino)ethyl]-N-[2-(4-oxidobenzylideneamino)ethyl]ammonium

The title Schiff base compound, C18H21N3O2, was synthesized by a condensation reaction of 4-hydroxybenzaldehyde with diethylenetriamine. The crystal structure determination reveals that one of the terminal hydroxy groups is deprotonated while the imino group of the molecule is protonated; thus the compound is a zwitterion. The two terminal benzene rings are nearly parallel to one another, with a dihedral angle of 9.94 (6)degrees. Intermolecular O-H center dot center dot center dot O and N-H center dot center dot center dot O hydrogen bonding helps to stabilize the crystal structure.