Abstract The crystals of a 1:1 complex of 1,2-bis(diethylaminomethyl)-4,5-dichlorobenzene perchlorate with HClO 4 were studied using X-ray diffraction and FT-IR spectroscopy. There are two symmetry-independent ionic pairs in the crystal, monoclinic, space group P2 1/ n. In both symmetry-independent cations, the diethylaminomethyl substituents are in a similar Z conformation relative to the phenyl moieties, however significant conformational differences in the diethylaminomethyls have been noted. The diethylaminomethyls are linked by intracationic +N–H⋯N hydrogen bonds of 2.758(9) and 2.721(7) Å in two symmetry-independent cations. The protons in these H-bonds are disordered in two off-center sites, which is most likely to be connected with the considerable disorder of the perchlorate anions. The IR spectrum of the crystals shows a broad intense band and a relatively intense continuous absorption indicating relatively large proton polarizability in the intramolecular hydrogen bond of a medium length.