Synthesis and structure of clozapine N-oxide hemi(hydrochloride): an infinite hydrogen-bonded poly[n]catenane

The structure of the title compound, 2C18H19ClN4O·HCl or (CNO)2·HCl (C36H39Cl3N8O2), at 100 K has tetragonal (I4/m) symmetry. The dihedral angle between the benzene rings of the fused ring system of the CNO molecule is 40.08 (6)° and the equivalent angle between the seven-membered ring and its pendant N-oxide ring is 31.14 (7)°. The structure contains a very strong, symmetrical O—H...O hydrogen bond [O...O = 2.434 (2) Å] between two equivalent R3N+—O− moieties, which share a proton lying on a crystallographic twofold rotation axis. These units then form a (CNO)4·(HCl)2 ring by way of two equivalent N—H...Cl hydrogen bonds (Cl− site symmetry m). These rings are catenated into infinite chains propagating along the c-axis direction by way of shape complementarity and directional C—H...N and C—H...π interactions.