Quetiapine N-oxide–fumaric acid (2/1)

The title compound (systematic name: 2-{2-[4-(dibenzo[b,f][1,4]thia­zepin-11-yl)piperazin-1-yl 1-oxide]eth­oxy}ethanol–fumaric acid (2/1)), C(21)H(25)N(3)O(3)S·0.5C(4)H(4)O(4), is one of the oxidation products of quetiapine hemifumaric acid. In the tricyclic fragment, the central thia­zepine ring displays a boat conformation and the benzene rings are inclined to each other at a dihedral angle of 72.0 (2)°. The piperazine ring adopts a chair conformation with its eth­oxy­ethanol side chain oriented equatorially. In addition to the main mol­ecule, the asymmetric unit contains one-half mol­ecule of fumaric acid, the complete mol­ecule being generated by inversion symmetry. In the crystal, O—H⋯O hydrogen bonds link the components into corrugated layers parallel to bc plane.