Crystal Structures and Thermodynamic Properties of New Atypical Antipsychotic Cariprazine and Its Hydrochloride

A cariprazine, an oral atypical antipsychotic acting as a D2 and D3 receptor partial agonist, has been crystallized as a free base, trans-N-{4-[2-[4-(2,3-dichlorophenyl)piperazine-1-yl]ethyl]cyclohexyl}-N',N'-dimethylurea, C21H32Cl2N4O (I), and as a chloride salt, trans-N-{4-[2-[4-(2,3-dichlorophenyl)piperazine-1-yl]ethyl]cyclohexyl}-N',N'-dimethylurea hydrochloride, C21H33Cl2N4O+Cl- (II). In both structures, the cariperazine molecule is in an extended conformation. The dimethylurea group exhibits a syn conformation of the O atoms in the I, whereas an almost anti orientation is present in the II. Two terminal groups, dimethylurea and dichlorophenyl ring, are oriented differently in the I and II. The cariprazine molecules in the I are linked into an infinite zigzag chains by N-HO hydrogen bonds, where the neighboring cariprazine molecules form an L-shape configuration. In the II, the molecules of cariprazine are connected with the chloride anion by N-HCl charge-assisted hydrogen bonds, which are further stabilized by weak intermolecular interactions, forming horizontal molecular chain along the b axis. This study reveals the variations in the solid-state conformation of cariprazine molecule in different crystalline environments.