Crystal structure of levomepromazine maleate

The asymmetric unit of the title salt, C19H25N2OS+center dot C4H3O4- [systematic name: (S)-3-(2-methoxyphenothiazin-10-yl)-N,N,2-trimethylpropanaminium hydrogen maleate], comprises two (S)-levomepromazine cations and two hydrogen maleate anions. The conformations of the two cations are similar. The major difference relates to the orientation of the methoxy substituent at the phenothiazine ring system. The crystal components form a three-dimensional supramolecular network via N-H center dot center dot center dot O, C-H center dot center dot center dot O and C-H center dot center dot center dot pi interactions. A comparison of the conformations of the levomepromazine cations with those of the neutral molecule and similar protonated molecules reveals significant conformational flexibility of the phenothiazine ring system and the substituent at the phenothiazine N atom.