Hydrogen bonds and π–π inter­actions in two new crystalline phases of methyl­ene blue

摘要: Two unprecedented solid phases involving the 3,7-bis­(di­methyl­amino)­pheno­thia­zin-5-ium cation, i.e. methyl­ene blue (MB+), have been obtained and structurally characterized. In crystals of chloride dihydrate, C16H18N3S+·Cl−·2H2O (I) 3,7-bis­(di­methyl­amino)­pheno­thia­zinium bis­ulfite, C16H18N3S+·HSO4− (II), cationic dye mol­ecules are planar disposed in an anti­parallel mode, showing π–π stacking inter­actions, with mean inter­planar distances 3.326 (4) 3.550 (3) A respectively. compound (I), whose phase was found affected by merohedral twinning [BASF = 0.185 (3)], presence water allows a network hydrogen bonds MB+ as both donor acceptor, whereas homo-inter­action anions causes effective absence classical hydrogen-bond donors. This substantial difference has important consequences for geometry supra­molecular inter­actions cations, which analysed Hirshfeld fingerprint plots subsequently discussed.