Crystal Structure of Methylene Blue Citrate

Abstract: The citrate salt of methylene blue), (Mb)(H3Cit) 0.18H2O (where Mb =methylene blue cation and Cit = citrate anion)have been determined by single-crystal X-ray diffraction. MB+cation are is planar and stacked in an antiparallel fashion, exhibiting π–πassociations at a distance of 3.746(6)Å. The Mb+ cation forms a short contacts of the type C-H..O with citric anion through methyl groups of the NMe2 side substituents. Water molecules occupy voids between stacks of MB+ cations with a very low site occupancies and do not form any short contacts with the citric anion.The intermolecular interactionsand specific weak contacts were analyzed by Hirshfeld surface calculations.