Crystalline Forms of Trazodone Dihydrates

Michael Plater* (Corresponding Author), William Harrison

*Corresponding author for this work

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In this study, treatment of anhydrous trazodone powder with ammonium carbamate in warm water crystallised two new polymorphs or dihydrates of trazodone after 5 h, whose structures were determined by X-ray single crystal diffraction. Each dihydrate contains infinite zigzag hydrogen- bonded chains of water molecules, which are stabilised by the N4 acceptor atom of the piperazine ring and the pendant carbonyl O1 atom of the triazole ring, as well as other water molecules. The strong dipole moment expected for the O1 atom makes it a good hydrogen bond acceptor for stabilising the chains of water molecules. Each molecule of trazodone has a similar conformation in both hydrates, except for the propyl chains, which adopt different conformations: anti-gauche in the β hydrate (triazole N-C-C-C and C-C-C-piperazine N) and anti-anti in the γ hydrate. Both piperazine rings adopt chair conformations, and the exocyclic N-C bonds are in equatorial orientations. The Hirshfeld surfaces and two-dimensional fingerprint plots for the polymorphs were calculated using CrystalExplorer17, which indicated contacts significantly shorter than the sum of the van der Waals radii in the vicinity of the piperazine N4 and triazole O1 atoms corresponding to the strong hydrogen bonds accepted by these atoms.
Original languageEnglish
Article number5361
Number of pages11
Publication statusPublished - 3 Sept 2021

Bibliographical note

Funding: This research received no external funding.
Acknowledgments: We thank the University of Aberdeen Development Trust for funding to MJP, and the EPSRC National Crystallography Service (University of Southampton) for the X-ray data collections.


  • trazodone
  • crystalline hydrate
  • polymorph
  • crystallography


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