A structural comparison of salt forms of dopamine with the structures of other phenylethylamines

Alan R. Kennedy, Laura Cruickshank, Pamela Maher, Zoe McKinnon

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The structures of four salt forms of dopamine are reported. These are dopamine [2‐(3,4‐dihydroxyphenyl)ethan‐1‐aminium] benzoate, C8H12NO2+·C7H5O2−, I, dopamine 4‐nitrobenzoate, C8H12NO2+·C7H4NO4−, II, dopamine ethanedisulfonate, 2C8H12NO2+·C2H4O6S22−, III, and dopamine 4‐hydroxybenzenesulfonate monohydrate, C8H12NO2+·C6H5O4S−·H2O, IV. In all four structures, the dopamine cation adopts an extended conformation. Intermolecular interaction motifs that are common in the salt forms of tyramine can be found in related dopamine structures, but hydrogen bonding in the dopamine structures appear to be more variable and less predictable than for tyramine. Packing analysis discovered three dopamine‐containing groups of structures that can be described as isostructural with regards to the cation positions. Two of these groups contain both dopamine and tyramine species, and one of these is also highly variable in other ways too, containing anhydrous and hydrated forms, different anion types and ionized and neutral phenylethylamine species. As such, the group illustrates that packing behaviour can be robust and similar even where intermolecular interactions such as hydrogen bonds are very different.
Original languageEnglish
Pages (from-to)386-394
Number of pages9
JournalActa Crystallographica Section C: Structural Chemistry
Issue numberPart 10
Early online date18 Sept 2023
Publication statusPublished - 31 Oct 2023


  • dopamine
  • phenylethylamine
  • form selection
  • API
  • active pharmaceutical ingredient
  • crystal structure
  • salt selection


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