Lamotrigine, an antiepileptic drug, and its chloride and nitrate salts.

In lamotrigine [systematic name: 6-(2,3-dichlorophenyl)-1,2,4-triazine-3,5-diamine], C(9)H(7)Cl(2)N(5), (I), the asymmetric unit contains one lamotrigine base molecule. In lamotriginium chloride [systematic name: 3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazin-2-ium chloride], C(9)H(8)Cl(2)N(5)(+).Cl(-), (II), the asymmetric unit contains one lamotriginium cation and one chloride anion, while in lamotriginium nitrate, C(9)H(8)Cl(2)N(5)(+).NO(3)(-), (III), the asymmetric unit contains two crystallographically independent lamotriginium cations and two nitrate anions. In all three structures, N-H...N hydrogen bonds form an R(2)(2)(8) dimer. In (I) and (II), hydrophilic layers are sandwiched between hydrophobic layers in the crystal packing. In all three structures, hydrogen bonds lead to the formation of a supramolecular hydrogen-bonded network. The significance of this study lies in its illustration of the differences between the supramolecular aggregation in the lamotrigine base and in its chloride and nitrate salts.