The title mol-ecular salt, C10H13N2 +·C2H3O2 -·0.5H2O, crystallized with four 2-(1H-indol-3-yl)ethanaminium cations (A, B, C and D) and four acetate anions in the asymmetric unit, together with two water mol-ecules of crystallization. Each cation is linked to an anion by a C-H⋯π inter-action. The alkyl-aminium side chains have folded conformations, with N-C-C-C torsion angles of -58.5 (3), 59.5 (3), -64.6 (3) and -56.0 (3)° for cations A, B, C and D, respectively. In the crystal, the cations and anions are liked by N-H⋯O and C-H⋯O hydrogen bonds, forming chains propagating along the b-axis direction. The chains are linked by the water mol-ecules via Owater-H⋯O and N-H⋯Owater hydrogen bonds, forming layers lying parallel to the bc plane. The overall inter-molecular inter-actions were investigated using Hirshfeld surfaces analysis.
Keywords: 2-(1H-indol-3-yl)ethanaminium; Hirshfeld surface analysis; acetate; crystal structure; hydrogen bonding; trypamine.