Syntheses, crystal structures and Hirshfeld surface analyses of four mol-ecular salts of amitriptynol.

The syntheses and crystal structures of four salts of amitriptynol (C 20 H 25 NO) with different carb-oxy-lic acids are described. The salts formed directly from solutions of amitriptyline (which first hydrolysed to amitriptynol) and the cor-responding acid in aceto-nitrile to form amitriptynolium [sys-tem-atic name: (3-{2-hy-droxy-tri-cy-clo[9.4.0.0 3,8 ]penta-deca-1(11),3,5,7,12,14-hexa-en-2-yl}pro-pyl)di-methyl-az-an-ium] 4-meth-oxy-benzoate monohydrate, C 20 H 26 NO + ·C 8 H 7 O 3 - ·H 2 O, ( I ), ami-triptynolium 3,4-di-meth-oxy-benzoate trihydrate, C 20 H 26 NO + ·C 9 H 9 O 4 - ·3H 2 O, ( II ), amitriptynolium 2-chloro-benzoate, C 20 H 26 NO + ·C 7 H 4 ClO 2 - , ( III ), and amitriptynolium thio-phene-2-carboxyl-ate monohydrate, C 20 H 26 NO + ·C 5 H 3 O 2 S - ·H 2 O, ( IV ). Compound ( III ) crystallizes with two cations, two anions and six water mol-ecules in the asymmetric unit. The different conformations of the amitriptynolium cations are determined by the torsion angles in the di-methyl-amino-propyl chains and the -CH 2 -CH 2 - bridge between the benzene rings in the tricyclic ring system, and are complicated by disorder of the bridging unit in II and III . The packing in all four salts is dominated by N-H⋯O and O-H⋯O hydrogen bonds. Hirshfeld surface analyses show that the amitriptynolium cations make similar inter-species contacts, despite the distinctly different packing in each salt.