Crystal-structure studies of 4-phenyl-piperazin-1-ium 4-eth-oxy-benzoate monohydrate, 4-phenyl-piperazin-1-ium 4-meth-oxy-benzoate monohydrate, 4-phenyl-piperazin-1-ium 4-methyl-benzoate monohydrate and 4-phenyl-piperazin-1-ium tri-fluoro-acetate 0.12-hydrate.

In this study, four new piperazinium salts, namely, 4-phenyl-piperazin-1-ium 4-eth-oxy-benzoate monohydrate, C 9 H 9 O 3 ·C 10 H 15 N 2 ·H 2 O ( I ); 4-phenyl-piperazin-1-ium 4-meth-oxy-benzoate monohydrate, C 10 H 15 N 2 ·C 8 H 7 O 3 ·H 2 O ( II ); 4-phenyl-piperazin-1-ium 4-methyl-benzoate monohydrate, C 10 H 15 N 2 ·C 8 H 7 O 2 ·H 2 O ( III ); and 4-phenyl-piperazin-1-ium tri-fluoro-acetate 0.12 hydrate, C 10 H 15 N 2 ·C 2 F 3 O 2 ·0.12H 2 O ( IV ), have been synthesized. The single-crystal structures of these compounds reveal that all of them crystallize in the triclinic P space group and the crystal packing of ( I )-( III ) is built up of ribbons formed by a combination of hydrogen bonds of type N-H⋯O, O-H⋯O and other weak inter-actions of type C-H⋯O and C-H⋯π, leading to a three-dimensional network. In the crystal of ( IV ), the cations and the anions are connected by C-H⋯O, N-H⋯O and C-H⋯F hydrogen bonds and by C-H⋯π inter-actions, forming sheets which in turn inter-act to maintain the crystal structure by linking through the oxygen atoms of water mol-ecules and van der Waals inter-actions, giving the whole structure.