Six 1-halobenzoyl-4-(2-methoxyphenyl)piperazines having Z′ values of one, two or four; Disorder, pseudosymmetry, twinning and supramolecular assembly in one, two or three dimensions

Abstract

Six 1-halobenzoyl-4-(2-methoxyphenyl)piperazines have been prepared using carbodiimide-mediated coupling reactions between halobenzoic acids and N-(2-methoxyphenyl)piperazine. The molecules of 1-(4-fluorobenzoyl)-4-(2-methoxyphenyl)piperazine, C18H19FN2O2 (I), are linked into a chain of rings by a combination of C - H⋯O and C - H⋯π(arene) hydrogen bonds. 1-(4-Chlorobenzoyl)-4-(2-methoxyphenyl)piperazine, C18H19ClN2O2 (II), crystallizes in the space group Pca21 with Z′ = 4 and it exhibits both pseudosymmetry and inversion twinning: a combination of six C - H⋯O and two C - H⋯π(arene) hydrogen bonds generate a three-dimensional assembly. In 1-(4-bromobenzoyl)-4-(2-methoxyphenyl)piperazine, C18H19BrN2O2 (III), which also crystallizes in space group Pca21 but with Z′ = 2, the bromobenzoyl unit in one of the molecules is disordered. Pseudosymmetry and inversion twinning are again present, and a combination of three C - H⋯O and one C - H⋯π(arene) hydrogen bonds generate a two-dimensional assembly. A single C - H⋯O hydrogen bond links the molecules of 1-(4-iodobenzoyl)-4-(2-methoxyphenyl)piperazine, C18H19IN2O2 (IV), into simple chains but in the isomeric 3-iodobenzoyl analogue (V), which crystallizes in space group P212121 with Z′ = 2, a two-dimensional assembly is generated by a combination of four C - H⋯O and two C - H⋯π(arene) hydrogen bonds; pseudosymmetry and inversion twinning are again present. A single C - H⋯O hydrogen bond links the molecules of 1-(2-fluorobenzoyl)-4-(2-methoxyphenyl)piperazine, C18H19FN2O2 (VI), into simple chains. Comparisons are made with the structures of some related compounds.