Six 1-aroyl-4-(4-meth-oxy-phen-yl)piperazines: similar mol-ecular structures but different patterns of supra-molecular assembly.

Six new 1-aroyl-4-(4-meth-oxy-phen-yl)piperazines have been prepared, using coupling reactions between benzoic acids and N-(4-meth-oxy-phen-yl)piperazine. There are no significant hydrogen bonds in the structure of 1-benzoyl-4-(4-meth-oxy-phen-yl)piperazine, C18H20N2O2, (I). The mol-ecules of 1-(2-fluoro-benzo-yl)-4-(4-meth-oxy-phen-yl)piperazine, C18H19FN2O2, (II), are linked by two C-H⋯O hydrogen bonds to form chains of rings, which are linked into sheets by an aromatic π-π stacking inter-action. 1-(2-Chloro-benzo-yl)-4-(4-meth-oxy-phen-yl)piperazine, C18H19ClN2O2, (III), 1-(2-bromo-benzo-yl)-4-(4-meth-oxy-phen-yl)piperazine, C18H19BrN2O2, (IV), and 1-(2-iodo-benzo-yl)-4-(4-meth-oxyphen-yl)piperazine, C18H19IN2O2, (V), are isomorphous, but in (III) the aroyl ring is disordered over two sets of atomic sites having occupancies of 0.942 (2) and 0.058 (2). In each of (III)-(V), a combination of two C-H⋯π(arene) hydrogen bonds links the mol-ecules into sheets. A single O-H⋯O hydrogen bond links the mol-ecules of 1-(2-hy-droxy-benzo-yl)-4-(4-meth-oxy-phen-yl)piperazine, C18H20N2O3, (VI), into simple chains. Comparisons are made with the structures of some related compounds.