Syntheses and crystal structures of 4-(4-meth-oxy-phen-yl)piperazin-1-ium 4-methyl-benzoate monohydrate and bis-[4-(4-meth-oxy-phen-yl)piperazin-1-ium] benzene-1,2-di-carboxyl-ate

Abstract

Co-crystallization of N-(4-meth-oxy-phen-yl)piperazine with 4-methyl-benzoic acid and with benzene-1,2-di-carb-oxy-lic acid yields the salts 4-(4-meth-oxy-phen-yl)piperazin-1-ium 4-methyl-benzoate monohydrate, C₁₁H₁₇N₂O⁺·C₈H₇O₂ ^-·H₂O (I), and bis-[4-(4-meth-oxy-phen-yl)piperazin-1-ium] benzene-1,2-di-carboxyl-ate, 2C₁₁H₁₇N₂O⁺·C₈H₄O₄ ^2- (II). These salts both crystallize with Z' = 2, in space groups P and Pna2₁, respectively. In compound (I), a combination of four O-H⋯O, four N-H⋯O, one C-H⋯O and one C-H⋯π(arene) hydrogen bonds link the six independent components into complex sheets, within which the two piperazine rings, the two anions, and the two water mol-ecules are related by an approximate, non-crystallographic translation along the b-axis direction. In compound (II), sheets containing R ⁴ ₄(18) and R ¹⁰ ₁₂(38) rings are formed by the combined action of eight independent N-H⋯O hydrogen bonds. Comparisons are made with the structures of some related compounds.

Keywords: co-crystallization; crystal structure; hydrogen bonding; mol­ecular structure; piperazine; supra­molecular assembly; twinning by inversion.