Syntheses, crystal structures and Hirshfeld surface analysis of 4-(4-nitro-phen-yl)piperazin-1-ium tri-fluoro-acetate and 4-(4-nitro-phen-yl)piperazin-1-ium tri-chloro-acetate.

The synthesis and crystal structures of the mol-ecular salts of 4-(4-nitro-phen-yl)piperazine with tri-fluoro-acetate, namely, 4-(4-nitro-phen-yl)piperazin-1-ium tri-fluoro-acetate, CHNO ·CFO (I), and with tri-chloro-acetate, namely, 4-(4-nitro-phen-yl)piperazin-1-ium tri-chloro-acetate, CHNO ·CClO , (II), are reported and compared. A partial positional disorder of the anions was found. In both structures, the piperazine rings adopt a chair conformation, whereas the positions of the nitro-phenyl group on the piperazine ring differ from bis-ectional in (I) to equatorial in (II). In both structures, the supra-molecular assemblies are mono-periodic on the basis of the chain-of-rings motifs supported by aromatic π-π inter-actions. Hirshfeld surface analysis was used to explore the inter-molecular close contacts in both crystals. The most dominant contacts of the Hirshfeld surface of the cation-anion pairs of the asymmetric units are O⋯H/H⋯O, and those with a contribution of halogen atoms: F⋯H/H⋯F in (I) and Cl⋯H/H⋯Cl in (II), respectively.