An investigation to elucidate the factors dictating the crystal structure of seven ammonium carboxyl-ate mol-ecular salts

Abstract

The crystal structures of seven ammonium carboxyl-ate salts are reported, namely (RS)-1-phenyl-ethan-1-aminium isonicotinate, C₈H₁₂N⁺·C₆H₄N₁O₂^-, (I), (RS)-1-phenyl-ethan-1-aminium flurbiprofenate [or 2-(3-fluoro-4-phenyl-phen-yl)propano-ate], C₈H₁₂N⁺·C₁₅H₁₂FO₂^-, (II), (RS)-1-phenyl-ethan-1-aminium 2-chloro-4-nitro-benzoate, C₈H₁₂N⁺·C₇H₃ClNO₄^-, (III), (RS)-1-phenyl-ethan-1-aminium 4-iodo-benzoate, C₈H₁₂N⁺·C₇H₄IO₂^-, (IV), (S)-1-cyclo-hexyl-ethan-1-aminium 2-chloro-4-nitro-benzoate, C₈H₁₈N⁺·C₇H₃ClNO₄^-, (V), 2-(cyclo-hex-1-en-1-yl)ethan-1-aminium 4-bromo-benzoate, C₈H₁₆N⁺·C₇H₄BrO₂^-, (VI), and (S)-1-cyclo-hexyl-ethan-1-aminium 4-bromo-benzoate, C₈H₁₈N⁺·C₇H₄BrO₂^-, (VII). Salts (II) to (VII) feature three N⁺-H⋯O^- hydrogen bonds, which form one-dimensional hydrogen-bonded ladders. Salts (II), (III), (IV), (V) and (VII) have a type II ladder system despite the presence of halogen bonding and other inter-molecular inter-actions, whereas (VI) has a type III ladder system. Salt (I) has a unique hydrogen-bonded system of ladders, featuring both N⁺-H⋯O^- and N⁺-H⋯N hydrogen bonds owing to the presence of the pyridine functional group. The presence of an additional hydrogen-bond acceptor on the carboxyl-ate cation disrupts the formation of the ubiquitous type II and III ladder found predominately in ammonium carboxyl-ate salts. Halogen bonding, however, has no influence on their formation.

Keywords: ammonium carboxyl­ate salts; crystal structure; graph set; hydrogen bonding.