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.
Highlights
Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag, PO WITS, 2050, The crystal structures of seven ammonium carboxylate salts are reported, namely (RS)-1-phenylethan-1-aminium isonicotinate, C8H12N+ÁC6H4N1O2À, (I), (RS)-1-phenylethan-1-aminium flurbiprofenate [or 2-(3-fluoro-4-phenylphenyl)propanoate], C8H12N+ÁC15H12FO2À, (II), (RS)-1-phenylethan-1-aminium 2-chloro-4-nitrobenzoate, C8H12N+ÁC7H3ClNO4À, (III), (RS)-1-phenylethan-1aminium 4-iodobenzoate, C8H12N+ÁC7H4IO2À, (IV), (S)-1-cyclohexylethan-1aminium 2-chloro-4-nitrobenzoate, C8H18N+ÁC7H3ClNO4À, (V), 2-(cyclohex-1en-1-yl)ethan-1-aminium 4-bromobenzoate, C8H16N+ÁC7H4BrO2À, (VI), and (S)-1-cyclohexylethan-1-aminium 4-bromobenzoate, C8H18N+ÁC7H4BrO2À, (VII)
Salt (I) has a unique hydrogen-bonded system of ladders, featuring both N+— HÁ Á ÁOÀ and N+—HÁ Á ÁN hydrogen bonds owing to the presence of the pyridine functional group
The presence of an additional hydrogen-bond acceptor on the carboxylate cation disrupts the formation of the ubiquitous type II and III ladder found predominately in ammonium carboxylate salts
Summary
The conception and synthesis of molecular solid-state structures, is fundamentally based upon the discernment and subsequent exploitation of intermolecular interactions. We have investigated the effects thereof of changing both the structure and stereochemistry of the constituents on the robust ionic supramolecular heterosynthons generated by ammonium carboxylate salts (R–NH3+)Á(R–COOÀ), where R often contains a phenylethyl group generating chiral molecules (Kinbara et al, 1996). It is known from a wide variety of structural studies that ammonium carboxylate salts predom-. The robustness and perturbation of these ladders as a function of the structure and stereochemistry of the constituent ions have been tested via the crystallization of a variety of ammonium carboxylate salts.
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