Substituent Effects on the Crystal Structures of Salts Prepared from (R)-2-Methoxy-2-(1-naphthyl)-propanoic Acid and (R)-1-Arylethylamines

The crystal structures of salts 6-9 prepared from (R)-2-methoxy-2-(1-naphthyl)propanoic acid [(R)-M alpha NP acid, (R)-1] and (R)-1-arylethylamines [salt 6, (R)-1-(4-methoxyphenyl)ethylamine.(R)-1; salt 7, (R)-1-(4-fluorophenyl)ethylamine.(R)-1; salt 8, (R)-1-(4-chlorophenyl)ethylamine.(R)-1; and salt 9, (R)-1-(3-chlorophenyl)ethylamine.(R)-1] were elucidated by X-ray crystallography. The solid-state associations and conformations of the M alpha NP salts were defined using the concepts of supramolecular- and planar chirality, respectively, and the crystal structures of salts 6-9 were interpreted as a three-step hierarchical assembly. The para-substituents of the (R)-1-arylethylammonium cations were found on sheet structures consisting of 2(1) columns. Thus, salts possessing smaller para-substituents, that is, salt 7 (p-F) and salt 9 (p-H), and larger para-substituents, that is, salt 6 (p-OMe) and salt 8 (p-Cl), crystallized in the space groups P2(1) and C2, respectively. Additionally, weak intermolecular interactions, that is, aromatic C-H center dot center dot center dot pi, C-H center dot center dot center dot<bold>F</bold>, and C-H center dot center dot center dot<bold>O interactions</bold>, were examined in crystalline salts 6-9.