Influence of the ammonium cation and 18-crown-6 guest on the supramolecular networks of 1,3,5-cyclohexanetricarboxylic acid

Abstract

The title acid 1,3-cis,5-cis-cyclohexanetricarboxylic acid (H 3CTA) forms a three-dimensional anionic host framework via O-H⋯O- hydrogen bonds with 11.2 x 12.7 Å square channels for the inclusion of 18-crown-6 (18-C-6) and NH4+ cation in a Russian doll assembled guest∩cavitand⊂clathrand crystal structure, H2CTA-·H2O·NH4+·18-C-6 (1). Differences in the binding of the ammonium cation to the crown ether and OHNH3+ cation result in a two-dimensional network of H2CTA- anions in H 2CTA-·OHNH3+·18-C-6 (2) that resemble the black phosphorus topology. In contrast to ionic structures 1 and 2, crystal structure of the neutral complex H3CTA·(18- C-6)0.5 (3) is sustained by a size/shape fit of the crown macrocycle in the 14.5 x 14.5 Å hexagonal cavity of the triacid host and 12 C-H⋯O interactions. © 2006 American Chemical Society.