Structure determination of liquid molecules by encapsulation in an aromatic cavity with hydrogen bonding and enhanced C–H⋯π interactions

Abstract

Guanidinium–naphthalenedisulfonic acid (GNPS) was used as a molecular catcher because (i) it contains a cavity and channel in the network; (ii) NH₂⁺ can be used as a hydrogen bond donor, and SO₃⁻ can be used as a hydrogen bond acceptor; (iii) the co-planar naphthalene rings can form aromatic interactions with guest molecules. The liquid guests 1–8 [(−)-isopulegol (1), (−)-menthyl acetate (2), isoeugenol (3), 2,6-dimethylaniline (4), methyleugenol (5), 2,6-diisopropylaniline (6), methyl salicylate (7) and L(−)-carvone (8)] are successfully encapsulated in the cavity of GNPS and eight new crystals were obtained. Both aromatic and non-aromatic molecules form hydrogen bonds and C–H⋯π interactions with GNPS. Co-crystallization of 1–4 with GNPS led to stronger C–H⋯π interactions as compared to the previously reported GBPS. Furthermore, compounds 5–8 which were not co-crystallized with GBPS were found to be encapsulated in the cavity of GNPS. We found that the aromatic cavity of GNPS with hydrogen bonding and enhanced C–H⋯π interactions can be regarded as a useful tool for the structural determination of liquid molecules. Furthermore, the correct absolute configurations of 1, 2 and 8 can be assigned based on the small Flack parameters because of the presence of sulfur atoms in the host molecule GNPS.