Inclusion complexation of a deep cavitand with imidazoquinoxaline flaps forming stable vase-like conformation

Abstract

The stability of the vase-like conformation of a deep cavitand 1 with four imidazoquinoxaline flaps was studied in CDCl3/CD3OD by 1H NMR method. The annular tautomerism of cavitand 1·4MeOD in CDCl3/CD3OD (1:9 v/v) was investigated by 1H NMR and the free energy of activation (ΔG‡268) of this process was measured as 12.9 kcal/mol at a coalescence temperature of 263 K. The inclusion complexation of 1 with various rod-like fatty amides and fatty esters resulted the formation of host-guest complexes in 1:1 stoichiometry where the alkyl chain of guests are coiled within the cavity and stabilized by CH/π interactions with the enlarged aromatic π surfaces of imidazoquinoxaline flaps.