Molecular engineering. Part 9: Enhanced binding ability and selectivity of C2v cavitands

Two new C2v cavitands with protective side chains were synthesized and their binding properties for small molecules were studied. Cavitand 7 having benzyl side chains binds ethanol most strongly with Ka = 1508 M−1 at 20 °C in CDCl3, which was driven entropically. Cavitand 8 having coumarinyl side chains showed weaker binding due to its steric hindrance. 1H NMR spectra show that carceroisomers of ethanol or acetonitrile@cavitand 7 exist in 3:1 ratio at 20 °C. The binding tendencies of the guest molecules were increased in nonpolar solvent media.