Articles Molecular Recognition of Neutral Substrates by New Tetraaminocalix[4]arene Derivative

The recognition of neutral aromatic substrates by different neutral calix[4]arene receptors 1, 2, and 3 was studied by NMR spectroscopy. The stoichiometry is 1:1 in all cases as was confirmed by jobs plot. Owing to the deep cavity, 1 affords stronger binding abilities for substrate 4 and 5, while all receptors remained inert for substrates 6 and 7. The binding constants determined by 1H NMR titration show that the recognition of substrate 4 by 1 gives strongest complexation (Ka of 9.8 × 102 M-1)