Interactions of the aromatic cavity of rigid calix[4]arene cone conformerswith acid CH3 and CH2 containing guests in apolar solvents

The effect of the acidity of CH groups within the guests on the binding abi lity of the aromatic cavity of rigid cone conformers of p-tert-butylcalix[4 ]arene toward guests containing acid CH3 and CH2 groups have been investiga ted in apolar media by H-1 NMR spectroscopy. In CDCl3 and/or CCl4, CH3Y and CH2XY guests show different binding modes. In particular the acidity of th e CH2XY guests strongly affects the binding efficiency whereas the guest ac idity does not seem the sole parameter in determining the stability of the complexes with CH3Y guests. With methylene containing guests, the polarizab ility of the X and Y groups strongly affect the binding process and the Del taG(0) of complexation is linearly correlated with both pK(a) and polarizab ility of the guests. Solid state structures of sodium and potassium complex es of tetrakisdiethylamide of p-tert-butylcalix[4]arene superset of CH3CN c omplexes are discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.