1 : 1 and 1 : 2 complexation thermodynamics of gamma-cyclodextrin with N-carbobenzyloxy aromatic amino acids and omega-phenylalkanoic acids

The stability constants (K), standard free energies (DeltaG degrees), entha lpies (DeltaH degrees), and entropy changes (T DeltaS degrees) for the comp lexation of gamma -cyclodextrin with N-carbobenzyloxy (CBZ)-D/L-phenylalani ne, CBZ-D/L-tyrosine, CBZ-D/L-tryptophan, CBZ-D/L-histidine, CBZ-glycine, 3 -phenylpropionic acid, 4-phenylbutyric acid, 5-phenylvaleric acid, and 6-ph enylhexanoic acid have been determined in phosphate buffer solution (pH 6.9 ) at 298.15 K by titration microcalorimetry, The trends observed in the the rmodynamic parameters for 1:1 and/or 2:1 host-guest complexation correlate with the systematic structural changes of the guest molecules. On the basis of the results obtained, we further discuss the possible thermodynamic imp lication for the entropic control of supramolecular systems.