COMPLEXATION OF AMINO-ACIDS BY CYCLOTETRACHROMOTROPYLENE IN AQUEOUS-SOLUTION - IMPORTANCE OF CH-PI AND PI-PI INTERACTIONS

The stability constants K of the 1:1 host to guest complexes formed be tween the cyclic tetramer, cyclotetrachromotropylene, and amino acids in water at pD 7.0 and 25 degrees C were determined by H-1 nmr spectro scopy. The results indicate that the interactions between the aromatic pi-bonds of the host and the C-H bonds (for aliphatic amino acids) an d aromatic pi-bonds (for aromatic amino acids) of the guests are the m ajor factors responsible for the complexation. There is a linear relat ionship between log K and the number of C-H bonds interacting with the hydrophobic host cavity.