Studies of Naphthyl-Substituted β-Cyclodextrins. Self-Aggregation and Inclusion of External Guests

Studies of 3- O -(2-methylnaphthyl)-β-cyclodextrin ( 1 ) with various spectroscopic methods including 1 H NMR, fluorescence, UV−vis, and circular dichroism yield information on the character of this compound. NOESY data indicate the naphthyl moiety binds inside the cyclodextrin cavity. 1 H NMR concentration-dependent studies reveal that 1 is a dimer at concentrations of >10 - 4 M. The circular dichroism spectrum of dilute samples is consistent with a monomer. Analysis of 1 complexing with 2-( p -toluidino)-6-naphthalenesulfonate (TNS) with both fluorescence and 1 H NMR demonstrates that a hydrophobic interaction occurs between 1 and TNS. The concentration dependence of this interaction is strongly affected by the dimerization equilibrium of 1 .