1H and 13C NMR Studies of Formation and Molecular Dynamics of Methylated-Cyclodextrin Inclusion Complexes with Phenylalanine

The formation and the molecular dynamics of the host-guest inclusion complexes in aqueous solution have been studied for hosts α- and permethylated α-cyclodextrin and permethylated β-cyclodextrin and guest phenylalanine by 1H and 13C NMR spectroscopy. The changes in 1H chemical shift, 1H spin-coupling constant, and 13C spin-lattice relaxation time for the guest phenylalanine on addition of the host cyclodextrin show that they form the inclusion complexes in a similar manner, that is, by insertion of the guest’s phenyl ring into the host’s cavity. The strength of the host–guest dynamic coupling varies with the cavity size of cyclodextrins.