Variable temperature CP/MAS13C NMR study of cyclodextrin complexes of benzaldehyde

Abstract

Fully hydrated as well as dried benzaldehyde complexes of α- and β-cyclodextrins were studied by using CP/MAS13C NMR techniques. Variable temperature studies have shown that below ∼ 200 K the guest is rigidly held in the complex, whereas at 328 K, only the aromatic ring performs rapid two-fold flips about the C1-C4 axis. In the β-Cd complex the benzaldehyde performs more general reorientation. Removal of water causes marked changes in both guest and host spectra, generally consistent with a loss of short-range order and increase in guest motional rate. © 1988 National Research Council of Canada.