NMR studies of complex formation between natural cyclodextrins and benzene

Inclusion complexes of benzene (Bz) with cyclodextrins (CD) have been investigated so far using non-NMR techniques resulting in conflicting data. Here, the first application of NMR spectroscopy in combination with rigorous statistical analysis of the results has allowed us to determine accurately the stoichiometry of complexes and their association constants. Titration measurements have been performed by 1 H NMR spectroscopy in D 2 O at a magnetic field B 0 of 14.1 T. αCD and γCD host molecules form weak 1 : 1 complexes with Bz. In contrast, Bz and βCD build 1 : 1 and 2 : 1 complexes coexisting in solution with large binding constants. Binding of second benzene molecule is strongly cooperative.