1H NMR titration and quantum calculation for the inclusion complexes of cis-cyclooctene, cis, cis-1, 3-cyclooctadiene and cis, cis-1, 5-cyclooctadiene with β-cyclodextrin

The inclusion behavior of cis-cyclooctene, cis, cis-1, 3-cyclooctadiene and cis, cis-1, 5-cyclooctadiene with β-cyclodextrin (β-CD) was studied by using 1H NMR method in D2O/CD3OD solution and PM3 quantum-chemical simulation in vacuum. The experimental results indicate that each guest molecule penetrates deeply into β-CD cavity and forms equimolecular inclusion complex with the host. The association constants of the complexes were determined by non-linear least-square method on the bases of the conversion-dependent chemical shift of two protons of the host molecule. The inclusion process and the most probable structure of the inclusion complexes were simulated using PM3 energy scanning and optimization. The trend of stability of the three inclusion complexes deduced from their calculated stabilization energies agrees well with the order of their association constants obtained from NMR experiments.