Inclusion complex formation constants of α-, β-, γ-, δ-, ε-, ζ-, η- and θ-cyclodextrins determined with capillary zone electrophoresis

In contrast to the well known small cyclodextrins (CD), cyclomaltohexaose (α-CD), cyclomaltoheptaose (β-CD) and cyclomaltooctaose (γ-CD), very limited information is available on larger CD and their inclusion complex forming properties. Using capillary electrophoresis, the binding constants of inclusion complexes formed with cyclomaltononaose (δ-CD), cyclomaltodecaose (ε-CD), cyclomaltoundecaose (ζ-CD), cyclomaltododecaose (η-CD) and cyclomaltotridecaose (θ-CD) and various anions were determined and compared to the corresponding binding constants of α-, β- and γ-CD. All of the large CD were capable to form inclusion complexes. Dependent on the type of guest molecules, δ- and ε-CD were the weakest complex formers. The complex forming ability of ε, ζ-, η-, and θ-CD increased with increasing size of the ring structure and θ-CD displayed inclusion complex formation constants comparable to γ-CD.