Group-recognition ability of derivatized beta-cyclodextrin as studied by the ESR spin probing technique

The effect of modifying the entrance face of beta-cyclodextrin on the inclusion of various functional groups in aminoxyl spin probes was determined by the use of heptakis (2,6-O-dimethyl)-beta-cyclodextrin and heptakis (2,3,6-O-triacetyl)-beta-cyclodextrin. The methylation of six of the secondary hydroxyl groups on the wider end of beta-cyclodextrin has a variable effect on the association constant of inclusion depending on the nature of the included group. The role of the methoxy group on the rim is discussed on the basis of the thermodynamic data derived from association constants. Contrary to the unmodified beta-cyclodextrin the pH of the solution does not influence the inclusion behaviour.