Molecular interactions of -cyclodextrins with monolayers containing adamantane and anthraquinone guest groups

Complexing abilities of -cyclodextrin (-CD) towards anthraquinone derivatives in solution and immobilised on gold surfaces were studied by voltammetry. The association constant of -CD with 1-aminoanthraquinone in solution was found to be 1.03 +/- 0.05x103M-1; hence, smaller than that with anthraquinone. Capping the surface-immobilised N-(1-anthraquinone) lipoamide with -CD led to decrease in the heterogeneous electron transfer rate constant due to the change in the immediate environment around the electroactive group. To detect the interactions of -CD with a non-electroactive guest, N-(1-adamantane) lipoamide (AD-Lip), the CD was modified by the attachment of an anthraquinone group as the electroactive marker. The appearance of the voltammetric peak corresponding to the reduction of the anthraquinone side-group indicated the binding of -CD to the AD-Lip self-assembled in a monolayer on the gold electrode.