Redox-responsive self-assembly of β-cyclodextrin and ferrocene double-headed amphiphilic molecules

We present a redox-responsive self-assembly based on a unimolecular platform. Three double-headed amphiphilic molecules composed of beta-cyclodextrin (beta-CD) and ferrocene (Fc) each with an alkyl chain as a linker (beta CD-C-m-Fc, m = 2, 6, and 10) were synthesized, and their self-assembly behaviors were investigated. The molecules self-assembled into polydisperse micelles that transformed into vesicles upon oxidization of the Fc moieties to Fc(+). 2D H-1 NMR results suggest that although the three molecules formed aggregates with similar morphologies, their molecular configurations were different because of the different lengths of the alkyl chains. When the linker was a C-2 chain, no host-guest complexes were formed, whereas host-guest recognition was detected for linker lengths of C-6 and C-10. For the oxidized state samples, there were no host-guest interactions for linker lengths of C-2 and C-6, whereas the alkyl chain was locked in the cavity of beta-CD by host-guest inclusion for the molecule with a C-10 linker. Moreover, reversible redox-responsive self-assemblies based on the three beta-CD derivatives with a terminal Fc were successfully achieved. Our results enrich the field of beta-CD/Fc reversible self-assembly systems, and provide a possible unimolecular host-guest complexation model in host-guest chemistry.