Interfacial supramolecular cyclodextrin-fullerene assemblies: host reorientation and guest stabilization

Monolayers of mono and bis-pyridine-substituted beta- and gamma-cyclodextrins have been self-assembled onto polycrystalline gold electrodes and electrochemically characterised. Surface enhanced Raman spectroscopy (SERS) has been used to probe the time dependent reorientation of the CDs and to probe the effect of co-adsorbing alkane thiols. Significantly, we observe novel SERS signatures for carbohydrate centred between 2100 and 2300 cm(-1) which is sensitive to the orientation of the CD moiety on the gold surface. These modes are thought to arise from direct interactions between the CD pyranose ring and the gold substrate and are useful markers for assigning orientation of CD within a film. SERS confirmed, as was intimated from a previous electrochemical study, that significant reorientation of the CD groups within the film occurs on annealing and this orientation can be reversed by backfilling with alkane thiol. C-60, in its unmodified state, was then immobilised through host-guest assembly into the backfilled CD monolayers to produce a 2 : 1 CD: C60 trilayer. These CD capped fullerenes are protected from photopolymerisation and exhibit well-defined redox processes.