Direct versus indirect electron transfers in host-guest-inclusion complexes: Example of the oxidation of TTF-β-CD complexes
Résumé
The possibility of homogeneous electron transfers besides the heterogeneous transfers into host-guest electroactive systems have been examined in details with the case of a simple system: the TTF oxidation in water in presence of a cyclodextrin. The global mechanism can be described by a classical CE mechanism taking into account the existence of fast homogeneous electron transfers. It appears that the guest-host complex between the TTF and the cyclodextrin is efficiently oxidised in solution through a homogeneous pathway without prior to dissociation, the dication playing a role of catalyst able to access in the cavity. Contrarily to the generally reported behaviour for host-guest complexes, the direct electron transfer to the guest molecule is also possible even if its kinetics is relatively slow (ks,app in the 10−3 cm s−1 range).