Direct versus indirect electron transfers in host–guest-inclusion complexes: Example of the oxidation of TTF–β-CD complexes

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).