Scheme 1210

upon oxidation at 1 V, as well as at 1.5 V, the intensity of the positive Cotton effect at 360 nm decreased to 40% of the initial value and that the negative Cotton effect at 250 nm disappeared. The CD signal could be restored by reduction at 0.2 V. The same behavior was observed by chemical oxidation and reduction of the fer-rocenyl groups. Upon oxidation, the helical backbone is believed to be transformed into a disordered structure by the electrostatic repulsion of the ferroce-nium ions.

In the group of Amabilino, polymer 56 containing tetrathiafulvalene (TTF) units has been designed and synthesized with the objective of constructing a chiral redox polymer [114]. The polymer has three univalent and two wide mixed-valence redox states, which are fully interconvertible (Fig. 12.12). The different redox states of the polymer, in contrast to the monomer, exhibited clearly

Kvs s-V

0 0

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