Electrochemically induced dynamics of a benzylic amide [2]catenane

The electrochemistry of a benzylic amide [2]catenane was investigated and c ompared to that of its topologically trivial components. The redox behavior of both the catenane and the uninterlocked macrocycle can be largely under stood in terms of the electrochemistry of smaller molecular fragments and s imple molecular orbital considerations that show that the electroactivity o f the C=O groups is split into two sets of quasi-degenerate potentials sepa rated by a substantial gap. A fast intermolecular reaction follows the redu ction of the macrocycle and smaller fragments, consistent with the correspo nding dimers containing a new C-C bond linking two reduced carbonyls. The c yclic voltammetric behavior of the catenane differs significantly from that of the macrocycle-a feature that must therefore be directly attributable t o the mechanically interlocked molecular architecture of the catenane. In p articular, an intramolecular reaction (irreversible in the CV time scale) o ccurs in the catenane, which is shown to be a function of temperature and s can rate. Simulation of the cyclic voltammograms shows that the intramolecu lar reaction occurs on a time scale wider than that of circumrotation of th e two rings in the neutral molecule, thus excluding that cyclic voltammetry (CV) is monitoring the latter process, Both the analysis of the electroche mical data and semiempirical quantum chemical (MNDO) calculations would sug gest that the electrochemically induced reaction in the catenane is the sol dering of the two interlocked macrocycles: the formation of a C-C bond betw een two reduced carbonyl groups would thus prevent further rotation of the two interlocked rings.