Redox-Mediated Reversible σ-Bond Formation/Cleavage

The redox-induced change in the bond order occurs not only in the π-conjugated systems but in the system where the σ-bond formation/cleavage is accompanied by electron transfer. Due to the dynamic geometrical changes upon redox reactions, the chromism based on the dyrex systems could be accompanied by more advanced features. Irrespective of the "π/ σ"- or "exo/endo"-type classification, the characteristic features of a dyrex system are facile 2e-transfer nearly at the same potentials and the electrochemical bistability, which are in sharp contrast to those of a conventional redox system. When the two dyrex units are connected with a proper spacer, the resulting dyad would exhibit a unique redox scheme, which is far different from the dyads consisting of conventional redox units. Since the dyrex unit could be potentially used as a "unimolecular molecular memory", the molecule with multiple dyrex units would be developed toward "molecular n-bit memory".