Redox Switching of Anthracene Fluorescence through the CuII/CuI Couple

The bistable system [CuI,II(2)]+/2+ was prepared, which indeed behaved as an efficient fluorescence switch. However, switching was not matter of electronic configuration, but of redox potential. In the OFF situation, the *AncT excited state is able to transfer an electron to the Cu" center, in view (i) of the relatively high value of the Cu"/Cu' redox couple potential (a property provided by the S4 environment) and (ii) of the tendency on anthracene to be oxidized. On the other hand, (i) the CuI state is poorly reducing and, in particular, (ii) anthracene is especially resistent to the reduction, which does not induce any electron transfer process, maintains fluorescence and generates the ON situation.