Metal Nitride Cluster Fullerene M3N@C80 (M=Y, Sc) Based Dyads: Synthesis, and Electrochemical, Theoretical and Photophysical Studies

The first pyrrolidine and cyclopropane derivatives of the trimetallic nitride templated (TNT) endohedral metallofullerenes Ih‐Sc3N@C80 and Ih‐Y3N@C80 connected to an electron‐donor unit (i.e., tetrathiafulvalene, phthalocyanine or ferrocene) were successfully prepared by 1,3‐dipolar cycloaddition reactions of azomethine ylides and Bingel–Hirsch‐type reactions. Electrochemical studies confirmed the formation of the [6,6] regioisomers for the Y3N@C80‐based dyads and the [5,6] regioisomers in the case of Sc3N@C80‐based dyads. Similar to other TNT endohedral metallofullerene systems previously synthesized, irreversible reductive behavior was observed for the [6,6]‐Y3N@C80‐based dyads, whereas the [5,6]‐Sc3N@C80‐based dyads exhibited reversible reductive electrochemistry. Density functional calculations were also carried out on these dyads confirming the importance of these structures as electron transfer model systems. Furthermore, photophysical investigations on a ferrocenyl–Sc3N@C80‐fulleropyrrolidine dyad demonstrated the existence of a photoinduced electron‐transfer process that yields a radical ion pair with a lifetime three times longer than that obtained for the analogous C60 dyad. Endohedral fullerene dyads: The reactivity of Ih‐Sc3N@C80 and Ih‐Y3N@C80 (see figure) towards 1,3‐dipolar azomethine ylide and Bingel–Hirsch cycloaddition reactions was explored in order to construct different electron donor–acceptor conjugates. The unique redox properties of the structures formed were investigated by means of cyclic voltammetry and the experimental results were supported by density functional calculations.