Metal Nitride Cluster Fullerene M3N@C-80 (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 I-h-Sc3N@C-80 and I-h-Y3N@C-80 connected to an electron-donor unit (i.e., tetrathiafulvalene, phthalocyanine or ferrocene) were successfully prepared by 1,3-dipolar cyclo-addition reactions of azomethine ylides and Bingel-Hirsch-type reactions. Electrochemical studies confirmed the formation of the [6,6] regioisomers for the Y3N@C-80-based dyads and the [5,6] re-gioisomers in the case of Sc3N@C-80-based dyads. Similar to other TNT endohedral metallofullerene systems previously synthesized, irreversible reductive behavior was observed for the [6,6]-Y3N@C-80-bascd dyads, whereas the [5,6]-Sc3N@C-80-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, pholophysical investigations on a ferrocenyl-Sc3N@ C-80-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 C-60 dyad.