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

Abstract

The first pyrrolidine and cyclopropane derivatives of the trimetallic nitride templated (TNT) endohedral metallofullerenes I(h)-Sc(3)N@C(80) and I(h)-Y(3)N@C(80) 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 Y(3)N@C(80)-based dyads and the [5,6] regioisomers in the case of Sc(3)N@C(80)-based dyads. Similar to other TNT endohedral metallofullerene systems previously synthesized, irreversible reductive behavior was observed for the [6,6]-Y(3)N@C(80)-based dyads, whereas the [5,6]-Sc(3)N@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, photophysical investigations on a ferrocenyl-Sc(3)N@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.

Chemical, Electrochemical, and Structural Properties of Endohedral Metallofullerenes

“…[73] Two Bingel adducts of Y 3 N@C 80 with anthraquinone and Pc moieties were synthesized and characterized by Echegoyen and co-workers. [65] …”

“…Therefore, the band gap can be finely tuned, which is a clear asset for potential applications in molecular electronics. On the other hand, the relative inertness of the carbon cage could lead to medical applications for some exTTF-CHO [65] 0.06 AQ-CH 2 OH [65] À1.50 À1.84 Fc-CHO [65] 0.20…”

“…[64] Finally, Echegoyen and co-workers reported new pyrrolidine derivatives of metallic nitride EMFs with different dyad substituents (phthalocyanine (Pc), and ferrocene) attached to the pyrrolidine ring. [65] A [5,6] adduct was obtained for Sc 3 N@C 80 (I h ) and a [6,6] adduct was obtained for Y 3 N@C 80 (I h ). [65] …”

“…[65] A [5,6] adduct was obtained for Sc 3 N@C 80 (I h ) and a [6,6] adduct was obtained for Y 3 N@C 80 (I h ). [65] …”

“…[21,65] The chosen electron donors were extended tetrathialfulvalene (exTTF) and ferrocene (Fc). The exTTF adduct of Y 3 N@C 80 was very unstable and was rapidly oxidized to an anthraquinone (AQ) adduct.…”