(Invited) Novel Dysprosium-Based Metalloazafullerenes: Syntheses, Structures and Properties

Abstract

Substituting a carbon atom on the carbon cage (C2n) by nitrogen can lead to a special kind of fullerene called azafullerene (C2n-1N), which tends to form a dimer due to its paramagnetic property. When an azafullerene monomer, acting as a nanocontainer, encounters metal atoms or clusters, the extra electron generated by the nitrogen substitution would be transferred to the internal metal or cluster center. This may lead to the enhancement of metal-metal interaction, the capture of metastable species and concomitantly some interesting chemical and physical properties.Here, we have synthesized and crystallographically characterized two novel metalloazafullerenes Dy2@C79N and Dy2N4@C81N with quasi-C80-Ih (7) and quasi-C82-C 3v (8) cages, respectively. Owing to the strong exchange coupling between two dysprosium ions via radical bridges, Dy2@C79N behaves as an excellent single-molecule magnet with large energy barrier of U = 669 ± 7 K and observable hysteresis loops below 24 K. Dy2N4@C81N is the first entity of capturing the unstable four-membered nitrogen ring (cyclo-N4) with definitive structure characterized by single-crystal x-ray diffraction (XRD) analysis. The results show that a planar cyclo-N4 coordinated with two dysprosium ions to form a distorted octahedral cluster inside the C81N cage. These works will inspire further exploration of the properties and applications of metalloazafullerenes. Keywords: Metalloazafullerene; Single-molecule magnet; Four-membered nitrogen ring