An expanded family of dysprosium-scandium mixed-metal nitride clusterfullerenes: the role of the lanthanide metal on the carbon cage size distribution

Abstract

A large family of dysprosium-scandium (Dy-Sc) mixed-metal nitride clusterfullerenes (MMNCFs), Dy(x)Sc(3-x)N@C2n (x = 1, 2, 2n = 68, 70, 76-86) have been successfully synthesized and isolated. Among these, the C70 and C82-based MMNCFs are two new cages that have never been isolated for MMNCFs. Synthesis of Dy(x)Sc(3-x)N@C2n was accomplished by the "selective organic solid" route using guanidinium thiocyanate as the nitrogen source, and their isolation was fulfilled by recycling HPLC. UV/Vis-NIR spectroscopic study indicates that almost all Dy(x)Sc(3-x)N@C2n MMNCFs are kinetically stable fullerenes with optical band gaps beyond 1 eV. This feature is distinctly different to their counterparts Dy3N@C2n (78≤2n≤88), whose for optical band-gaps are below 1 eV for relatively large cages such as C84 and C86. An FTIR spectroscopic study in combination with DFT calculations enables reasonable assignments of the cage isomeric structures of all isolated Dy(x)Sc(3-x)N@C2n (x = 1, 2, 2n = 68, 70, 76-86) MMNCFs. The carbon cage size distribution of Dy(x)Sc(3-x)N@C2n (2n = 68, 70, 76-86) is compared to the reported Dy3N@C2n (78≤2n≤8) homogeneous NCF and Dy(x)Sc(3-x)N@C2n (78≤2n≤88) MMNCF families, revealing that the medium-sized Dy metal plays a crucial role on the expanded cage size distribution of MMNCFs. As a result, Dy(x)Sc(3-x)N@C2n MMNCFs are the largest MMNCF family reported to date.

Keywords: clusterfullerenes; dysprosium; endohedral fullerenes; metal nitrides; scandium.