Electronic Properties and ¹³C NMR Structural Study of Y₃N@C₈₈

In this paper, we report the synthesis, purification, ¹³C NMR, and other characterization studies of Y₃N@C₈₈. The ¹³C NMR, UV−vis, and chromatographic data suggest an Y₃N@C₈₈ having an IPR-allowed cage with D₂(35)-C₈₈ symmetry. In earlier density functional theory (DFT) computational and X-ray crystallographic studies, it was reported that lanthanide (A₃N)⁶⁺ clusters are stabilized in D₂(35)-C₈₈ symmetry cages and have reduced HOMO−LUMO gaps relative to other trimetallic nitride endohedral metallofullerene cage systems, for example, A₃N@C₈₀. In this paper, we report that the nonlanthanide (Y₃N)⁶⁺ cluster in the D₂(35)-C₈₈ cage exhibits a HOMO−LUMO gap consistent with other lanthanide A₃N@C₈₈ molecules based on electrochemical measurements and DFT computational studies. These results suggest that the reduced HOMO−LUMO gap of A₃N@C₈₈ systems is a property dominated by the D₂(35)-C₈₈ carbon cage and not f-orbital lanthanide electronic metal cluster (A₃N)⁶⁺ orbital participation.