Electronic Properties and <sup>13</sup>C NMR Structural Study of Y<sub>3</sub>N@C<sub>88</sub>

In this paper, we report the synthesis, purification, <sup>13</sup>C NMR, and other characterization studies of Y<sub>3</sub>N@C<sub>88</sub>. The <sup>13</sup>C NMR, UV−vis, and chromatographic data suggest an Y<sub>3</sub>N@C<sub>88</sub> having an IPR-allowed cage with <i>D</i><sub>2</sub>(35)-C<sub>88</sub> symmetry. In earlier density functional theory (DFT) computational and X-ray crystallographic studies, it was reported that lanthanide (A<sub>3</sub>N)<sup>6+</sup> clusters are stabilized in <i>D</i><sub>2</sub>(35)-C<sub>88</sub> symmetry cages and have reduced HOMO−LUMO gaps relative to other trimetallic nitride endohedral metallofullerene cage systems, for example, A<sub>3</sub>N@C<sub>80</sub>. In this paper, we report that the nonlanthanide (Y<sub>3</sub>N)<sup>6+</sup> cluster in the <i>D</i><sub>2</sub>(35)-C<sub>88</sub> cage exhibits a HOMO−LUMO gap consistent with other lanthanide A<sub>3</sub>N@C<sub>88</sub> molecules based on electrochemical measurements and DFT computational studies. These results suggest that the reduced HOMO−LUMO gap of A<sub>3</sub>N@C<sub>88</sub> systems is a property dominated by the <i>D</i><sub>2</sub>(35)-C<sub>88</sub> carbon cage and not f-orbital lanthanide electronic metal cluster (A<sub>3</sub>N)<sup>6+</sup> orbital participation.