The members of a new family of yttrium trimetallic nitride-templated (TNT) endohedral metallofullerenes (EMFs), Y3N@C-2n (n = 40-43), have been synthesized and purified. On the basis of experimental and computational C-13 NMR studies, we propose cage structures for Y3N@I-h-C-80 (IPR allowed), Y3N@D-5h-C-80 (IPR allowed), Y3N@C-s-C-82 (non-IPR), Y3N@C-s-C-84 (non-IPR), and Y3N@D-3-C-86 (IPR allowed). A significant result is the limited number of isomers found for each carbon cage. For example, there are 24 isolated pentagon rule (IPR) and 51 568 non-IPR structures possible for the C-84 cage, but only one major isomer of Y3N@C-s-C-84 was found. The current study confirms the unique role of the trimetallic nitride (M3N)(6+) cluster template in the Kratschmer-Huffman electric-arc process for fullerene cage size and high symmetry isomer selectivity. This study reports the first Y-89 NMR results for Y3N@I-h-C-80, Y3N@C-s(51365)-C-84, and Y3N@D-3(19)-C-86, which reveal a progression from isotropic to restricted (Y3N)(6+) cluster motional processes. Even more surprising is the sensitivity of the Y-89 NMR chemical shift parameter to subtle changes in the electronic environment at each yttrium nuclide in the (Y3N)(6+) cluster (more than 200 ppm for these EMFs). This Y-89 NMR study suggests that Y-89 NMR will evolve as a powerful tool for cluster motional studies of EMFs.