Encapsulation of Iridium with Lanthanum in Fullerenes: Electronegativity Is the Key

The encapsulation of transition metals within fullerenes to form corresponding endohedral metallofullerenes (EMFs) has been a long-standing issue. Here, using laser ablation mass spectrometry, we confirmed that the transition metal Ir could be encapsulated within fullerenes with La atoms to form EMFs of La₃Ir @ C_2n (2n = 98-130). Theoretical calculations performed on La₃Ir @ C₉₈ indicate that its bonding properties are remarkably similar to those of La₃Pt @ C₉₈. This similarity can be attributed to the comparable electronegativity values of iridium and platinum. We predict that other transition metals with appropriate electronegativity values can likewise act as mediators to form encapsulated mixed-metal fullerenes. This work provides valuable guidance and reference for the discovery and synthesis of new transition-metal-containing EMFs.