Synthesis and Characterization of a Novel Non-Isolated-Pentagon-Rule Isomer of Th@C76:Th@C1(17418)-C76

A novel Non-Isolated-Pentagon-Rule (non-IPR) isomer of thorium-based endohedral mono-metallofullerenes (mono-EMFs), Th@C1(17418)-C76, was successfully synthesized and characterized using MALDI-TOF mass spectroscopy, single-crystal X-ray diffraction, UV-vis-NIR spectroscopy, and Raman spectroscopy. The molecular structure of this non-IPR isomer was determined unambiguously as Th@C1(17418)-C76 using a single-crystal X-ray diffraction analysis. The crystallographic results further revealed that the optimal Th site resided at the intersection of two adjacent pentagons, similar to that of U@C1(17418)-C76. Additionally, the UV-vis-NIR spectra of Th@C1(17418)-C76 exhibited distinct differences compared to the previously reported U@C1(17418)-C76, highlighting the distinctive electronic structure of actinium-based endohedral metallofullerenes (EMFs). The Raman spectrum of Th@C1(17418)-C76 exhibited similarities to that previously reported for thorium-based EMFs, indicating the analogous strong metal–cage interactions of thorium-based EMFs.