Ti2S@D3h(24109)-C78: a sulfide cluster metallofullerene containing only transition metals inside the cage

A new titanium-based sulfide clusterfullerene, Ti2S@D-3h(24109)-C-78, has been successfully synthesized by arc-discharging graphite rods packed with pure TiO2 and graphite powder under an atmosphere of SO2 and helium. Multistage HPLC methods were utilized to isolate and purify the Ti2S@C-78, and mass spectrometric characterization confirmed the composition of a Ti2S cluster within a C-78 cage. UV-Vis-NIR absorption spectroscopy, electrochemical characterization and extensive DFT calculations led to the assignment of the cage symmetry to D-3h(24109)-C-78 and suggested an almost linear arrangement of the internal Ti2S cluster, with a formal transfer of six electrons from the cluster to the C-78 cage.