A systematic study on the generation of multimetallic lanthanide fullerene ions by laser ablation mass spectrometry

Laser ablation masss spectromety has been previously proved to be a powerful tool for studying endohedro metallofullerene (EMF) ions. Our previous study showed the possiblity of forming multi-metallofullerene ions containg more than six metal atoms for La, Y and Lu. Thus, it is important to conduct a systematic study on the generation of multi-metallofullerenes and their distribuitons for all lanthanide elements.

Experiments were performed on a 7.0 T Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Laser ablation mass spectra were obtained by laser irradiation on mixtures of graphene and MCl₃ on a stainless steel plate, applying a 355 nm Nd:YAG laser with a typical energy of 2.5 mJ/pulse. Reaction test experiments were performed by introducing O₂ into the FTICR cell with a pulse valve.

Multi-metallofullerene ions Ce2-4C2m+, Pr2-4C2m+, Gd2-4C2m+, Nd3C2m+, Dy2-3C2m+, Tb2-7C2m+, Ho2-6C2m+ were observed in the mass spectra. For the metals Sm and Eu, no multi-metallofullerene ion was observed. No reaction with O₂ was observed in the reaction experiments, verifying that these species had endohedral structures. For the observed series of multi-metallofullerene ions, tri-metallofullerene ions dominated their mass spectra. The results were further compared with previously generated EMF ions for La, Er, Tm, Yb and Lu.

Endohedral lanthanide metallofullerene ions were generated by laser ablation of graphene and the corresponding metal salts MCl₃ (M = Ce, Pr, Nd, Gd, Tb, Dy and Ho) and studied with a FTICR mass spectrometer. Typically, multi-metallofullerene ions of TbnC2m+2≤n≤780≤2m≤176 and Ho6C2m+2≤n≤674≤2m≤162 were observed. The results show that the formation of multi-EMF ions containing lanthanides that have +3 and + 4 oxidation states is easier than those containing +2 oxidation states in the process of laser ablation.