Gas phase ion chemistry of titanium–oxofullerene with ligated solvents

Abstract

We investigated the gas phase fragmentation events of highly symmetric fullerene-like (FN-like) titanium oxo-cluster anions, [H₁₂Ti₄₂O₆₀(OCH₃)₄₂(HOCH₃)₁₀(H₂O)₂]²⁻ (1) and [H₇Ti₄₂O₆₀(OCH₃)₄₂(HOCH₃)₁₀(H₂O)₃]¹⁻ (2). These oxo-clusters contain a closed cage Ti₄₂O₆₀ core, protected by a specific number of methoxy, methanol, and water molecules acting as ligands. These dianionic and monoanionic species were generated in the gas phase by electrospray ionization of the H₆[Ti₄₂(μ³-O)₆₀(OⁱPr)₄₂(OH)₁₂] (TOF) cluster in methanol. Collision induced dissociation studies of 1 revealed that upon increasing the collision energy, the protecting ligands were stripped off first, and [Ti₄₁O₅₈]²⁻ was formed as the first fragment from the Ti₄₂O₆₀ core. Thereafter, systematic TiO₂ losses were observed giving rise to subsequent fragments like [Ti₄₀O₅₆]²⁻, [Ti₃₉O₅₄]²⁻, [Ti₃₈O₅₂]²⁻, etc. Similar fragments were also observed for monoanionic species 2 as well. Systematic 23 TiO₂ losses were observed, which were followed by complete shattering of the cage. We also carried out computational studies using density functional theory (DFT) to investigate the structures and fragmentation mechanism. The fragmentation of TOF was comparable to the fragmentation of C₆₀ ions, where systematic C₂ losses were observed. We believe that this is a consequence of topological similarity. The present study provides valuable insights into the structural constitution of TOF clusters and stability of the parent as well as the resulting cage-fragments in the gas phase.