Cyclic ion mobility of doped [MAu24L18]2− superatoms and their fragments (M = Ni, Pd and Pt; L = alkynyl)

Abstract

Collision-induced dissociation and high-resolution cyclic ion mobility mass spectrometry, along with quantum chemical calculations and trajectory simulations, were used to compare the structures of isolated [MAu₂₄(CCR)₁₈]²⁻, M = Ni, Pd, or Pt, and their associated fragment ions. The three different alkynyl ligand-stabilized (CCR, R = 3,5-(CF₃)₂C₆H₃), transition metal-doped, gold cluster dianions showed mutually resolvable collision cross sections (CCS), which were ordered consistently with their molecular structures from X-ray crystallography. All three [MAu₂₄(CCR)₁₈]²⁻ species fragment by sequential diyne loss to form [MAu₂₄(CCR)_18−n]²⁻, with n up to 12. The resultant fragment isomer distributions are significantly n- and M-dependent, and hint at a process involving concerted elimination of adjacent ligands. In particular [NiAu₂₄(CCR)₁₈]²⁻ also fragments to generate alkyne-oligomers, an inference supported by the parallel observation of precursor dianion isomerization as collision energy is increased.