Cyclic ion mobility of doped [MAu$_{24}$ L$_{18}$]$^{2-}$ superatoms and their fragments (M = Ni, Pd and Pt; L = alkynyl)

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 [MAu$_{24}$(C-CR)$_{18}$]$^{2-}$, M = Ni, Pd, or Pt, and their associated fragment ions. The three different
alkynyl ligand-stabilized (C-CR, R = 3,5-(CF$_3$)$_2$C$_6$H$_3$), 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 [MAu$_{24}$(C- CR)$_{18}$]$^2$ species fragment by
sequential diyne loss to form [MAu$_{24}$(C- CR)$_{18n}]$$^2$, with n up to 12. The resultant fragment isomer
distributions are significantly n- and M-dependent, and hint at a process involving concerted elimination
of adjacent ligands. In particular [NiAu$_{24} (C-CR)_{18}$]$^2$ also fragments to generate alkyne-oligomers, an
inference supported by the parallel observation of precursor dianion isomerization as collision energy is
increased.