Electron Affinities of Ligated Icosahedral M(13) Superatoms Revisited by Gas-Phase Anion Photoelectron Spectroscopy

[Image: see text] The electron binding energies of the ligand-protected gold/silver-based cluster anions, [Au(25)(SR)(18)](−), [XAg(24)(SR′)(18)](2–) (X = Ag(+), Au(+), Pd(0), or Pt(0)), and [PdAu(24)(C≡CR″)(18)](2–) having icosahedral M(13) superatomic cores, were reexamined by gas-phase photoelectron spectroscopy (PES) on a significantly intensified mass-selected ion beam. Laser fluence-dependent PE spectra and pump–probe PES revealed that the previous PE spectra were contaminated by PE signals due to the two-photon electron detachment via long-lived photoexcited states. Although the adiabatic electron affinities (AEAs) of the corresponding oxidized forms were found to be 1–2 eV larger than those previously reported, the effects of doping and ligation were not qualitatively affected. (1) The AEA of the Ag(13) superatom (∼4 eV) was not appreciably affected by doping a Au atom at the center but was reduced by ∼2 eV by doping Pd or Pt, and (2) the AEA of PdAu(12) protected by Au(2)(C≡CR″)(3) units was much larger than that of PdAg(12) protected by Ag(2)(SR′)(3) units.