Gas-Phase Anion Photoelectron Spectroscopy of Alkanethiolate-Protected PtAu Superatoms: Charging Energy in Vacuum vs Solution.

The charging behavior of molecular Au clusters protected by alkanethiolate (SCH=SCn) is, under electrochemical conditions, significantly affected by the penetration of solvents and electrolytes into the SCn layer. In this study, we estimated the charging energy E(n) associated with [PtAu(SCn)]+e→[PtAu(SCn)] (n=4, 8, 12, and 16) in vacuum using mass-selected gas-phase anion photoelectron spectroscopy of [PtAu(SCn)] (z=-1 and -2). The E(n) values of PtAu(SCn) in vacuum are significantly larger than those in solution and decrease with n in contrast to the behavior reported for Au(SCn) in solution.

Electron Affinities of Ligated Icosahedral M Superatoms Revisited by Gas-Phase Anion Photoelectron Spectroscopy.

The electron binding energies of the ligand-protected gold/silver-based cluster anions, [Au(SR)], [XAg(SR')] (X = Ag, Au, Pd, or Pt), and [PdAu(C≡CR″)] having icosahedral M 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.

Electron Binding in a Superatom with a Repulsive Coulomb Barrier: The Case of [Ag(SCHF)] in the Gas Phase.

The electron binding mechanism in [Ag(SCHF)] (SCHF = 3,4-difluorobenzenethiolate) tetra-anion was studied by photoelectron spectroscopy (PES), collision-induced dissociation mass spectrometry (CID-MS), and density functional theory (DFT) computations. PES showed that [Ag(SCHF)] is energetically metastable with respect to electron autodetachment {[Ag(SCHF)] + e} and features a repulsive Coulomb barrier (RCB) with a height of 2.7 eV.