Elucidating the Doping Effect on the Electronic Structure of Thiolate‐Protected Silver Superatoms by Photoelectron Spectroscopy

• Published in: Angewandte Chemie International Edition 2019-08, Vol.58 (34), p.11637-11641
• Main Authors: Kim, Kuenhee, Hirata, Keisuke, Nakamura, Katsunosuke, Kitazawa, Hirokazu, Hayashi, Shun, Koyasu, Kiichirou, Tsukuda, Tatsuya
• Format: Article
• Language: English
• Subjects: Anion photoelectron spectroscopy; Doping; doping effects; Electronic structure; Electrons; Gold; Icosahedral phase; multiply charged anions; Orbitals; Organic chemistry; Palladium; Photoelectron spectroscopy; Photoelectrons; Platinum; repulsive Coulomb barrier; Silver; Spectroscopy; Spectrum analysis; thiolate-protected silver cluster; Vacuum
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201901750

Gas‐phase photoelectron spectroscopy (PES) was conducted on [XAg24(SPhMe2)18]− (X=Ag, Au) and [YAg24(SPhMe2)18]2− (Y=Pd, Pt), which have a formal superatomic core (X@Ag12)5+ or (Y@Ag12)4+ with icosahedral symmetry. PES results show that superatomic orbitals in the (Au@Ag12)5+ core remain unshifted with respect to those in the (Ag@Ag12)5+ core, whereas the orbitals in the (Y@Ag12)4+ (Y = Pd, Pt) core shift up in energy by about 1.4 eV. The remarkable doping effect of a single Y atom (Y=Pd, Pt) on the electronic structure of the chemically modified (Ag@Ag12)5+ superatom was reproduced by theoretical calculations on simplified model systems and was ascribed to 1) the weaker binding of valence electrons in Y@(Ag+)12 compared to Ag+@(Ag+)12 due to the reduction in formal charge of the core potential, and 2) the upward shift of the apparent vacuum level due to the presence of a repulsive Coulomb barrier between [YAg24(SPhMe2)18]− and electron. Central exchange: The heteroatom doping effect on superatomic orbitals in [XAg24(SR)18]− (X=Ag, Au) and [YAg24(SR)18]2− (Y=Pd, Pt) was examined using gas‐phase photoelectron spectroscopy. The adiabatic electron affinity of [XAg24(SR)18] is reduced by approximately 1.4 eV upon replacement of the central X+ cation by a neutral Y atom.