title: A unified view of ligand-protected gold clusters as superatom complexes.
abstract: Synthesis, characterization, and functionalization of self-assembled, ligand-stabilized gold nanoparticles are long-standing issues in the chemistry of nanomaterials. Factors driving the thermodynamic stability of well documented discrete sizes are largely unknown. Herein, we provide a unified view of principles that underlie the stability of particles protected by thiolate (SR) or phosphine and halide (PR(3), X) ligands. The picture has emerged from analysis of large-scale density functional theory calculations of structurally characterized compounds, namely Au(102)(SR)(44), Au(39)(PR(3))(14)X(6)(-), Au(11)(PR(3))(7)X(3), and Au(13)(PR(3))(10)X(2)(3+), where X is either a halogen or a thiolate. Attributable to a compact, symmetric core and complete steric protection, each compound has a filled spherical electronic shell and a major energy gap to unoccupied states. Consequently, the exceptional stability is best described by a "noble-gas superatom" analogy. The explanatory power of this concept is shown by its application to many monomeric and oligomeric compounds of precisely known composition and structure, and its predictive power is indicated through suggestions offered for a series of anomalously stable cluster compositions which are still awaiting a precise structure determination.
authors.affiliation: Departments of Physics and Chemistry, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland.
authors.forename: Michael
authors.initials: M
authors.lastname: Walter
authors.forename: Jaakko
authors.initials: J
authors.lastname: Akola
authors.forename: Olga
authors.initials: O
authors.lastname: Lopez-Acevedo
authors.forename: Pablo D
authors.initials: PD
authors.lastname: Jadzinsky
authors.forename: Guillermo
authors.initials: G
authors.lastname: Calero
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Ackerson
authors.forename: Robert L
authors.initials: RL
authors.lastname: Whetten
authors.forename: Henrik
authors.initials: H
authors.lastname: Grönbeck
authors.forename: Hannu
authors.initials: H
authors.lastname: Häkkinen