Homoleptic Alkynyl‐Protected Gold Nanoclusters: Au44(PhC≡C)28 and Au36(PhC≡C)24

For the first time total structure determination of homoleptic alkynyl‐protected gold nanoclusters is reported. The nanoclusters are synthesized by direct reduction of PhC≡CAu, to give Au₄₄(PhC≡C)₂₈ and Au₃₆(PhC≡C)₂₄. The Au₄₄ and Au₃₆ nanoclusters have fcc‐type Au₃₆ and Au₂₈ kernels, respectively, as well as surrounding PhC≡C‐Au‐C₂(Ph)Au‐C≡CPh dimeric “staples” and simple PhC≡C bridges. The structures of Au₄₄(PhC≡C)₂₈ and Au₃₆(PhC≡C)₂₄ are similar to Au₄₄(SR)₂₈ and Au₃₆(SR)₂₄, but the UV/Vis spectra are different. The protecting ligands influence the electronic structures of nanoclusters significantly. The synthesis of these two alkynyl‐protected gold nanoclusters indicates that a series of gold nanoclusters in the general formula Au_x (RC≡C)_y as counterparts to Au_x (SR)_y can be expected.     

A Ligand‐Protected Golden Fullerene: The Dipyridylamido Au328+ Nanocluster

A golden fullerene Au₃₂ cluster has been synthesized with amido and phosphine ligands as the protecting agents. Single‐crystal X‐ray structural analysis revealed that this gold nanocluster, [Au₃₂(Ph₃P)₈(dpa)₆] (SbF₆)₂ (Hdpa=2,2′‐dipyridylamine), has a stable pseudo‐I_h Au₃₂⁸⁺ core with S₆ symmetry, which features an Au₁₂@Au₂₀ Keplerate cage co‐protected by Ph₃P and dpa ligands. Quantum‐chemical studies were conducted to elucidate the origin of the special stability of this cluster, and suggest that it is electronically stabilized through metal–ligand interactions.     

Optical Spectroscopy of the Au4+ Cluster: The Resolved Vibronic Structure Indicates an Unexpected Isomer

Knowledge of the geometric and electronic structure of gold clusters and nanoparticles is vital for understanding their catalytic and photochemical properties at the molecular level. In this study, we report the vibronic optical photodissociation spectrum of cold and mass‐selected Au₄⁺ clusters measured at a resolution high enough to allow for comparison with Franck–Condon simulations of the excited state transitions based on time‐dependent density functional theory calculations. The three vibrational frequencies identified for the lowest‐lying optically accessible excited state at 2.17 eV stem from the Y‐shaped isomer (C_2v) and not from the rhombic isomer (D_2h) considered to be the ground state structure of Au₄⁺. This study demonstrates that an analysis of low‐resolution electronic spectra by calculations of vertical transitions alone is not sufficient for a reliable isomer assignment of such metal clusters.