Gas phase anion photoelectron spectroscopy and theoretical investigation of gold acetylide species.

We conducted gas phase anion photoelectron spectroscopy and density functional theory studies on a number of gold acetylide species, such as AuC2 H, AuC2 Au, and Au2 C2 H. Based on the photoelectron spectra, the electron affinities of AuC2 H, AuC2 Au, and Au2 C2 H are measured to be 1.54(±0.04), 1.60(±0.08), and 4.23(±0.08) eV, respectively. The highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps of AuC2 H and AuC2 Au are measured to be about 2.62 and 2.48 eV, respectively. It is interesting that photoelectron spectra of AuC2 H- and AuC2 Au- display similar spectral features. The comparison of experimental and theoretical results confirms that the ground-state structures of AuC2 H- , AuC2 Au- , and their neutrals are all linear with Au-C≡C-H and Au-C≡C-Au configurations. The similar geometric structures, spectral features, HOMO-LUMO gaps, and chemical bonding between AuC2 H-/0 and AuC2 Au-/0 demonstrate that Au atom behaves like H atom in these species. The photoelectron spectrum of Au2 C2 H- shows that Au2 C2 H has a high electron affinity of 4.23(±0.08) eV, indicating Au2 C2 H is a superhalogen. Further, we found an unusual similarity between the terminal Au atom of Au2 C2 H- and the iodine atom of IAuC2 H- .