Probing the structures and bonding of auropolyynes, Au-(C≡C) -Au^- (n = 1-3), using high-resolution photoelectron...

We report an investigation of a series of auropolyynes, Au-(C≡C) -Au^- (n = 1-3), using high-resolution photoelectron imaging and ab initio calculations. Vibrationally resolved photoelectron spectra are obtained, allowing the electron affinities of Au-(C≡C) -Au to be accurately measured as 1.651(1), 1.715(1), and 1.873(1) eV for n = 1-3, respectively. Both the Au-C symmetric stretching and a bending vibrational frequency are observed for each neutral auropolyyne. Theoretical calculations find that the ground state of Au₂C₂ ^- has a linear acetylenic Au-C≡C-Au^- structure, whereas the asymmetric Au-Au-C≡C^- structure is a low-lying isomer. However, for Au₂C₄ ^- and Au₂C₆ ^-, our calculations show that the asymmetric Au-Au-(C≡C) ^- isomers are the global minima and the Au-(C≡C) -Au^- symmetric structures become low-lying isomers. All the asymmetric Au-Au-(C≡C) ^- isomers are found computationally to have much higher electron binding energies and are not accessible at the detachment photon energies used in the current study. For neutral Au₂C₂ , the Au-(C≡C) -Au auropolyyne structures are found to be the global minima for n = 1-3. The electronic structures and bonding for Au-(C≡C) -Au (n = 1-3) are compared with the corresponding Au-(C≡C) and Au-(C≡C) -H species.