Probing the structures and bonding of auropolyynes, Au—(C≡C)n—Au− (n = 1–3), using high-resolution photoelectron imaging

We report an investigation of a series of auropolyynes, Au—(C≡C)n—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)n—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)n− isomers are the global minima and the Au—(C≡C)n—Au− symmetric structures become low-lying isomers. All the asymmetric Au—Au—(C≡C)n− isomers are found computationally to have much higher electron binding energies and are not accessible at the detachment photon energies used in the current s...