Probing the electronic structure and Au—C chemical bonding in AuCn− and AuCnH− (n = 2, 4, and 6) using high-resolution photoelectron spectroscopy

Abstract

We report a joint photoelectron spectroscopy and theoretical study on AuC4−, AuC6−, and AuCnH− (n = 2, 4, and 6) using high-resolution photoelectron imaging and ab initio calculations. The ground state of AuC2H−, AuC4H−, and AuC6H− is found to be linear, while that of AuC4− and AuC6− is bent. All the species are found to be linear in their neutral ground states. The electron affinities (EAs) are measured to be 3.366(1) and 3.593(1) eV for AuC4 and AuC6, respectively. Both bending and stretching frequencies are resolved in the spectra of AuC4− and AuC6−. High-resolution data of AuCnH− reveal major vibrational progressions in the Au—C stretching and bending modes. AuC2H− has a ground state stretching frequency of 445(10) cm−1 and a bending frequency of 260(10) cm−1; AuC4H− has a ground state stretching frequency of 340(10) cm−1; AuC6H− has a ground state stretching frequency of 260(10) cm−1 and a bending frequency of 55(10) cm−1. The EAs are measured to be 1.475(1), 1.778(1), and 1.962(1) eV for AuC2H, AuC4H, and AuC6H, respectively. The strength of the Au—C bond decreases as the number of carbon atoms increases. The current study provides a wealth of electronic structure information about AuC4−, AuC6−, and AuCnH− (n = 2, 4, and 6) and their corresponding neutrals.