Probing the electronic structure and Au-C bonding in AuC 2 n H ( n = 4-7) using photoelectron imaging spectroscopy and quantum chemical calculations.

We report a combined experimental and theoretical study on the structures and chemical bonding of AuC 2 n H ( n = 4-7) using photoelectron imaging and quantum chemical calculations. All the ground states of anions and neutral AuC 2 n H have a linear geometry. The electron affinities (EAs) are measured to be 2.063(5), 2.157(5), 2.220(5), and 2.267(5) eV for AuC 2 n H, n = 4-7, respectively. The photoelectron imaging data of AuC 8 H - and AuC 10 H - reveal major vibrational progressions in the Au-C stretching modes. The ground state stretching frequencies of the titled neutral molecules are 226, 193, 177, and 128 cm -1 , respectively. By comparing the experimental β value and theoretical molecular orbital analysis, we confirm that the CAM-B3LYP method is more suitable for describing the properties of such unsaturated long chains organogold clusters. The experimental and CAM-B3LYP methods give a big picture of the trend in EAs of AuC 2 n H. This shows that the EA value becomes larger with an increase in the carbon chain length, and it also shows a slow increment for larger n . The NRT analysis shows that the change of the Au-C bond order is not obvious as the number of carbon atoms increases, and the covalent character dominates the Au-C chemical bonds in these neutral species. The current study provides a wealth of electronic structure information about long-chain AuC 2 n H - ( n = 4-7) and their corresponding neutral counterparts.