Adsorption of multiple NO molecules on Au10- and Au9Zn- planar clusters. A comparative DFT study.

Abstract

The doping of atomic clusters with transition-metal atoms modifies to a lesser or greater extent the catalytic properties of the pure forms. Here we study by means of density functional theory (DFT) the adsorption of up to six NO molecules on Au10- and Au9Zn- clusters, both with well-tested D3h planar geometry, to learn how precise modifications of the atomic and electronic environment, namely one atom and a valence electron, affect the bonding of multiple NO molecules to anionic gold clusters. First, we confirm that these clusters have D3h symmetry as determined by L. S. Wang and coworkers using photoelectron spectroscopy experiments [Kulichenko et al., J. Phys. Chem. A, 2021, 125, 4606]. Second, we verify that Au10(NO)n- with n ≤ 6 does not form adsorbed (NO)2 dimers, as realized by the experiments of Ma and coworkers [Ma et al., Phys. Chem. Chem. Phys., 2020, 22, 25227] using a mini flow-tube reactor at 150 K. Third, we discover that the ground state of the doped Au9Zn(NO)6- compound forms a (NO)2cis-dimer bridging two non-corner Au atoms of the Au9Zn(NO)4- compound. The discussion of adsorption energies, spin multiplicities, bond lengths, charge trends, vibrational strength frequencies of adsorbed NO's, and projected density of states (PDOS), brings additional testable differences between Au10(NO)n- and Au9Zn(NO)n- compounds (n ≤ 6).