Ligand and Solvent Effects on the Structural and Optical Properties of Au13L8 3+ Clusters: a Density Functional Theory Study

Abstract

Density functional theory (DFT) calculations have been performed to develop a systematic structural analysis of Au 13 L 8 3+ , where L = SCH 3 , SeCH 3 , SCH 2 OCH 3 and S(CH 2) 2 NH 2 , in order to examine the influence of different ligands. Binding energy calculations indicate that the gold core is more stabilized by the ligand in the following sequence S(CH 2) 2 NH 2 > SCH 2 OCH 3 > SeCH 3 > SCH 3. Natural bond orbital (NBO) analysis describes the interaction between the gold and the ligands, showing that the strongest electron donation occurs from a lone pair orbital on the sulfur and selenium atoms to the antibonding acceptor σ * (Au−S) and σ * (Au−Se) orbitals, respectively. The NBO analysis allowed to understand the origin of enhanced stability of the [Au 13 (S(CH 2) 2 NH 2) 8 ] 3+. Time-dependent DFT (TDDFT) calculations have been performed to simulate the optical absorption spectra of Au 13 L 8 3+ in gas phase and under the effect of solvents with different polarities. The absorption spectrum of [Au 13 (S(CH 2) 2 NH 2) 8 ] 3+ shows a spectral profile that differs considerably from the others in gas phase and which is strongly affected by the solvent.