Investigation On Interaction Between Ligands And A Tetrahedral Gold Cluster Au₂₀ By Density Functional Theory

In recent five years, experimentalists and theoreticians have paid much attention to structures and properties of the tetrahedral gold cluster Au20. However, lack of experiment parameters of geometrical structures of the cluster makes it a challenge for accurate calculations for a long time. A feasible scheme for reasonable selection of exchange-correlation functions is a systemic comparison of calculation results with experimental values of gold-containing diatomic molecules. Here, Xαwas applied for geometry optimizations and VPW91 was used for energy calculations. This new approach can be expressed as Xα//VPW91.It was found that phosphine ligand (PH3) prefers apex coordination since there is a remarkable smaller Pauli repulsion between the ligand and the gold cluster Au20 comparing with the case of inner coordination. Electron donors with lone electrons pair in apex coordination significantly destroy the geometry of the center gold cluster Au20 core since there is a L Auσdonation from lone pair orbitals in ligands to a virtual orbital 16a1 of the cluster which is sensitive to the geometry of the gold cluster, and a strong pauli repulsion derived from lone electron pair in ligands to the gold cluster core. Radical ligands in apex coordination hardly change the geometry of the center gold cluster Au20 core without above interactions with the cluster.