Quantum-chemical study of the effect of ligands on the structure and properties of gold clusters

Abstract

The structures of [Au₄(dpmp)₂X₂]²⁺clusters, where Х =–C≡CH,–СН₃,–SCH₃,–F,–Cl,–Br,–I, dpmp is bis((diphenylphosphino)methyl)(phenyl)phosphine, are calculated at the level of density functional theory with the PBE functional and a modified Dirac–Coulomb–Breit Hamiltonian in an all-electron basis set (Λ). Using the example of [Au₄(dpmp)₂(С≡CС₆Н₅)₂]²⁺, the interatomic distances and bond angles calculated by means of PBE0/LANL2DZ, TPSS/LANL2DZ, TPSSh/LANL2DZ, and PBE/Λ are compared to X-ray crystallography data. It is shown that PBE/Λ yields the most accurate calculation of the geometrical parameters of this cluster. The ligand effect on the electronic stability of a cluster and the stability in reactions of decomposition into different fragments is studied, along with the capability of ligand exchange. Stability is predicted for [Au₄(dpmp)₂F₂]²⁺ and [Au₄(dpmp)₂(SCH₃)₂]²⁺, while [Au₄(dpmp)₂I₂]²⁺ cluster is unstable and its decomposes into two identical fragments is supposed.