Theoretical study on the structure and properties of Au⋯Au interlocking gold(i) thiolate[2]catenanes

Abstract

In this work, a series of homoleptic monocyclic and [2]catenanes gold(I) thiolates were studied by DFT and TD-DFT methods to analyze the relationship between structure and property. The results reveal that the increase of Au–S–Au bond angles in Au11 and Au12 makes the [2]catenanes more planar than the monocyclic molecules. The smaller Au⋯Au contacts tighten the overall structure and enhance its geometrical stability. There is a positive correlation between the Au percentage in the frontier molecular orbitals and the orbital energy levels for both monocyclic molecules and [2]catenanes. The HOMO levels of the [2]catenanes are higher than those of the monocyclic molecules, which may be caused by stronger Au⋯Au Pauli repulsion. Differences in size and metallophilic interactions are responsible for the different absorption spectra of the complexes, and the electronic spectral redshift of the [2]catenanes is consistent with their higher HOMO energy levels. The results of energy decomposition analysis indicate that electrostatic interaction and orbital interaction are the main driving forces of molecular formation. In [2]catenanes, Pauli repulsion and steric interaction can be balanced. The calculated results of interaction energy and stabilization energy suggest that [2]catenanes are very stable. The calculated reaction enthalpies indicate that the chemical stabilization of [2]catenanes decreased in the order of Au12, Au11, and Au10.