From a Golden Alkynyl Knot to a Thiolate Analogue: Computational Design of a Stable Trefoil-Knotted [Au(SR)] 14 Architecture

While homoleptic gold(I)-alkynyl complexes with trefoil-knotted architectures are known, their gold(I)-thiolate analogues have remained elusive. This work addresses this gap through the computational design of a series of trefoil-knotted [Au(SR)] n complexes ( n = 12–16). Systematic density functional theory (DFT) calculations, evaluated across multiple functionals and basis sets, consistently identify the 14-gold-atom complex [Au(SR)] 14 as the most thermodynamically stable structure, in contrast to the 15-unit framework of its Au(I)-alkynyl counterpart. Detailed geometric parameter analysis and Interaction Region Indicator (IRI) visualization reveal that the superior stability of the trefoil-knotted [Au(SR)] 14 stems from an optimal balance among near-linear RS–Au–SR coordination, favorable aurophilic interactions, and minimized steric repulsion. Furthermore, the calculated formation energies for three conceivable assembly pathways suggest that the reaction combining two [Au(SR)] 4 units with one [Au(SR)] 6 unit is the most thermodynamically favorable route for the synthesis. Comparative electronic structure and spectroscopic analysis demonstrates that the distinct ligand fields (alkynyl vs thiolate) and nuclearity (Au 15 vs Au 14 ) lead to significantly different electronic and optical properties between the trefoil-knotted [Au(SR)] 14 and [Au(C≡CR)] 15 . This study proposes [Au(SR)] 14 as a viable yet-to-be-synthesized member of the trefoil-knotted gold(I) complex family.