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 (Au₁₅ vs Au₁₄) 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.