Crystal Structure and Theoretical Analysis of Green Gold Au₃₀(S‑tBu)₁₈ Nanomolecules and Their Relation to Au₃₀S(S‑tBu)₁₈

We report the complete X-ray crystallographic structure as determined through single-crystal X-ray diffraction and a thorough theoretical analysis of the green gold Au₃₀(S-tBu)₁₈. While the structure of Au₃₀S­(S-tBu)₁₈ with 19 sulfur atoms has been reported, the crystal structure of Au₃₀(S-tBu)₁₈ without the μ₃-sulfur has remained elusive until now, though matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) and electrospray ionization mass spectrometry (ESI-MS) data unequivocally show its presence in abundance. The Au₃₀(S-tBu)₁₈ nanomolecule not only is distinct in its crystal structure but also has unique temperature-dependent optical properties. Structure determination allows a rigorous comparison and an excellent agreement with theoretical predictions of structure, stability, and optical response.