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 Au-30(S-tBu)(18). While the structure of Au30S(S-tBu)(18) with 19 sulfur atoms has been reported, the crystal structure of Au-30(S-tBu)(18) without the mu(3)-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 Au-30(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.