Green Gold: Au₃₀(S‑<i>t</i>‑C₄H₉)₁₈ Molecules

Here, we report the synthesis and separation of Au₃₀(<i>tert</i>-thiol)₁₈ (<i>tert</i>-thiol = <i>tert-</i>butanethiol and 1-adamantanethiol) from a mixture of sizes of bulky-ligated nanoparticles. With precisely 30 gold metal atoms and 18 tertiary butyl ligands, this new 30 Au atom molecule is assigned a formula based on results obtained in high-resolution electrospray ionization (ESI) mass spectrometry. UV-vis-NIR spectroscopy shows a distinct electronic transition featured at 620 nm, with a valley in the green wavelength 520–570 nm region, explaining the green appearance. This lack of absorbance in the green region is uncommon, and therefore, metal nanoparticles of green color are extremely rare. Its optical band gap, 1.76 eV is much different than the 1.3 eV reported for Au₂₅­(SR)­₁₈. We report its reproducible direct synthesis (∼10 mg) in a one-pot reaction, with two different ligands. Because of the unique optical properties and altered-discrete sizes, there is a fundamental need for structural analysis of this nanoparticle

Single Crystal XRD Structure and Theoretical Analysis of the Chiral Au₃₀S(S‑<i>t</i>‑Bu)₁₈ Cluster

Au₃₀S­(S-<i>t</i>-Bu)₁₈ cluster, related closely to the recently isolated “green gold” compound Au₃₀(S-<i>t</i>-Bu)₁₈, has been structurally solved via single-crystal XRD and analyzed by density functional theory calculations. The molecular protecting layer shows a combination of monomeric (RS-Au-SR) and trimeric (RS-Au-SR-Au-SR-Au-SR) gold–thiolate units, bridging thiolates, and a single sulfur (sulfide) in a novel μ₃-coordinating position. The chiral gold core has a geometrical component that is identical to the core of the recently reported Au₂₈(SPh-<i>t</i>-Bu)₂₀. Both enantiomers of Au₃₀S­(S-<i>t</i>-Bu)₁₈ are found in the crystal unit cell. The calculated CD spectrum bears a close resemblance to that of Au₂₈(SPh-<i>t</i>-Bu)₂₀. This is the first time when two structurally characterized thiol-stabilized gold clusters are found to have such closely related metal core structures and the results may increase understanding of the formation of gold clusters when stabilized by bulky thiolates

Au₂₄(SAdm)₁₆ Nanomolecules: X‑ray Crystal Structure, Theoretical Analysis, Adaptability of Adamantane Ligands to Form Au₂₃(SAdm)₁₆ and Au₂₅(SAdm)₁₆, and Its Relation to Au₂₅(SR)₁₈

Here we present the crystal structure, experimental and theoretical characterization of a Au₂₄(SAdm)₁₆ nanomolecule. The composition was verified by X-ray crystallography and mass spectrometry, and its optical and electronic properties were investigated via experiments and first-principles calculations. Most importantly, the focus of this work is to demonstrate how the use of bulky thiolate ligands, such as adamantanethiol, versus the commonly studied phenylethanethiolate ligands leads to a great structural flexibility, where the metal core changes its shape from five-fold to crystalline-like motifs and can adapt to the formation of Au_24±1(SAdm)₁₆, namely, Au₂₃(SAdm)₁₆, Au₂₄(SAdm)₁₆, and Au₂₅(SAdm)₁₆. The basis for the construction of a thermodynamic phase diagram of Au nanomolecules in terms of ligands and solvent features is also outlined

Crystal Structure and Theoretical Analysis of Green Gold Au₃₀(S‑<i>t</i>Bu)₁₈ Nanomolecules and Their Relation to Au₃₀S(S‑<i>t</i>Bu)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-<i>t</i>Bu)₁₈. While the structure of Au₃₀S­(S-<i>t</i>Bu)₁₈ with 19 sulfur atoms has been reported, the crystal structure of Au₃₀(S-<i>t</i>Bu)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-<i>t</i>Bu)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

Crystal Structure and Theoretical Analysis of Green Gold Au₃₀(S‑<i>t</i>Bu)₁₈ Nanomolecules and Their Relation to Au₃₀S(S‑<i>t</i>Bu)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-<i>t</i>Bu)₁₈. While the structure of Au₃₀S­(S-<i>t</i>Bu)₁₈ with 19 sulfur atoms has been reported, the crystal structure of Au₃₀(S-<i>t</i>Bu)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-<i>t</i>Bu)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