Abstract:Cyclohexanethiolate-protected gold cluster Au 25 (c-HT) 18 was isolated for the first time as a minor byproduct of [Au 23 (c-HT) 16 ] ¹. Single-crystal X-ray structure analysis revealed that Au 25 (c-HT) 18 has an icosahedral Au 13 core, in sharp contrast to the face-centered cubic cores in major products such as [Au 23 (c-HT) 16 ] ¹ and Au 28 (c-HT) 20. Au 25 (c-HT) 18 prefers a neutral state to an anionic state, probably because the Au 13 core is forced to deform due to the steric hindrance between the c-HT … Show more
“…In the overall star-shaped architecture of the gold core (Fig. 4a ), Au–Au bond lengths followed the order: Au cent –Au inn > Au inn –Au inn > Au inn –Au out , as previously reported for other icosahedral Au 25 NCs 43 – 45 . Fig.…”
Crystallization of atomically precise nanoclusters is gaining increasing attention, due to the opportunity of elucidating both intracluster and intercluster packing modes, and exploiting the functionality of the resulting highly pure crystallized materials. Herein, we report the design and single-crystal X-ray structure of a superfluorinated 20 kDa gold nanocluster, with an Au25 core coated by a shell of multi-branched highly fluorinated thiols (SF27) resulting in almost 500 fluorine atoms, i.e., ([Au25(SF27)18]0). The cluster shows a switchable solubility in the fluorous phase. X-ray analysis and computational studies reveal the key role of both intracluster and intercluster F···F contacts in driving [Au25(SF27)18]0 crystal packing and stabilization, highlighting the ability of multi-branched fluorinated thiols to endow atomically precise nanoclusters with remarkable crystallogenic behavior.
“…In the overall star-shaped architecture of the gold core (Fig. 4a ), Au–Au bond lengths followed the order: Au cent –Au inn > Au inn –Au inn > Au inn –Au out , as previously reported for other icosahedral Au 25 NCs 43 – 45 . Fig.…”
Crystallization of atomically precise nanoclusters is gaining increasing attention, due to the opportunity of elucidating both intracluster and intercluster packing modes, and exploiting the functionality of the resulting highly pure crystallized materials. Herein, we report the design and single-crystal X-ray structure of a superfluorinated 20 kDa gold nanocluster, with an Au25 core coated by a shell of multi-branched highly fluorinated thiols (SF27) resulting in almost 500 fluorine atoms, i.e., ([Au25(SF27)18]0). The cluster shows a switchable solubility in the fluorous phase. X-ray analysis and computational studies reveal the key role of both intracluster and intercluster F···F contacts in driving [Au25(SF27)18]0 crystal packing and stabilization, highlighting the ability of multi-branched fluorinated thiols to endow atomically precise nanoclusters with remarkable crystallogenic behavior.
“…SCXRD showed that a new cluster, PtAu 24 (ScHex) 18 produced in entry 14, has an icosahedral MAu 12 core with six electrons . This structural motif does not follow the empirical rule that the metallic core prefers face-centered-cubic packing when bulky secondary thiols, such as ScHex, were used as the protecting ligands. , We recently reported that the pure Au 25 (ScHex) 18 cluster also possesses an icosahedral motif . These results illustrate the magic stability of the icosahedral core in MAu 24 (SR) 18 regardless of the stress from the steric repulsion between the bulky cyclohexyl ligands.…”
An efficient and selective method was developed for the synthesis of bimetallic clusters, MAu 24 L 18 (M = Pd or Pt; L = thiolates or alkynyls), by the reaction of Au(I)L oligomers with quasi-spherical superatoms [HMAu 8 (PPh 3 ) 8 ] + activated by hydride doping. This hydride-mediated conversion afforded previously known clusters MAu 24 (SC 2 H 4 Ph) 18 having an icosahedral (M@ Au 12 ) 6+ core at ∼200 mg scale, with a yield of >50%, and was successfully applied to a variety of primary thiols with good yields. Although the application to secondary and tertiary thiolates was limited, the conversion produced the novel cluster [PdAu 23 (ScC 6 H 11 ) 17 ] 0 having a poorly symmetrical, flattened (Pd@Au 12 ) 6+ core. The conversion produced the new alkynyl-protected clusters [MAu 24 (CCAr F ) 18 ] 2− (Ar F = 3,5-(CF 3 ) 2 C 6 H 3 ) having an icosahedral (M@Au 12 ) 4+ core, with a yield of >50%. The larger number of valence electrons in the M@ Au 12 core protected by alkynyls is ascribed to an increase in attractive potential of the M@Au 12 core owing to the stronger electron-withdrawing nature of alkynyls than thiolates. This simple and versatile bottom-up approach will provide an opportunity to synthesize a variety of superatoms on a large scale for the promotion of materials science based on superatoms as building units.
“…In addition to the chemical composition of the cluster, the stability, electronic structure, and functions of Au n (SR) m clusters change depending on the functional-group structure of the ligand. 9,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] For example, it has been demonstrated that properties of Au 25 (SR) 18 , such as the stability in solution, reducibility, dissociation pattern under laser irradiation, quantum yield of photoluminescence, and catalytic activity, along with other properties, differ depending on the functional-group structure of the ligand. Therefore, the selection of the ligand functional group is essential in the functionalization of Au n (SR) m clusters.…”
2-Phenylethanethiolate (PET) and 4-tert-butylbenzenethiolate (TBBT) are the most frequently used ligands in the study of thiolate (SR)-protected metal clusters. However, the effect of difference in the functional group between these ligands on the fundamental properties of the clusters has not been clarified. We synthesized [Au 24 Pt(TBBT) 18 ] 0 , which has the same number of metal atoms, number of ligands, and framework structure as [Au 24 Pt(PET) 18 ] 0 , by replacing ligands of [Au 24 Pt(PET) 18 ] 0 with TBBT. It was found that this ligand exchange is reversible unlike the case of other metal-core clusters. A comparison of the geometrical/electronic structure and stability of the clusters between [Au 24 Pt(PET) 18 ] 0 and [Au 24 Pt(TBBT) 18 ] 0 revealed three things with regard to the effect of ligand change from PET to TBBT on [Au 24 Pt(SR) 18 ] 0 : (1) the induction of metal-core contraction and Au-S bond elongation, (2) no substantial effect on the HOMO-LUMO gap but a clear difference in optical absorption in the visible region, and (3) the decrease of stabilities against degradation in solution and under laser irradiation. By using these two clusters as model clusters, it is expected that the effects of the structural difference of ligand functionalgroups on the physical properties and functions of clusters, such as catalytic ability and photoluminescence, would be clarified. † Electronic supplementary information (ESI) available: Bond lengths, peak positions in SWV curves, additional schemes, characterization of a precursor, photograph of TLC and crystal, ESI mass and XPS spectra, HPLC chromatogram, crystal data of the product. CCDC 1944945. For ESI and crystallographic data in CIF or other electronic format see
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