Surface Coordination of Multiple Ligands Endows N‐Heterocyclic Carbene‐Stabilized Gold Nanoclusters with High Robustness and Surface Reactivity

Abstract

Deciphering the molecular pictures of the multi‐component and non‐periodic organic‐inorganic interlayer is a grand technical challenge. Here we show that the atomic arrangement of hybrid surface ligands on metal nanoparticles can be precisely quantified through comprehensive characterization of a novel gold cluster, Au44(iPr2‐bimy)9(PA)6Br8 (1), which features three types of ligands, namely, carbene (1,3‐diisopropylbenzimidazolin‐2‐ylidene, iPr2‐bimy), alkynyl (phenylacetylide, PA), and halide (Br), respectively. The delicately balanced stereochemical effects and bonding capabilities of the three ligands give rise to peculiar geometrical and electronic structures. Remarkably, despite its complex and highly distorted surface structure, cluster 1 exhibits unusual catalytic properties and yet it is highly stable, both chemically and thermally. Moreover, rich reactive sites on the cluster surface raise the prospect of bio‐compatibility (as it can be functionalized to yield water‐soluble derivatives) and bio‐applications.

Chemically Modified Gold/Silver Superatoms as Artificial Elements at Nanoscale: Design Principles and Synthesis Challenges

“…Recent examples are [Au 20 (PPh 3 ) 13 H 3 ] 3+ , [Au 22 (dppo) 6 H 4 ] 2+ (Figure 10a), 107−109 and Au 44 (NHC-1) 9 (CCPh) 6 Br 8 (Figure 10b). 110 The Au 44 (NHC-1) 9 (CCPh) 6 Br 8 cluster catalyzed the hydration reaction of terminal alkynes using the exposed surface sites without loss of activity after at least five times of recycling. 110 These systems provide an ideal platform for attaining a molecular-level understanding of the catalytic mechanism of superatoms.…”

From Au11 to Au13: Tailored Synthesis of Superatomic Di-NHC/PPh3-Stabilized Molecular Gold Nanoclusters

“…Furthermore, the electronic properties of the thiolate ligands cannot be very extensively varied, thus hampering the control over AuNC properties, such as the electronic structure of the cluster, its energy levels, and in ultimate analysis its photophysical behavior . Consequently, alternative ligand systems are currently being investigated to stabilize AuNCs, such as phosphines (PR 3 ), − alkynyls, − and N-heterocyclic carbenes (NHCs). − The latter in particular have been recently shown to be very useful for AuNCs stabilization since very strong Au-NHC bonds can be established. ,, Nowadays, a great number of NHC ligands are available, featuring steric and electronic properties that can be extensively and independently varied for this purpose. − …”

“… 15 Consequently, alternative ligand systems are currently being investigated to stabilize AuNCs, such as phosphines (PR 3 ), 16 − 25 alkynyls, 26 − 32 and N-heterocyclic carbenes (NHCs). 32 − 39 The latter in particular have been recently shown to be very useful for AuNCs stabilization since very strong Au-NHC bonds can be established. 35 , 40 , 41 Nowadays, a great number of NHC ligands are available, featuring steric and electronic properties that can be extensively and independently varied for this purpose.…”

Synthesis and Characterization of a Monodentate N-Heterocyclic Carbene-Protected Au11-Nanocluster via Reduction with KC8

“…5,6 In 2019, our group reported the first use of NHCs to protect Au 11 4 and Au 13 3 nanoclusters. Since then, our group along with Han, Zang, Tsukuda, Mak, and Zheng have reported the synthesis of Au 10 , 7 Au 11 , 8 Au 13 , 8−10 Au 23 , 11 Au 24 , 12,13 Au 25 , 13−15 and Au 44 16 nanoclusters protected by NHCs.…”