Golden Opportunity: A Clickable Azide-Functionalized [Au₂₅(SR)₁₈]⁻ Nanocluster Platform for Interfacial Surface Modifications

Abstract

Ultrasmall atomically precise monolayerprotected gold thiolate nanoclusters are an intensely researched nanomaterial framework, but there is a lack of a system that can be directly synthesized and undergo interfacial surface chemistry. We report an [Au 25 (SCH 2 CH 2 -p-C 6 H 4 -N 3 ) 18 ] − nanocluster platform with azide moieties appended onto each surface ligand. The structure of this surface reactive cluster has been confirmed by single-crystal X-ray crystallography, mass spectrometry and ultraviolet visible, infrared and nuclear magnetic resonance spectroscopies. We show that all surface azide moieties are amenable to cluster-surface strain-promoted alkyne−azide cycloaddition chemistry with a strained cyclooctyne, opening this as a new platform to allow functional, postassembly surface modifications to this very prominent nanocluster.

Toward Controlling the Electronic Structures of Chemically Modified Superatoms of Gold and Silver

“…Table 2 lists the magic Au clusters having the cores of Au 4 (2e), Au 11 (8e), Au 13 (8e), Au 79 (58e), Au 107 (81e), and Au 114 (84e). [ 9–62 ] The ubiquitous nature of Au 4 (2e), Au 11 (8e) and Au 13 (8e) regardless of the ligands, indicates their inherent stability. SCXRD analyses showed that the metallic cores take isotropic structures such as icosahedron (Ih) and decahedron (Dh) (Table 2).…”

“…When the degree of distortion exceeds a critical level, the superatom transforms into a structural isomer which has distinctly different atomic packings. Namely, the superatomic cores of [(Au/Ag) x L y ] z can take isomeric structures depending on their relative stabilities determined by the nature of L. Au 13 (8e) generally prefers an Ih structure as demonstrated in Table 2, [ 17,37–55 ] but takes a face‐centered cubic (FCC)‐based structure in [Au 23 (S c Hex) 16 ] − ( c HexSH = cyclohexanethiol), Au 24 (SAdm) 16 (AdmSH = 1‐adamantanethiol), and [Au 25 (SPG) 18 ] − (PGSH = N ‐(2‐mercaptopropionyl)glycine) ( Figure a). [ 177–179 ] The formation of an FCC Au 13 (8e) superatom is ascribed to the steric repulsion between the thiolate ligands having a bulky α‐carbon.…”

A Survey of Strain‐Promoted Azide–Alkyne Cycloaddition in Polymer Chemistry

“…The resulting polymers were precipitated to form nanoparticles and used for in vitro and in vivo imaging. Using smaller nanostructures, Workentin and co‐workers showed that modification of ligands on gold nanoclusters can be carried out using SPAAC [76] . The gold clusters were stabilized with a library of 18 different azide‐functionalized thiol ligands, which subsequently underwent a quantitative reaction with ( Z )‐cyclooct‐1‐ene‐5‐yne.…”

“…Using smaller nanostructures, Workentin andc o-workerss howed that modification of ligandso ng old nanoclusters can be carried out using SPAAC. [76] The gold clusters were stabilized with al ibrary of 18 different azide-functionalized thiol ligands, which subsequently underwent aq uantitative reaction with (Z)-cyclooct-1-ene-5-yne. In addition to nanoparticles,t he surfaceo f block copolymer micelles has been decorated with 4-dibenzocyclooctynol to enable further functionalization with various azide-modified structures via SPAAC.…”

Highly Strained Unsaturated Carbocycles

“…[120] In 2019, Workentin and co-workers reported the synthesis of (Z)-cyclooctene-5-yne (115) (116). [121] With the azide group on the surface of the nanoparticles, it allows for postassembly modifications of these. Due to the highly strained nature of 115, the reaction is complete in under 5 minutes in different solvents, giving the triazole 117 in 96 % yield.…”