Ag₂₉(BDT)₁₂(TPP)₄: A Tetravalent Nanocluster

Abstract

The bottom-up assembly of nanoparticles into diverse ordered solids is a challenge because it requires nanoparticles, which are often quasi-spherical, to have interaction anisotropy akin to atoms and molecules. Typically, anisotropy has been introduced by changing the shape of the inorganic nanoparticle core. Here, we present the design, self-assembly, optical properties, and total structural determination of Ag29(BDT)12(TPP)4, an atomically precise tetravalent nanocluster (NC) (BDT, 1,3-benzenedithiol; TPP, triphenylphosphine). It features four unique tetrahedrally symmetrical binding surface sites facilitated by the supramolecular assembly of 12 BDT (wide footprint bidentate thiols) in the ligand shell. When each of these sites was selectively functionalized by a single phosphine ligand, particle stability, synthetic yield, and the propensity to self-assemble into macroscopic crystals increased. The solid crystallized NCs have a substantially narrowed optical band gap compared to that of the solution state, suggesting strong interparticle electronic coupling occurs in the solid state.

Switching a Nanocluster Core from Hollow to Nonhollow

“…The presence of a single peak of Ag 25 and the absence of peaks of HSPhCOOH or its Ag-complexes are indicative of the formation of pure Ag 25 (SPhMe 2 ) 18 from Ag 44 (SPhCOOH) 30 . Similarly, Ag 44 can be recovered by exchanging SPhMe 2 ligands of Ag 25 with HSPhCOOH ( Figure S2). Fascinatingly, Ag 44 10, 11 and Ag 25 27 NCs possess unique core structures in addition to differences in core charge and the arrangement of ligands.…”

“…In overall, single phase LE transformation of Ag 44 to Ag 25 can be categorized into four stages as described below. 29 .…”

“…The typical routes for metal NC synthesis are: i) direct reduction of metal precursors in the presence of desired ligands, [22][23][24][25][26][27][28] ii) postsynthetic ligand-exchange (LE), [29][30][31][32][33][34][35] and iii) metal-exchange 15,[36][37][38][39][40][41] . Among these methods, LE has recently been widely adopted for preparing novel gold NCs [42][43][44] .…”

[Ag25(SR)18]−: The “Golden” Silver Nanoparticle

“…10 The non-hollow metallic core of Ag 25 ( Figure 3f) has not been observed with other pure mono-thiolated Ag clusters, such as Ag 44,11,12 which has a hollow icosahedral core of Ag 12 . Although there are reports of non-hollow icosahedral Ag cores, these Ag clusters are either protected with a dithiophosphate 14 18 ]¯. They are connected with 18S (from 18 thiol ligands) that can be divided into six Ag 2 S 3 groups.…”

[Ag67(SPhMe2)32(PPh3)8]3+: Synthesis, Total Structure, and Optical Properties of a Large Box-Shaped Silver Nanocluster

“…Nevertheless, the number of stable atomically monodisperse thiolate-protected silver NCs is rising, having attracted much research attention with the hope of utilizing them as a viable and cheaper alternative to gold. [25][26][27][28][29][30][31][32][33][34] A key challenge remaining for silver NCs is obtaining highly anisotropic shapes. In gold, NCs of anisotropic shapes were reported through solely thiols 35,36 and co-ligands of phosphines and thiols 37,38 .…”