Atomically Precise Site-Specific Tailoring and Directional Assembly of Superatomic Silver Nanoclusters

Convenient
generation of stable superatomic silver clusters and
their systematic site-specific tailoring and directional assembly
present an enduring and significant challenge. In this work, we prepared
a face-centered cubic (fcc) array of Ag14 superatoms protected
by face-capping 1,2-dithiolate-o-carborane (C2B10H10S2) ligands, each produced
from 1-thiol-o-carborane in crystallization with
simultaneous reduction of Ag+ to Ag0. We find
that the corner N-donor ligands contribute predominately to the stability
and luminescence of the Ag14 superatom. As the first-formed
nanocluster [Ag14(C2B10H10S2)6(CH3CN)8]·4CH3CN (NC-1) with labile vertex-coordinated CH3CN ligands is highly unstable, monodendate pyridine ligands
were used to replace these CH3CN species site-specifically,
giving [Ag14(C2B10H10S2)6(pyridine/p-methylpyridine)8] (NCs-2,3) in gram scale with its core structure
intact, which features ultrastability up to 150 °C in air. Moreover,
using bidentate N-containing ligands to bridge the superatomic Ag14 building blocks, we constructed an unprecedented hierarchical
series of 1D-to-3D superatomic silver cluster-assembled materials
(SCAM-1,2,3,4), and SCAM-4 is air-stable
up to 220 °C. Furthermore, this series of stable solid-state
superatomic-nanocluster materials exhibit tunable dual emission with
wide-range thermochromism. The present study constitutes a major step
toward the development of ligand-modulation of the structure, stability,
assembly, and functionality of superatomic silver nanoclusters.