Because
of the typical instability of copper nanoclusters, atom-precise
structural elucidation of these nanoclusters has remained elusive.
Herein, we report an air- and moisture-stable 23-copper nanocluster
(SD/Cu23a or SD/Cu23b) isolated from the
reaction of Cu(CF3COO)2,
t
BuCCH, Cu powder, and Ph2SiH2 using a gradient reduction (CuII → CuI → Cu0) strategy (GRS), which is competent for
controlling the kinetics of the reduction reaction, thus avoiding
formation of pure CuI complexes or large Cu0 nanoparticles. The solid-state structure of the Cu23 nanocluster
shows a rare [Cu4]0 tetrahedral kernel surrounded
by an outer Cu19 shell, which is protected by
t
BuCC– and CF3COO– ligands. The Cu23nanocluster is
a rare four-electron superatom with a 1S21P2 electronic shell closure and can be crystallized in two polymorphs
(R3c and R3̅)
depending on the solvent used. The crystallization of SD/Cu23a in the R3c space group is mainly
governed by van der Waals forces and C–H···F
interactions, whereas additional intermolecular C–H···Clchloroform interactions are responsible for the R3̅ space group of SD/Cu23b. This work not only
shows the ingenuity of a gradient reduction strategy for the synthesis
of copper nanoclusters but also provides a better fundamental understanding
of how to produce the polymorphic copper nanoclusters in a precisely
tunable fashion.
Assembly of small clusters into rigid bodies with precise shape and symmetry has been witnessed by the significant advances in cluster-based metal-organic frameworks (MOFs), however, nanosized silver cluster based MOFs remain largely unexplored. Herein, two anion-templated silver clusters, CO3 @Ag20 and SO4 @Ag22 , were ingeniously incorporated into a 2D sql lattice (1, [CO3 @Ag20 (iPrS)10 (NO3 )8 (DMF)2 ]n ) and an unprecedented 3D two-fold interpenetrated dia network (2, [SO4 @Ag22 (iPrS)12 (NO3 )6 ⋅2 NO3 ]n ), respectively, under mild solvothermal conditions. Their atomically precise structures were confirmed by single-crystal X-ray diffraction analysis and further consolidated by IR spectroscopy, thermogravimetric analysis (TGA), and elemental analysis. Each drum-like CO3 @Ag20 cluster is extended by twelve NO3 (-) ions to form the 2D sql lattice of 1, whereas each ball-shaped SO4 @Ag22 cluster with a twisted truncated tetrahedral geometry is pillared by four [Ag6 (NO3 )3 ] triangular prisms to form the 3D interpenetrated dia network of 2. Notably, 2 is the first interpenetrated 3D MOF constructed from silver clusters. These results demonstrate the dual role of the anions, which not only internally act as anion templates to induce the formation of silver thiolate clusters but also externally extend the cluster units into the rigid networks. The photoluminescent and electrochemical properties of 2 are discussed in detail.
The structural transformation of high-nuclearity silver clusters from one to another induced by specific stimuli is of scientific significance in terms of both cluster synthesis and reactivity. Herein, we report two silver-thiolate clusters, [Mo6O22@Ag44] and [Mo8O28@Ag50], which are templated by isopolymolybdates inside and covered by iPrS− and PhCOO− ligands on the surfaces. Amazingly, the [Mo8O28@Ag50] can be transformed from [Mo6O22@Ag44] by adding PhCOOH which increases the degree of condensation of molybdates template from Mo6O228- to Mo8O288-, then enlarging the outer silver shell from Ag44 to Ag50. The evolution of solution species revealed by time-dependent electrospray ionization mass spectrometry (ESI-MS) suggests a breakage-growth-reassembly (BGR) transformation mechanism. These results not only provide a combined assembly strategy (anion-template + induced transformation) for the synthesis of silver-thiolate clusters but also help us to better understand the complex transformation process underpinning the assembly system.
Isomers with minimal structural dissimilarities are promising research objects to obtain a comprehensive understanding of structure−property relationships; however, comparability of isomeric structures is a prerequisite. Herein, two quasi-structurally isomeric 13-nuclei copper nanoclusters (Cu NCs) (Cu13a and Cu13b) containing highly similar Cu 13 kernels and different arrangements of peripheral ligands were obtained using a solvent-induced strategy. The exotic chloride ion is shown to play a prominent role in inducing the selective formation of two quasi-isomers, where the comparative study to establish a structure−property relationship was realized. Due to the charge transition from chlorine to the copper core (X (Cl) M (Cu) CT), the molecular oxygen activation of Cu13a showed higher singlet oxygen ( 1 O 2 ) and lower superoxide radical (O 2•− ) yields compared to those of Cu13b, which gives it better catalytic selectivity for the 1 O 2 involved selective oxidation of sulfides. The present work not only offers a controllable strategy for the rational design and synthesis of quasi-structurally isomeric Cu NCs but also provides a pathway to boost catalytic selectivity by a halogen to metal core charge transition.
Chiral
assembly of metal nanoparticles (NPs) into complex superstructures
has been widely studied, but their formation mechanisms still remain
mysterious due to the lack of precise structural information from
the metal–organic interface to metallic kernel. As “molecular
models” of metal NPs, atomically precise metal nanoclusters
(NCs) used in the assembly of a macroscale superstructure will provide
details of microscopic structure for deep understanding of such highly
sophisticated assemblies; however, chiral superstructures have not
been realized starting from achiral metal NCs with atomic precision.
Herein, we report the supramolecular assembly of a water-soluble silver
NC ((NH4)9[Ag9(mba)9],
H2mba = 2-mercaptobenzoic acid, abbreviated as Ag9–NCs hereafter) into chiral hydrogels induced by the coordination
of secondary metal ions. Single crystal X-ray diffraction reveals
the triskelion-like structure of Ag9–NCs with a
pseudochiral conformation caused by special arrangement of the peripheral
mba2– ligands. The enantioselective orientation
of the peripheral carboxyl group facilitates the assembly of Ag9–NCs into nanotubes with a chiral cubic (I*) lattice when coordinating to Ba2+. The nanotubes can
further intertwine into one-dimensional chiral nanobraids with a preferred
left-handed arrangement. These multiple levels of chirality can be
tuned by drying, during which the I* phase is missing
but the chiral entanglement of the nanotubes is enhanced. Through
the gelation of atomically precise, achiral NCs coordination of secondary
metal ions, chiral amplification of superstructures was realized.
The origination of the chirality at different length scales was also
discussed.
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