Quan-Ming Wang

Au20 nanocluster protected by hemilabile phosphines

A novel phosphine-protected Au(20) nanocluster was isolated through the reduction of Au(PPhpy(2))Cl by NaBH(4) (PPhpy(2) = bis(2-pyridyl)-phenylphosphine). Its composition was determined to be [Au(20)(PPhpy(2))(10)Cl(4)]Cl(2), and single crystal X-ray structural analysis revealed that the Au(20) core can be viewed as being generated from the fusion of two Au(11) clusters via sharing two vertices. Optical absorption spectroscopy indicated this Au(20) has a large HOMO-LUMO gap (E(g) ≈ 2.24 eV). This is the first example of a ligand-protected gold nanocluster with a core generated from incomplete icosahedral Au(11) building units.

A Chiral Gold Nanocluster Au20 Protected by Tetradentate Phosphine Ligands

The chirality of a gold nanocluster can be generated from either an intrinsically chiral inorganic core or an achiral inorganic core in a chiral environment. The first structural determination of a gold nanocluster containing an intrinsic chiral inorganic core is reported. The chiral gold nanocluster [Au20(PP3)4]Cl4 (PP3=tris(2-(diphenylphosphino)ethyl)phosphine) has been prepared by the reduction of a gold(I)-tetraphosphine precursor in dichloromethane solution. Single-crystal structural determination reveals that the cluster molecular structure has C3 symmetry. It consists of a Au20 core consolidated by four peripheral tetraphosphines. The Au20 core can be viewed as the combination of an icosahedral Au13 and a helical Y-shaped Au7 motif. The identity of this Au20 cluster is confirmed by ESI-MS. The chelation of multidentate phosphines enhances the stability of this Au20 cluster.

Au19 Nanocluster Featuring a V-Shaped Alkynyl–Gold Motif

A novel Au19 nanocluster with a composition of [Au19(PhC≡C)9(Hdppa)3](SbF6)2 was synthesized (Hdppa = N,N-bis(diphenylphosphino)amine). Single crystal X-ray structural analysis reveals that the cluster comprises a centered icosahedral Au13 core hugged by three V-shaped PhC≡C-Au-C≡C(Ph)-Au-C≡CPh motifs. Such motif is observed for the first time in an alkynyl-protected gold nanocluster. The Au19 cluster shows two main optical-absorption bands at 1.25 and 2.25 eV, confirmed by time-dependent density functional theory. Orbital analysis indicates that PhC≡C- groups can actively participate in the frontier orbitals of the whole cluster. The new Au19 cluster and the novel alkynyl-gold motif open the door to understanding the alkynyl-gold interface and discovering many potential members of this new class of gold clusters.

[Ag(70)(PW(9)O(34))(2)((t)BuC[triple bond, length as m-dash]C)(44)(H(2)O)(2)](8+): ionothermal synthesis of a silver cluster encapsulating lacunary polyoxometalate ions.

A silver alkynyl cluster containing a Ag70 shell and two lacunary [PW9O34](9-) templating ions was synthesized by an ionothermal approach. Fast core-shell electronic communication between silver(i) centers and polyoxometalates was verified via cyclic voltammetry studies in [BMIm]BF4.

Alkynyl‐Protected Au23 Nanocluster: A 12‐Electron System

A 23-gold-atom nanocluster was prepared by NaBH4-mediated reduction of a solution of PhC≡CAu and Ph3PAuSbF6 in CH2Cl2. The cluster composition was determined to be [Au23(PhC≡C)9(Ph3P)6](2+) and single-crystal X-ray diffraction revealed that the cluster has an unprecedented Au17 kernel protected by three PhC2-Au-C2 (Ph)-Au-C2 Ph motifs and six Ph3P groups. The Au17 core can be viewed as the fusion of two Au10 units sharing a Au3 triangle. Electronic structure analysis from DFT calculations suggests that the stability of this unusual 12-electron cluster is a result of the splitting of the superatomic 1D orbitals under D3h symmetry of the Au17 kernel. The discovery and determination of the structure of the Au23 cluster demonstrates the versatility of the alkynyl ligand in leading to the formation of new cluster compounds.

Chloride-Promoted Formation of a Bimetallic Nanocluster Au80Ag30 and the Total Structure Determination

We report the total structure determination of a large bimetallic nanocluster with an overall composition of [Au80Ag30(C≡CPh)42Cl9]Cl. It is the largest structurally characterized bimetallic coinage nanocluster so far. The 110 metal atoms are distributed in a concentric four-shell Russian doll arrangement, Au6@Au35@Ag30Au18@Au21. There are 42 PhC≡C- ligands and 9 μ2-chloride ligands clamping on the cluster surface. The chloride is proven to be critical for the formation of this giant cluster, as the control experiment in the absence of halide gives only smaller species. This work demonstrates that the halide can play a key role in the formation of a large metal nanocluster, and the halide effect should be considered in the design and synthesis of metal nanoclusters.

Geminal tetraauration of acetonitrile: hemilabile-phosphine-stabilized Au8Ag4 cluster compounds.

Unprecedented geminal tetraauration of acetonitrile has been realized through C-H activation by Au(I)-Ag(I) clusters under mild conditions. The reaction of [OAu3Ag(dppy)3](BF4)2 (dppy = diphenylphosphino-2-pyridine) (1), AgBF4, and acetonitrile in the presence of methanol at room temperature resulted in the isolation of the novel cluster [(CCN)2Au8Ag4(dppy)8(CH3CN)2](BF4)6 (2). The centrosymmetric structure consists of two Au4Ag2 motifs stabilized by hemilabile phosphines. Triply deprotonated acetonitrile (CCN(3-)) is found in a Au4Ag environment with the terminal carbon bridging four Au(I) centers and the nitrogen donor linking a Ag(I) ion, which is the first example of a μ5-CCN(3-) coordination mode. A concerted metalation/deprotonation process for the C-H activation of acetonitrile that indicates the importance of the oxo ion of the oxonium Au(I) cluster is proposed. Cluster 2 emits bright green light in the solid state at room temperature upon UV irradiation.

Methanol triggered ligand flip isomerization in a binuclear copper(I) complex and the luminescence response

Methanol drives the blue emissive complex, [Cu(2)(dppy)(3)(MeCN)](BF(4))(2) (dppy = diphenylphosphino-pyridine), with a head-to-tail arrangement of the three bridging phosphine ligands to convert to its linkage isomer (head-to-head, green emissive) in the solid state, and the transformation could be reversibly realized through recrystallization in different solvents.

A luminescent gold(I)-copper(I) cluster with unprecedented carbon-centered trigonal prismatic hexagold.

An unprecedented trigonal prismatic (μ(6)-C)Au(6) structure has been found in a novel gold(I)-copper(I) cluster with a hypercoordinated carbon, [CAu(6)Cu(2)(dppy)(6)](BF(4))(4); the incorporation of copper ions enhances the rigidity and integrity of the cluster and turns on the bright red solution luminescence.

Postclustering Dynamic Covalent Modification for Chirality Control and Chiral Sensing

Cluster-based functional materials are appealing, because clusters are well-defined building units that can be rationally incorporated for the tuning of structures and properties. Postclustering modification (PCM) allows for tailoring properties through the structural modification of a cluster with preorganized funtional groups. By introducing aldehydes into a robust gold-silver cluster via a protection-deprotection process, we manage to synthesize a new cluster bearing six reactive sites, which are available for PCM through dynamic covalent imine bonds formation with chiral monoamines. Chirality is transferred from the amine to the gold-silver cluster. The homochirality of the resulted cluster has been confirmed by X-ray structural determination and CD spetroscopy. Intense CD signals make it practical for chiral recognition and ee value determination of chiral monoamines. The strategy of prefunctionalizing of cluster and the concept of PCM open a broader prospect for cluster design and applications.