用第一原理理解与预测巯基金纳米簇

This is an exciting time for studying thiolated gold nanoclusters.Single crystal structures of Au102(SR)44 and Au25(SR) 1-8 (—SR being an organothiolate group) bring both surprises and excitement in this field.First principles density functional theory (DFT) simulations turn out to be an important tool to understand and predict thiolated gold nanoclusters.In this review,I summarize the progresses made by us and others in applying first principles DFT to thiolated gold nanoclusters,as inspired by the recent ...     

Fcc versus Non‐fcc Structural Isomerism of Gold Nanoparticles with Kernel Atom Packing Dependent Photoluminescence

Structural isomerism allows the correlation between structures and properties to be investigated. Unfortunately, the structural isomers of metal nanoparticles are rare and genuine structural isomerism with distinctly different kernel atom packing (e.g., face‐centered cubic (fcc) vs. non‐fcc) has not been reported until now. Herein we introduce a novel ion‐induction method to synthesize a unique gold nanocluster with a twist mirror symmetry structure. The as‐synthesized nanocluster has the same composition but different kernel atom packing to an existing gold nanocluster Au₄₂(TBBT)₂₆ (TBBT=4‐tert‐butylbenzenethiolate). The fcc‐structured Au₄₂(TBBT)₂₆ nanocluster shows more enhanced photoluminescence than the non‐fcc‐structured Au₄₂(TBBT)₂₆ nanocluster, indicating that the fcc‐structure is more beneficial for emission than the non‐fcc structure. This idea was supported by comparison of the emission intensity of another three pairs of gold nanoclusters with similar compositions and sizes but with different kernel atom packings (fcc vs. non‐fcc).     

Phosphine-Triggered Structural Defects in Au44 Homologues Boost Electrocatalytic CO2 Reduction

The systematic induction of structural defects at the atomic level is crucial to metal nanocluster research because it endows cluster-based catalysts with highly reactive centers and allows for a comprehensive investigation of viable reaction pathways. Herein, by substituting neutral phosphine ligands for surface anionic thiolate ligands, we establish that one or two Au₃ triangular units can be successfully introduced into the double-stranded helical kernel of Au₄₄(TBBT)₂₈, where TBBT=4-tert-butylbenzenethiolate, resulting in the formation of two atomically precise defective Au₄₄ nanoclusters. Along with the regular face-centered-cubic (fcc) nanocluster, the first series of mixed-ligand cluster homologues is identified, with a unified formula of Au₄₄(PPh₃)_n(TBBT)_28−2n (n=0–2). The Au₄₄(PPh₃)(TBBT)₂₆ nanocluster having major structural defects at the bottom of the fcc lattice demonstrates superior electrocatalytic performance in the CO₂ reduction to CO. Density functional theory calculations indicate that the active site near the defects significantly lowers the free energy for the *COOH formation, the rate-determining step in the whole catalytic process.     

Hard-Sphere Random Close-Packed Au47Cd2(TBBT)31 Nanoclusters with a Faradaic Efficiency of Up to 96 % for Electrocatalytic CO2 Reduction to CO

Metal nanoclusters have recently attracted considerable attention, not only because of their special size range but also because of their well-defined compositions and structures. However, subtly tailoring the compositions and structures of metal nanoclusters for potential applications remains challenging. Now, a two-phase anti-galvanic reduction (AGR) method is presented for precisely tailoring Au₄₄(TBBT)₂₈ to produce Au₄₇Cd₂(TBBT)₃₁ nanoclusters with a hard-sphere random close-packed structure, exhibiting Faradaic efficiencies of up to 96 % at −0.57 V for the electrocatalytic reduction of CO₂ to CO.     

Hard‐Sphere Random Close‐Packed Au47Cd2(TBBT)31 Nanoclusters with a Faradaic Efficiency of Up to 96 % for Electrocatalytic CO2 Reduction to CO

Metal nanoclusters have recently attracted considerable attention, not only because of their special size range but also because of their well‐defined compositions and structures. However, subtly tailoring the compositions and structures of metal nanoclusters for potential applications remains challenging. Now, a two‐phase anti‐galvanic reduction (AGR) method is presented for precisely tailoring Au₄₄(TBBT)₂₈ to produce Au₄₇Cd₂(TBBT)₃₁ nanoclusters with a hard‐sphere random close‐packed structure, exhibiting Faradaic efficiencies of up to 96 % at ?0.57 V for the electrocatalytic reduction of CO₂ to CO.     

Quasi‐Dual‐Packed‐Kerneled Au49(2,4‐DMBT)27 Nanoclusters and the Influence of Kernel Packing on the Electrochemical Gap

Although face‐centered cubic (fcc), body‐centered cubic (bcc), hexagonal close‐packed (hcp), and other structured gold nanoclusters have been reported, it was unclear whether gold nanoclusters with mix‐packed (fcc and non‐fcc) kernels exist, and the correlation between kernel packing and the properties of gold nanoclusters is unknown. A Au₄₉(2,4‐DMBT)₂₇ nanocluster with a shell electron count of 22 has now been been synthesized and structurally resolved by single‐crystal X‐ray crystallography, which revealed that Au₄₉(2,4‐DMBT)₂₇ contains a unique Au₃₄ kernel consisting of one quasi‐fcc‐structured Au₂₁ and one non‐fcc‐structured Au₁₃ unit (where 2,4‐DMBTH=2,4‐dimethylbenzenethiol). Further experiments revealed that the kernel packing greatly influences the electrochemical gap (EG) and the fcc structure has a larger EG than the investigated non‐fcc structure.     

Quantum-sized gold nanoclusters: bridging the gap between organometallics and nanocrystals

This Concept article provides an elementary discussion of a special class of large‐sized gold compounds, so‐called Au nanoclusters, which lies in between traditional organogold compounds (e.g., few‐atom complexes, <1 nm) and face‐centered cubic (fcc) crystalline Au nanoparticles (typically >2 nm). The discussion is focused on the relationship between them, including the evolution from the Au???Au aurophilic interaction in Au^I complexes to the direct Au? Au bond in clusters, and the structural transformation from the fcc structure in nanocrystals to non‐fcc structures in nanoclusters. Thiolate‐protected Au_n(SR)_m nanoclusters are used as a paradigm system. Research on such nanoclusters has achieved considerable advances in recent years and is expected to flourish in the near future, which will bring about exciting progress in both fundamental scientific research and technological applications of nanoclusters of gold and other metals.     

Isomerization-induced enhancement of luminescence in Au28(SR)20 nanoclusters

Understanding the origin and structural basis of the photoluminescence (PL) phenomenon in thiolate-protected metal nanoclusters is of paramount importance for both fundamental science and practical applications. It remains a major challenge to correlate the PL properties with the atomic-level structure due to the complex interplay of the metal core (i.e. the inner kernel) and the exterior shell (i.e. surface Au(i)-thiolate staple motifs). Decoupling these two intertwined structural factors is critical in order to understand the PL origin. Herein, we utilize two Au₂₈(SR)₂₀ nanoclusters with different –R groups, which possess the same core but different shell structures and thus provide an ideal system for the PL study. We discover that the Au₂₈(CHT)₂₀ (CHT: cyclohexanethiolate) nanocluster exhibits a more than 15-fold higher PL quantum yield than the Au₂₈(TBBT)₂₀ nanocluster (TBBT: p-tert-butylbenzenethiolate). Such an enhancement is found to originate from the different structural arrangement of the staple motifs in the shell, which modifies the electron relaxation dynamics in the inner core to different extents for the two nanoclusters. The emergence of a long PL lifetime component in the more emissive Au₂₈(CHT)₂₀ nanocluster reveals that its PL is enhanced by suppressing the nonradiative pathway. The presence of long, interlocked staple motifs is further identified as a key structural parameter that favors the luminescence. Overall, this work offers structural insights into the PL origin in Au₂₈(SR)₂₀ nanoclusters and provides some guidelines for designing luminescent metal nanoclusters for sensing and optoelectronic applications.

Two Au₂₈(SR)₂₀ nanoclusters with an identical core but different shells exhibit a ∼15-fold difference in photoluminescence.     

Homoleptic Alkynyl‐Protected Gold Nanoclusters: Au44(PhC≡C)28 and Au36(PhC≡C)24

For the first time total structure determination of homoleptic alkynyl‐protected gold nanoclusters is reported. The nanoclusters are synthesized by direct reduction of PhC≡CAu, to give Au₄₄(PhC≡C)₂₈ and Au₃₆(PhC≡C)₂₄. The Au₄₄ and Au₃₆ nanoclusters have fcc‐type Au₃₆ and Au₂₈ kernels, respectively, as well as surrounding PhC≡C‐Au‐C₂(Ph)Au‐C≡CPh dimeric “staples” and simple PhC≡C bridges. The structures of Au₄₄(PhC≡C)₂₈ and Au₃₆(PhC≡C)₂₄ are similar to Au₄₄(SR)₂₈ and Au₃₆(SR)₂₄, but the UV/Vis spectra are different. The protecting ligands influence the electronic structures of nanoclusters significantly. The synthesis of these two alkynyl‐protected gold nanoclusters indicates that a series of gold nanoclusters in the general formula Au_x (RC≡C)_y as counterparts to Au_x (SR)_y can be expected.     

Structural evolution of subnano platinum clusters

We present a theoretical study of the structural evolution of small minimum energy platinum clusters, using density functional theory (DFT). Three growth pathways were identified. At the subnanoscale, clusters with triangular packing are energetically most favorable. At a cluster size of approximately n = 19, a structural transition from triangular clusters to icosahedral clusters occurs. A less energetically favorable transition from triangular clusters to fcc‐like clusters takes place at around n = 38. Ionization potentials, electron affinities, and magnetic moments of the triangular clusters were also calculated. Understanding the structures and properties will facilitate studies of the chemical reactivity of Pt nanoclusters toward small molecules. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

An Unprecedented Kernel Growth Mode and Layer-Number-Odevity-Dependent Properties in Gold Nanoclusters

Kernel atoms of Au nanoclusters are packed layer-by-layer along the [001] direction with every full (001) monolayer composed of 8 Au atoms (Au₈ unit) in nanoclusters with formula of Au_8n+4(TBBT)_4n+8 (n is the number of Au₈ units; TBBTH=4-tert-butylbenzenelthiol). It is unclear whether the kernel atoms can be stacked in a defective-layer way along the [001] direction during growth of the series of nanoclusters and how the kernel layer number affects properties. Now, a nanocluster is synthesized that is precisely characterized by mass spectrometry and single-crystal X-ray crystallography, revealing a layer stacking mode in which a half monolayer composed of 4 atoms (Au₄ unit) is stacked on the full monolayer along the [001] direction. The size and the odevity of the kernel layer number influence the properties (polarity, photoluminescence) of gold nanoclusters. The obtained nanocluster extends the previous formula from Au_8n+4(TBBT)_4n+8 to Au_4n+4(TBBT)_2n+8 (n is the number of Au₄ units).     

An Unprecedented Kernel Growth Mode and Layer‐Number‐Odevity‐Dependent Properties in Gold Nanoclusters

Kernel atoms of Au nanoclusters are packed layer‐by‐layer along the [001] direction with every full (001) monolayer composed of 8 Au atoms (Au₈ unit) in nanoclusters with formula of Au_8n+4(TBBT)_4n+8 (n is the number of Au₈ units; TBBTH=4‐tert‐butylbenzenelthiol). It is unclear whether the kernel atoms can be stacked in a defective‐layer way along the [001] direction during growth of the series of nanoclusters and how the kernel layer number affects properties. Now, a nanocluster is synthesized that is precisely characterized by mass spectrometry and single‐crystal X‐ray crystallography, revealing a layer stacking mode in which a half monolayer composed of 4 atoms (Au₄ unit) is stacked on the full monolayer along the [001] direction. The size and the odevity of the kernel layer number influence the properties (polarity, photoluminescence) of gold nanoclusters. The obtained nanocluster extends the previous formula from Au_8n+4(TBBT)_4n+8 to Au_4n+4(TBBT)_2n+8 (n is the number of Au₄ units).     

Au10(TBBT)10: the Begining and the End of Aun(TBBT)m Nanoclusters

Gold(I) thiolate compounds (i.e. Au^I-SR) are important precursors for the synthesis of atomically precise Au_n(SR)_m nanoclusters. However, the nature of the Au^I-SR precursor remains elusive. Here, we report that the Au₁₀(TBBT)₁₀ complex is a universal precursor for the synthesis of Au_n(TBBT)_m nanoclusters (where TBBT=4-tertbutylbenzenethiol/thiolate). Interestingly, the Au₁₀(TBBT)₁₀ complex is also found to be re-generated through extended etching of the Au_n(SR)_m nanoclusters with excess of TBBT thiol and O₂. The formation of well-defined Au₁₀(TBBT)₁₀ complex, instead of polymeric Au^I-SR, is attributed to the bulkiness of the TBBT thiol. Through 1D and 2D NMR characterization, the structure of Au₁₀(TBBT)₁₀ is correlated with the previously reported X-ray structure, which contains two inter-penetrated Au₅(TBBT)₅ rings. The photophysical property of Au₁₀(TBBT)₁₀ complex is further probed by femtosecond transient absorption spectroscopy. The accessibility of the precise Au₁₀(TBBT)₁₀ precursor improves the efficiency of the synthesis of the Au_n(TBBT)_m nanoclusters and is expected to further facilitate excellent control and understanding of the reaction mechanisms of nanocluster synthesis.     

Interlocked catenane-like structure predicted in Au24(SR)20: implication to structural evolution of thiolated gold clusters from homoleptic gold(I) thiolates to core-stacked nanoparticles

Atomic structure of a recently synthesized ligand-covered cluster Au(24)(SR)(20) [J. Phys. Chem. Lett., 2010, 1, 1003] is resolved based on the developed classical force-field based divide-and-protect approach. The computed UV-vis absorption spectrum and powder X-ray diffraction (XRD) curve for the lowest-energy isomer are in good agreement with experimental measurements. Unique catenane-like staple motifs are predicted for the first time in core-stacked thiolate-group (RS-) covered gold nanoparticles (RS-AuNPs), suggesting the onset of structural transformation in RS-AuNPs at relatively low Au/SR ratio. Since the lowest-energy structure of Au(24)(SR)(20) entails interlocked Au(5)(SR)(4) and Au(7)(SR)(6) oligomers, it supports a recently proposed growth model of RS-AuNPs [J. Phys. Chem. Lett., 2011, 2, 990], that is, Au(n)(SR)(n-1) oligomers are formed during the initial growth of RS-AuNPs. By comparing the Au-core structure of Au(24)(SR)(20) with other structurally resolved RS-AuNPs, we conclude that the tetrahedral Au(4) motif is a prevalent structural unit for small-sized RS-AuNPs with relatively low Au/SR ratio. The structural prediction of Au(24)(SR)(20) offers additional insights into the structural evolution of thiolated gold clusters from homoleptic gold(I) thiolate to core-stacked RS-AuNPs. Specifically, with the increase of interfacial bond length of Au(core)-S in RS-AuNPs, increasingly larger "metallic" Au-core is formed, which results in smaller HOMO-LUMO (or optical) gap. Calculations of electronic structures and UV-vis absorption spectra of Au(24)(SR)(20) and larger RS-AuNPs (up to ~2 nm in size) show that the ligand layer can strongly affect optical absorption behavior of RS-AuNPs.     

Template‐Free Supracolloidal Self‐Assembly of Atomically Precise Gold Nanoclusters: From 2D Colloidal Crystals to Spherical Capsids

We report supracolloidal self‐assembly of atomically precise and strictly monodisperse gold nanoclusters involving p‐mercaptobenzoic acid ligands (Au₁₀₂‐pMBA₄₄) under aqueous conditions into hexagonally packed monolayer‐thick two‐dimensional facetted colloidal crystals (thickness 2.7 nm) and their bending to closed shells leading to spherical capsids (d ca. 200 nm), as controlled by solvent conditions. The 2D colloidal assembly is driven in template‐free manner by the spontaneous patchiness of the pMBA ligands around the Au₁₀₂‐pMBA₄₄ nanoclusters preferably towards equatorial plane, thus promoting inter‐nanocluster hydrogen bonds and high packing to planar sheets. More generally, the findings encourage to explore atomically precise nanoclusters towards highly controlled colloidal self‐assemblies.     

六核钴羰基簇的P(OC_2H_5)_3取代衍生物的合成、表征与结构

用P(OC_2H_5)_3与母体簇Co_6(μ_6-P)(μ-SCH_2CH_2CH_2S)(μ- PSCH_2CH_2CH_2S)(CO)_(12)进行取代反应得到一个二取代产物Co_6(μ_6-P)(μ- SCH_2CH_2CH_2S)(μ-PSCH_2CH_2CH_2S)(μ-CO)(CO)_9[P(OC_2H_5)_2]_2（I）, 同时还得到了两个一取代产物Co_6(μ_6-P)(μ-SCH_2CH_2CH_2S)(μ- PSCH_2CH_2CH_2S)(CO)_(11)[P(OC_2H_5)_3]（II a和II b,II b是II a的一个同 分异构体,其谱学数据与II a不同）。对合成的三个簇合物进行了元素分析、IR、 ~1H NMR、~(31)P NMR和MS谱学表征,对I做了X射线单晶衍射测定,其晶体属于单 斜晶系,P2_1/n空间群,晶胞参数：a = 1.1170(2) nm,b = 2.3554(5) nm,c = 1.7977(4) nm,β = 99.50(3)°,V = 4.6649(17) nm~3,Z = 4,D_c = 1.763 g/cm~3,F(000) = 2488,μ = 24.64 cm~(-1)。X射线晶体结构分析表明,取代 位置发生在簇合物顶端的两个钴原子上。晶体结构用直接法解出,经用全矩阵最小 二乘法对原子参数进行修正,最后的偏离因子为R_1 = 0.0497,wR_2 = 0.1386。     

Structural Modulation of Two Luminescent Bismuth-organic Frameworks by the Mixed-ligand Synthetic Strategy

Hydrothermal reactions of Bi_2O_3 with pyridine-2,6-dicarboxylic acid(2,6-H_2pdc) and trimesic acid(H3btc)/pyromellitic acid(H4pyr) lead to two bismuth-organic frameworks, namely, [Bi(2,6-pdc)(H_2btc)(H_2O)2]n(1) and [Bi_2(2,6-pdc)2(H2pyr)(H_2O)_2]n(2). Compound 1 crystallizes in the space group P2_1/c. The dimeric {Bi_2} units are linked by 2,6-pdc2-ligands to form 1D chains; Compound 2 exhibits a 2D layered structure with 44 network topology by using dimeric {Bi_2} as secondary building units(SBUs). The chains and layers in 1 and 2 are further arranged into 3D supramolecular structures via hydrogen bonding interactions. The compounds emit blue luminescence. Furthermore, the PXRD, TGA, UV-visible and IR spectra were also studied. Compounds 1, 2 represent good examples of using mixed-ligand approach to construct diversity of luminescent bismuth-organic frameworks.     

Kinetic control and thermodynamic selection in the synthesis of atomically precise gold nanoclusters

This work presents a combined approach of kinetic control and thermodynamic selection for the synthesis of monodisperse 19 gold atom nanoclusters protected by thiolate groups. The step of kinetic control allows the formation of a proper size distribution of initial size-mixed Au(n)(SR)(m) nanoclusters following the reduction of a gold precursor. Unlike the synthesis of Au(25)(SR)(18) nanoclusters, which involves rapid reduction of the gold precursor by NaBH(4) followed by size focusing, the synthesis of 19-atom nanoclusters requires slow reduction effected by a weaker reducing agent, borane-tert-butylamine complex. The initially formed mixture of nanoclusters then undergoes size convergence into a monodisperse product by means of a prolonged aging process. The nanocluster formula was determined to be Au(19)(SC(2)H(4)Ph)(13). This work demonstrates the importance of both kinetic control of the initial size distribution of nanoclusters prior to size focusing and subsequent thermodynamic selection of stable nanoclusters as the final product.     

Divide and protect: capping gold nanoclusters with molecular gold-thiolate rings

Density functional theory calculations are used to explore phosphine- and thiolate-protected gold nanoclusters, namely, Au(39)(PH(3))(14)Cl(6) and Au(38)(SCH(3))(24). For Au(38)(SCH(3))(24), a novel structural motif is predicted, consisting of ringlike (AuSCH(3))(4) units protecting a central Au(14) core. The calculated optical spectrum of this species features a large optical gap (about 1.5 eV) and a prominently peaked structure, correlating with experimental findings of "molecular-like spectra" of thiolate-protected 1.1 nm gold nanoparticles. Ligand-ligand interactions and steric effects in the ligand shell are suggested as possible driving forces toward an ordered gold core structure. A novel mechanism for ligand-exchange reactions on gold clusters is proposed.     

Temperature-dependent structuring of Au-Pt bimetallic nanoclusters on a thin film of Al2O3/NiAl(100)

Au-Pt bimetallic nanoclusters on a thin film of Al(2)O(3)/NiAl(100) undergo significant structural evolution on variation of the temperature. Au and Pt deposited sequentially from the vapor onto thin-film Al(2)O(3)/NiAl(100) at 300 K form preferentially bimetallic nanoclusters (diameter ≦ 6.0 nm and height ≦ 0.8 nm) with both Au and Pt coexisting at the cluster surface, despite the order of metal deposition. These bimetallic clusters are structurally ordered, have a fcc phase and grow with their facets either (111) or (001) parallel to the θ-Al(2)O(3)(100) surface. Upon annealing the clusters to 400-500 K, the Au atoms inside the clusters migrate toward the surface, resulting in formation of a structure with a Pt core and an Au shell. Annealing the sample to 500-650 K reorients the bimetallic clusters--all clusters have their (001) facets parallel to the oxide surface--and induces oxidation of Pt. Such annealed bimetallic clusters become encapsulated with the aluminium-oxide materials and a few Au remain on the surface.