Small Gold(I) and Gold(I)–Silver(I) Clusters by C−Si Auration

Auration of o-trimethylsilyl arylphosphines leads to the formation of gold and gold–silver clusters with ortho-metalated phosphines displaying 3c–2e Au−C−M bonds (M=Au/Ag). Hexagold clusters [Au₆L₄](X)₂ are obtained by reaction of (L−TMS)AuCl with AgX, whereas reaction with AgX and Ag₂O leads to gold–silver clusters [Au₄Ag₂L₄](X)₂. Oxo-trigold(I) species [Au₃O]⁺ were identified as the intermediates in the formation of the silver-doped clusters. Other [Au₅], [Au₄Ag], and [Au₁₂Ag₄] clusters were also obtained. Clusters containing PAu−Au−AuP structural motif display good catalytic activity in the activation of alkynes under homogeneous conditions.     

Unraveling the Impact of Gold(I)–Thiolate Motifs on the Aggregation-Induced Emission of Gold Nanoclusters

Aggregation-induced emission (AIE) provides an efficient strategy to synthesize highly luminescent metal nanoclusters (NCs), however, rational control of emission energy and intensity of metal NCs is still challenging. This communication reveals the impact of surface Au^I-thiolate motifs on the AIE properties of Au NCs, by employing a series of water-soluble glutathione (GSH)-coordinated Au complexes and NCs as a model ([Au₁₀SR₁₀], [Au₁₅SR₁₃], [Au₁₈SR₁₄], and [Au₂₅SR₁₈]⁻, SR=thiolate ligand). Spectroscopic investigations show that the emission wavelength of Au NCs is adjustable from visible to the near-infrared II (NIR-II) region by controlling the length of the Au^I-SR motifs on the NC surface. Decreasing the length of Au^I-SR motifs also changes the origin of cluster luminescence from AIE-type phosphorescence to Au⁰-core-dictated fluorescence. This effect becomes more prominent when the degree of aggregation of Au NCs increases in solution.     

On Gold(I) Complexes and Anodic Gold Dissolution in Sulfite–Thiourea Solutions

Processes involving gold(I) complexes were studied in sulfite–thiourea (TU) solutions. It is shown that at pH >5 the complex [\( {\text{AuTU}}_{2}^{ + } \)] undergoes irreversible decomposition followed by deprotonation and formation of a solid phase. From the data of pH in mixed solutions, the equilibrium constants were evaluated: \( {\text{Au}}({\text{SO}}_{3} )_{2}^{3 - } + i{\text{TU}} \rightleftharpoons {\text{Au}}({\text{SO}}_{3} )_{2 - i} {\text{TU}}_{i}^{2i - 3} + i{\text{SO}}_{3}^{2 - } \), log₁₀ β ₁ = ?1.2, log₁₀ β ₂ = ?3.6. Some aspects of the anodic dissolution of gold in mixed sulfite–thiourea solutions are considered. With the help of the carbonate buffer system the change of the anodic current density j _a was studied at high pH; j _a (pH) has a maximum at pH 11.6–11.9 for E _a = 0.3–0.6 V (vs. NHE). At pH > 12.0, the j _a values decrease sharply. Possible mechanisms of anodic gold dissolution, as well as the role of sulfite, are discussed.     

Gold(I)/Gold(III) Catalysis that Merges Oxidative Addition and π-Alkene Activation

Heteroarylation of alkenes with aryl iodides was efficiently achieved with a (MeDalphos)AuCl complex through Au^I/Au^III catalysis. The possibility to combine oxidative addition of aryl iodides and π-activation of alkenes at gold is demonstrated for the first time. The reaction is robust and general (>30 examples including internal alkenes, 5-, 6-, and 7-membered rings). It is regioselective and leads exclusively to trans addition products. The (P,N) gold complex is most efficient with electron-rich aryl substrates, which are troublesome with alternative photoredox/oxidative approaches. In addition, it provides a very unusual switch in regioselectivity from 5-exo to 6-endo cyclization between the Z and E isomers of internal alkenols.     

Simultaneous Determination of Gold(Ⅲ) and Copper(Ⅱ) with Two-Way Stripping Voltammetry

The simultaneous determination of Au(Ⅲ) and Cu(Ⅱ) by atomic absorption spectrometry^[1,2], X-ray fluorescence^[3] and differential-pulse polarography^[4] have been reported. The apparatus used in spectrochemical analysis are complex and expensive. The method reported in reference^[4] involves a poisonous electrode-DME(dropping-mercury electrode) and unsatisfied performance with the detection limit. We had reported the determination of trace Au(Ⅲ) or Cu(Ⅱ) by a sensitive tripping voltammetry with solid electrode^[5], but there is no report about the simultaneous determination of trace Au(Ⅲ) and Cu(Ⅱ) by stripping voltammetry ever since.     

Gold(III) π-Allyl Complexes

Gold(III) π-complexes have been authenticated recently with alkenes, alkynes, and arenes. The key importance of Pd^II π-allyl complexes in organometallic chemistry (Tsuji–Trost reaction) prompted us to explore gold(III) π-allyl complexes, which have remained elusive so far. The (P,C)Au^III(allyl) and (methallyl) complexes 3 and 3′ were readily prepared and isolated as thermally and air-stable solids. Spectroscopic and crystallographic analyses combined with detailed DFT calculations support tight quasi-symmetric η³-coordination of the allyl moiety. The π-allyl gold(III) complexes are activated towards nucleophilic additions, as substantiated with β-diketo enolates.     

Gold(I)-diphenylphosphinomethane–arylazoimidazole: synthesis and multinuclear NMR investigation

Reaction of [Au₂(dppm)Cl₂] with AgOTf in CH₂Cl₂ medium followed ligand addition and leads to [Au₂(dppm)(RaaiR′)](OTf) [RaaiR′ = p-R–C₆H₄–N = N–C₃H₂–NN–1–R′, (1–3), abbreviated as N,N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1), CH₂CH₃ (2), CH₂Ph (3), OSO₂CF₃ is the triflate anion, and dppm is the diphenylphosphinomethane-ring]. The ¹H-n.m.r. spectral measurements suggest methylene, –CH₂–, in RaaiEt gives a complex AB type multiplet while in RaaiCH₂Ph it shows AB type quartets with coupling constant of avg. 6 Hz. Considering all the moities there are a lot of different carbon atoms in the molecule which gives a lot of different peaks in the ¹³C-n.m.r spectrum. In the ¹H–¹H-COSY spectrum of the present complexes and contour peaks in the ¹H–¹³C-HMQC spectrum in the present complexes, assign the solution structure and stereoretentive transformation in each step.     

Porphyrins and Metalloporphyrins Combined with N-Heterocyclic Carbene (NHC) Gold(I) Complexes for Photodynamic Therapy Application: What Is the Weight of the Heavy Atom Effect?

The photophysical properties of two classes of porphyrins and metalloporphyrins linked to N-heterocyclic carbene (NHC) Au(I) complexes have been investigated by means of density functional theory and its time-dependent extension for their potential application in photodynamic therapy. For this purpose, the absorption spectra, the singlet–triplet energy gaps, and the spin–orbit coupling (SOC) constants have been determined. The obtained results show that all the studied compounds possess the appropriate properties to generate cytotoxic singlet molecular oxygen, and consequently, they can be employed as photosensitizers in photodynamic therapy. Nevertheless, on the basis of the computed SOCs and the analysis of the metal contribution to the involved molecular orbitals, a different influence in terms of the heavy atom effect in promoting the intersystem crossing process has been found as a function of the identity of the metal center and its position in the center of the porphyrin core or linked to the peripheral NHC.     

Kinetics and mechanism of the anation of (αβ)-hydroxo(tetraethylenepentamine)cobalt(III) by thiosulfate, the base hydrolysis of the (sulfur-bonded) thiosulfato(tetraethylenepentamine)-cobalt(III) and photochemistry of oxygen and sulfur-bonded thiosulfato complexes

Summary The reaction of ()-(tetren)CoOH²⁺ with S₂O ₃ ^2- in the 7.25–8.28 pH range at 20–40 °C yielded S- (yellow) and O- (purple) bonded thiosulfato(tetren)cobalt(III) complexes, the former in larger quantities. The rate determining step is preceded by diffusion-controlled ion-pair [(tetren)CoOH²⁺,S₂O ₃ ^2- ] formation. Replacement of coordinated OH^- by S₂O ₃ ^2- is interpreted in terms of an internal conjugate base mechanism: (tetren)CoOH²⁺ (tetren-H)CoOH ₂ ²⁺ , the reactive amido conjugate base being generated by intramolecular proton transfer from the coordinated NH site.In acid medium the S-bonded (tetren)Co(S₂O₃)⁺ is highly stable to redox decomposition, in contrast to its pentaammine analogue. The complex however, undergoes base hydrolysis yielding the corresponding hydroxo complex. The rate and activation parameters for the base hydrolysis have been reported. Photolysis of O- and S-bonded isomers of [(tetren)CoS₂O₃]⁺ in acidic medium at 254 and 313 nm, respectively, yielded aquation products accompanied by some decomposition of S₂O ₃ ^2- .     

Ab Initio Molecular Orbital Calculation on Dinuclear Gold(Ⅰ)Complexes──Metal-Metal Interaction and Electronic Structure of Binuclear Gold(Ⅰ)Complexes with Bridging Bidentate Ligands

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Full Protection of Intensely Luminescent Gold(I)–Silver(I) Cluster by Phosphine Ligands and Inorganic Anions

An intensely luminescent gold(I)–silver(I) cluster [(C)(AuPPhpy₂)₆Ag₆(CF₃CO₂)₃](BF₄)₅ (PPhpy₂=bis(2-pyridyl)phenylphosphine) ( 3 ) is synthesized by the reaction of [(C)(AuPPhpy₂)₆Ag₄](BF₄)₆ with AgCF₃CO₂. All eight faces of the octahedral C@Au₆ core in 3 are capped, that is, six faces are capped by silver ions and two by tetrafluoroborates. Cluster 3 is intensely luminescent in solution with a quantum yield of 92 %. Ligation of CF₃CO₂⁻ ions is vital for the construction and emission properties of 3 , as confirmed by DFT calculations. BF₄⁻ ions are involved in the protecting sphere of the metal core, as evidenced by ¹⁹F NMR data. The participation of phosphines, CF₃CO₂⁻, and BF₄⁻ ions in the protection of the emissive core and the enhancement of the rigidity of the cluster result in the high emission efficiency. This is the first example of organic ligands and inorganic anions forming a rigid protecting sphere for luminescent coinage-metal clusters.     

Gold(III)–pyrrolidinedithiocarbamato Derivatives as Antineoplastic Agents

Transition metals offer many possibilities in developing potent chemotherapeutic agents. They are endowed with a variety of oxidation states, allowing for the selection of their coordination numbers and geometries via the choice of proper ligands, leading to the tuning of their final biological properties. We report here on the synthesis, physico-chemical characterization, and solution behavior of two gold(III) pyrrolidinedithiocarbamates (PDT), namely [Au^IIIBr₂(PDT)] and [Au^IIICl₂(PDT)]. We found that the bromide derivative was more effective than the chloride one in inducing cell death for several cancer cell lines. [Au^IIIBr₂(PDT)] elicited oxidative stress with effects on the permeability transition pore, a mitochondrial channel whose opening leads to cell death. More efficient antineoplastic strategies are required for the widespread burden that is cancer. In line with this, our results indicate that [Au^IIIBr₂(PDT)] is a promising antineoplastic agent that targets cellular components with crucial functions for the survival of tumor cells.     

Synthesis of the Natural Products Resveratrol (Ⅰ) and Isorhapotogenin (Ⅱ)

ResveratrolIandisorhapotigeninIIaretwonaturalproductswithmanybiologicalactivities',andtheirtotalsynthesis'havebeenreported.LinMaoetal3flrstisolatedthemfromG.parvofOlium,atraditionalChineseherbusedtotreatrheumatoidarthritis,ulcerbleedingandbronchitis.Inanattempttopreparecnoughsamplesfortlirtherpharmacologicalevaluation,severalsynthesisstrategieshavebeenexplored'.WchavcdevelopedtwosyntheticapproachesofIandIIinSchemelandScheme2,respectivcly.Startingfrom3,5-dihydroxybenzoicacid,thecompound2wa…     

Structure and Luminescence Property of a Linear Tetranuclear Gold(Ⅰ)-thiolate Complex through Au-Au Interaction

The synthesis,structure and luminescent property of a tetranuclear gold(Ⅰ)complex with doubly bridging diethyldithiocarbamate(Et2dtc)and 1,1-bis(diphenylphosphino)ethene((Ph2P)2C=CH2)are described.The complex crystallizes in monoclinic space group C2/c with a=26.785(7),b=25.654(6),c=12.277(3)A,β=106.879(5)°,V=8073(4)A~3,Z=8,C31H32Au2F6NO3P2S2Sb,Mr=1222.32,Dc=2.011 g/cm~3,F(000)=4592,Rint=0.0529,T=293(2)K,μ=8.157 mm~(-1),the final R=0.0464 and wR=0.1444 for 5804 observed reflections with I2σ(Ⅰ).The intramolecular and intermolecular Au¨Au distances are 2.8670(9)and 3.2367(9)A,respectively.Weak emission appears at 517 nm at room temperature in the solid state.     

Synthesis of(±)-Deoxyschisandrin and the Corresponding Trans-lsomer

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New Intermetalloid Ge9-clusters with Copper and Gold: Filling Vacancies in the Cluster Chemistry of [Ge9(Hyp)3]− (Hyp=Si(SiMe3)3)

We present a series of new intermetalloid clusters (R₃P)CuGe₉₍(Hyp)₃, (R=Me, Et, iPr, nBu, tBu) (Hyp=Si(SiMe₃)₃) (R₃P)AuGe₉(Hyp)₃MGe₉(Hyp)₃ (R=Ph, Me; M=Au, Cu). In conjunction with already known clusters, these give new insights into the bonding situation of metal bridged Ge₉ clusters as well as a better understanding of the formation of these clusters. Additionally, the intermetalloid clusters with the smallest phosphine PMe₃ show new bonding motives.     

Crystal Growth and Crystal Structures of Gold(V) Compounds: Cu(AuF6)2, Ag(AuF6)2, and O2(CuF)3(AuF6)4 ⋅ HF

Crystal growth from anhydrous hydrogen fluoride solutions of M²⁺ (M=Cu, Ag) and [AuF₆]⁻ gave M(AuF₆)₂ salts (M=Cu, Ag). Similar attempts to prepare single crystals of the corresponding nickel, zinc and magnesium salts failed. The crystal structure of Cu(AuF₆)₂ consists of layers of Cu²⁺ cations connected by [AuF₆]⁻ anions, thus forming slabs. Only van der Waals interactions exist between adjacent slabs. The crystal structure of Ag(AuF₆)₂ consists of a three-dimensional framework in which Ag⁺ cations are linked by [AuF₆]⁻ anions. Both structures are members of the M^II(X^VF₆)₂ family, in which seven different structure types have been observed to date. In the crystal structure of O₂(CuF)₃(AuF₆)₄ ⋅ HF, the bridging AuF₆ units connect [−Cu−F−Cu−F−]_∞ chains to form stacks between which O₂⁺ cations and HF molecules are located.     

Steric,Electronic and Conformational Synergistic Effects in the Gold(I)-catalyzed α-C−H Bond Functionalization of Tertiary Amines**

Direct C−H bond functionalization is a useful strategy for the straightforward formation of C−C and C−Heteroatom bonds. In the present work, a unique approach for the challenging electrophilic Au-catalyzed α-C−H bond functionalization of tertiary amines is presented. Electronic, steric and conformational synergistic effects exerted by the use of a malonate unit in the substrate were key to the success of this transformation. This new reactivity was applied to the synthesis of tetrahydro-γ-carboline products which, under oxidative conditions, could be converted into valuable structural motifs found in bioactive alkaloid natural products.     

The Molecular Recognition Characteristics of ω-MercaptoMethoxy Poly(Ethylene Glycol) Self-assembled Monolayer at Gold Electrode and the Detection of Dopamine in Serum

Recently,theselfassembledmonolayersofto-mercaPtocarboxylicacidongoldelectrodeswereusedasameanstodetectDAinthepresenceofAA.l-2DAhasagoodresponseatthenegativelychargedSAMselectrodebutAAhaslittleresponseonit.InthespaPer,wehaveaPpliedto-mercaPtomethoxypoly(ethyleneglycol)(MPEG)ongoldelectrodesurfacetoformselfassembledmonolayerswithmolecularrecognitionproperty.DAhadgoodresponseatthiselectrode.However,AAwasrepelledfromtheMPEGfilm.ThsfilmelectrodecanbeusedtodetectDAintliepresenceofhighcon…     

Steric,Electronic and Conformational Synergistic Effects in the Gold(I)-catalyzed α-C−H Bond Functionalization of Tertiary Amines**

Direct C−H bond functionalization is a useful strategy for the straightforward formation of C−C and C−Heteroatom bonds. In the present work, a unique approach for the challenging electrophilic Au-catalyzed α-C−H bond functionalization of tertiary amines is presented. Electronic, steric and conformational synergistic effects exerted by the use of a malonate unit in the substrate were key to the success of this transformation. This new reactivity was applied to the synthesis of tetrahydro-γ-carboline products which, under oxidative conditions, could be converted into valuable structural motifs found in bioactive alkaloid natural products.