The rational design of binuclear Au(I)–Au(I), Au(II)–Au(II), and Au(I)–Au(III) complexes requires an understanding of how the redox states interconvert. Herein, the electrochemical ...interconversion of the three oxidation states I, II, and III is reported on the voltammetric (cyclic and rotating disk electrode) time scales for binuclear gold complexes containing C6F4PPh2 as a ligand, to demonstrate for the first time formation of a binuclear Au(II)–Au(II) from a Au(I)–Au(III) complex. Results are supported by bulk electrolysis and coulometry with reaction products being identified by 31P NMR and UV–vis spectroscopy. All electrochemical processes involve an overall two-electron charge-transfer process with no one-electron intermediate being detected. Importantly, the kinetically rather than thermodynamically favored isomer Au2 IIX2(μ-2-C6F4PPh2)2 is formed on redox cycling of XAuI(μ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuIIIX (X = Cl, ONO2). Finally, a mechanism is proposed to explain the simultaneous change of coordination of the chelating carbanionic ligand to bridging mode and interconversion of oxidation states in binuclear gold complexes.
Monometallic (Ag, Au, Pd), bimetallic (AgAu, AuPd) and trimetallic (Ag-Au-Pd) nanostructures, were generated using dextran as a natural polymer. The simultaneous co-reduction of multiple metal ...precursors with dextran gave a fine control to produce spherical shape Ag-Au-Pd trimetallic nanostructures. Small-sized Ag monometallic nanostructures of 8.7 nm were enlarged to 15.7 nm for AgAu bimetallic nanostructures. While, trimetallic nanostructures from Ag-Au-Pd was produced with much smaller size of 3.8 nm and quite narrower size distribution of 2–7 nm. The spectral analysis confirmed that the alcoholic groups of dextran were responsible for the reduction of metal ions to produce nanostructures and consequently oxidized to aldehydic/ketonic groups. The catalytic performance of the synthesized nanostructures was evaluated for the reduction of p-nitroaniline and the results demonstrated that there was a strong correlation between catalytic activity and composition of nanostructures. Half time of the reduction was diminished from 3.93 to 0.90 min. for Pd monometallic and Ag-Au-Pd trimetallic nanostructures, respectively. Using of the trimetallic nanostructure as a catalyst results in acceleration the reduction reaction 151 times. The results showed a promising approach to boost catalytic activities of the trimetallic nanostructures which were prepared via quite simple green method at ambient conditions.
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•Fabrication of monometallic, bimetallic, and trimetallic nanostructures by using dextran was presented.•AgNPs, Ag-AuNPs and Ag-Au-PdNPs were produced with 8.7, 15.7, and 3.8 nm, respectively.•Dextran alcoholic groups reduced metal ions to metallic nanostructures.•Trimetallic nanostructure as a catalyst accelerated the reduction of p-nitroaniline by 151 times.•The half time of reduction reaction was diminished from 3.93 min. for PdNPs to 0.90 min. for Ag-Au-PdNPs.
In this paper, Au@Ag nanopencil is designed as a multimodality plasmonic nanoprobe based on asymmetric etching for the detection of SCN
and ClO
. Au@Ag nanopencil with Au tip and Au@Ag rod is ...prepared by asymmetric tailoring of uniformly grown silver-covered gold nanopyramids under the combined effect of partial galvanic replacement and redox reaction. By asymmetric etching in different systems, Au@Ag nanopencil exhibits diversified changes in the plasmonic absorption band: O
facilitated by SCN
etches Au@Ag rod from the end to the tip, causing a blue shift of the localized surface plasmon resonance (LSPR) peak as the aspect ratio decreases; while the ClO
can retain Au@Ag shell and etch Ag within rod from the tip to the end, causing a redshift of the LSPR peak as the coupling resonance weakens. Based on peak shifts in different directions, a multimodality detection of SCN
and ClO
has been established. The results demonstrate the detection limits of SCN
and ClO
are 160 and 6.7 nm, and the linear ranges are 1-600 µm and 0.05-13 µm, respectively. The finely designed Au@Ag nanopencil not only broadens the horizon of designing heterogeneous structures, but also enriches the strategy of constructing multimodality sensing platform.
Metal-metal bonding interactions have been used to generate a number of unique supramolecular assemblies with fascinating functions. We presented here a new class of gold(I)-containing ...metallosupramolecular cages and cage-built two-dimensional (2-D) arrays of {Au8L2}n (n = 1 or ∞, L = tetrakis-dithiocarbamato-calix4arene, TDCC), 1-3, which are constructed from the self-assembly of deep-cavitand calix4arene-based supramolecular cages consisting of octanuclear Au(I) motifs. Synchrotron radiation X-ray diffraction structural analyses of 1-3 revealed their quadruple-stranded helicate dimeric cage structure and the presence of 2-D arrays of cages linked together by inter- and intramolecular Au(I)···Au(I) interactions. Electronic absorption and emission studies of complexes 1-3 indicated the occurrence of a programmable self-assembly process in a concentration-dependent stepwise manner with the links built via aurophilic interactions. These novel gold(I) supramolecular cages exhibited green phosphorescence and have been shown to serve as highly selective proof-of-concept luminescent sensors toward Ag(I) cation among various competitive transition-metal ions.
New dinuclear Au(I), Au(II) and Au(III) complexes containing (CF2)n bridging chains were obtained. Metallomacrocycles Au2{μ‐(CF2)4}{μ‐diphosphine} show an uncommon figure‐eight structure, the ...helicity inversion barrier of which is influenced by aurophilic interactions and steric constraints imposed by the diphosphine. Halogenation of LAu(CF2)4AuL (L=PPh3, PMe3, (dppf)1/2, (binap)1/2) gave Au(II)2 species, some of which display unprecedented folded structures with Au−Au bonds. Aurophilic interactions facilitate this oxidation process by preorganizing the starting Au(I)2 complexes and lowering its redox potential. The obtained Au(II)2 complexes undergo thermal or photochemical elimination of R3PAuX to give Au(III) perfluorinated auracycles. Evidence of a radical mechanism for these decomposition reactions was obtained.
Aurophilic interactions promote the oxidation of AuI2 compounds to give complexes containing a AuII‐AuII bond instead of AuIII2 or mixed‐valent species. The obtained AuII complexes undergo thermal or photochemical elimination of R3PAuX to give AuIII perfluorinated auracyclic complexes through radical intermediates.
A (MeDalphos)AuCl complex was found to efficiently catalyze the cross-coupling of indoles and allyl acetates/alcohols. The reaction tolerates many functional groups and selectively affords the ...branched C3-allylated products from both α- and γ-substituted allyl substrates. It takes the advantage of the hemilabile character of the P∧N ligand. The C(sp2)–C(sp3) coupling operates via a Au(I)/Au(III) redox cycle and involves a dicationic π-allyl Au(III) complex as a key intermediate. In this case, the allyl moiety adopts an asymmetric σ + π-coordination mode, as substantiated by NMR spectroscopy and density functional theory (DFT) calculations.
A fundamental understanding of the luminescence of Au–thiolate nanoclusters (NCs), such as the origin of emission and the size effect in luminescence, is pivotal to the development of efficient ...synthesis routes for highly luminescent Au NCs. This paper reports an interesting finding of Au(I)–thiolate complexes: strong luminescence emission by the mechanism of aggregation-induced emission (AIE). The AIE property of the complexes was then used to develop a simple one-pot synthesis of highly luminescent Au–thiolate NCs with a quantum yield of ∼15%. Our key strategy was to induce the controlled aggregation of Au(I)–thiolate complexes on in situ generated Au(0) cores to form Au(0)@Au(I)–thiolate core–shell NCs where strong luminescence was generated by the AIE of Au(I)–thiolate complexes on the NC surface. We were able to extend the synthetic strategy to other thiolate ligands with added functionalities (in the form of custom-designed peptides). The discovery (e.g., identifying the source of emission and the size effect in luminescence) and the synthesis protocols in this study can contribute significantly to better understanding of these new luminescence probes and the development of new synthetic routes.
The Λ (Λ¯) hyperon polarization along the beam direction has been measured in Au+Au collisions at sNN=200 GeV, for the first time in heavy-ion collisions. The polarization dependence on the ...hyperons' emission angle relative to the elliptic flow plane exhibits a second harmonic sine modulation, indicating a quadrupole pattern of the vorticity component along the beam direction, expected due to elliptic flow. The polarization is found to increase in more peripheral collisions, and shows no strong transverse momentum (pT) dependence at pT greater than 1 GeV/c. The magnitude of the signal is about 5 times smaller than those predicted by hydrodynamic and multiphase transport models; the observed phase of the emission angle dependence is also opposite to these model predictions. In contrast, the kinematic vorticity calculations in the blast-wave model tuned to reproduce particle spectra, elliptic flow, and the azimuthal dependence of the Gaussian source radii measured with the Hanbury Brown–Twiss intensity interferometry technique reproduce well the modulation phase measured in the data and capture the centrality and transverse momentum dependence of the polarization signal.
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