- Crystal structure and solution chemistry of the cytotoxic complex 1,2-dichloro(o-phenanthroline)gold(III) chloride
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The crystal structure of the cytotoxic complex 1,2-dichloro(o-phenanthroline)gold(III) chloride ([AuphenCl2]Cl) has been solved through single crystal X-ray diffraction methods. The complex is square planar and exhibits a quite regular geometry. Crystals of the compound belong to the space group P21/n with a = 12.632(5), b = 16.916(3), c = 12.902(6) ?, β = 91.31(3)° and Z = 8. The coordination of the two gold(III) ions in the asymmetric unit is completed by two chloride ions at 2.972(3) and 3.043(3) ?, respectively, forming a distorted square pyramid. The behavior in solution of [AuphenCl2]Cl was further analyzed through 1H NMR spectroscopy. Results point out that the [Au(III)phen]3+ molecular fragment is stable in solution for several hours, even under physiological conditions, whereas the two chloride ligands are released within approximately 30 min after dissolution in the buffer, at 25°C. The gold(III) chromophore is easily and quickly reduced by addition of stoichiometric amounts of sodium ascorbate; metallic gold is formed and free phenanthroline liberates. The implications of these findings for the biological properties of the [Au(III)phen]3+ species are discussed.
- Abbate,Orioli,Bruni,Marcon,Messori
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- Catalytic activities and properties of Au(III)/Schiff-base complexes in methanol oxidative carbonylation
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Several Au(III)/Schiff-base complexes were studied and proven to be effective catalysts for oxidative carbonylation of methanol to generate dimethyl carbonate (DMC). Effects of Schiff-base ligands, promoters, and promoter mole ratio to Au(III)/Schiff-base complexes on catalytic activity were studied. When the reaction was carried out at a methanol/Au(III) molar ratio of 5060:1, an [AuCl2(phen)]Cl/KI (phen = 1,10-phenanthroline) ratio of 1:4, a CO/O2 pressure of 2:1, and a temperature of 120 °C for 3 h, the conversion, selectivity, and TOF value of the model reaction were 10.8%, 98%, and 138.9 h-1, respectively. The catalyst was characterized by FTIR, UV-vis, 1H NMR, and cyclic voltammetry. The oxidation state of gold during the reaction and the role of KI were discussed using data on electrochemical experiments and ESI-MS. [AuI2(phen)]+ was considered an intermediate in the reaction. A plausible Au(III)/Au(I) catalytic cycle mechanism was proposed.
- Li, Jinjin,Hu, Jianglin,Gu, Yanlong,Mei, Fuming,Li, Tao,Li, Guangxing
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- A molecular-regulation strategy towards low-voltage driven, multi degree of freedom IPMC catheters
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A multi degree of freedom ionic polymer-metal composite (IPMC) active catheter with controllable bending ability (from micrometer to millimeter level) under a low voltage (~1.0 V) was developed. And its actuation properties were enhanced effectively through a molecular-regulation strategy.
- Lu, Chao,Zhao, Lei,Hu, Yimin,Chen, Wei
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- Direct Partial Oxidation of Methane Catalyzed by an in Situ Generated Active Au(III) Complex at Low Temperature in Ionic Liquids
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An in situ generated AuIII catalyst is found to catalyze the direct oxidation of CH4 to C1 oxygenates in 1-ethylimidazolium bis-(trifluoromethylsulfonyl)amide ([Eim][NTf2]) at 90 °C. The formation of 13CH3OH and H13COOH from 13CH4 as a feed verifies the CH4 oxidation to CH3OH and HCOOH. Ionic liquids (ILs) with a wide range of structural types as potential reaction media and a number of solid, liquid, and gaseous oxidants are screened in a temperature range of 90-200 °C. Among the ILs and the oxidants, [Eim][NTf2] and hydrogen peroxide (H2O2) are identified to be compatible as the stable solvent and the most efficient oxidant, respectively, for the selective oxidation of CH4 to C1 oxygenates, with CH3OH as the primary product. An AuIII-CH4 H-bonding structure, produced in situ by adding two molar equivalent of silver trifluoromethanesulfonate (AgOTf) to the AuCl3(phen) (phen=phenanthroline) precursor under high CH4 pressure, forms a resting state of the AuIII catalyst, which produces CH3OH in the presence of H2O. After each catalytic turnover, AuI is oxidized by H2O2 to regenerate the active AuIII state. In the absence of CH4, unstable AuCl(OTf)2(phen) rapidly forms an orange-colored precipitate that shows no activity in CH4 activation. CH3OH overoxidation to HCOOH was dominantly catalyzed by potent Au0 species as a result of AuI disproportionation, which is the detrimental catalyst deactivation mechanism. Increasing CH4 pressure and H2O2 concentration successfully enhances the catalyst lifetime and significantly improves the CH4 oxidation efficiency with the improved CH3OH/HCOOH ratio. Density functional theory (DFT) calculations showed that (1) a C-H bond in CH4 was activated by forming AuIII-CH3 with a free energy barrier of 26.7 kcal/mol in a six-membered ring transition state and (2) AuIII-CH3 was functionalized to CH3OH by nucleophilic H2O with a free energy barrier of 29.1 kcal/mol or by MeOTf reductive elimination with a free energy barrier of 21.1 kcal/mol.
- Huang, Tingyu,Xu, Zhanwei,Yan, Peifang,Liu, Xiumei,Fan, Hongjun,Zhang, Z. Conrad
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- Revisiting the reactivity of tetrachloroauric acid with: N, N -bidentate ligands: Structural and spectroscopic insights
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The reactivity of tetrachloroauric acid (HAuCl4) with readily accessible bidentate N-donor ligands affords N,N-ligated Au(iii) center complexes. These compounds are useful precursors of stable catalysts, anticancer agents, and building blocks for materials. This report provides detailed insight into intermediates, equilibria, the counter anion effect, and structural variability, using spectroscopy, crystallography and computational tools. Novel mixed-valence Au(i) and Au(iii) complexes [Au(o-phen)Cl2]2[AuCl2][AuCl4] and [Au(o-phen)Cl2][AuCl2] having AuCl2- and AuCl4- anions linearly arranged in the axial sites of the square-planar Au(o-phen)Cl2 cation were discovered. Other competing side products of the reaction studied revealed protonated N,N-bidentate ligands with AuCl4- anions. Quantitative variable temperature NMR studies reveal that for a mixture of target Au(iii) salt and the protonated ligand, the reaction favors the irreversible formation of the side product. Using a rapid (30 min) temperature controlled protocol, the desired coordinated species is accessible in respectable yields while avoiding side products.
- Mertens, R. Tyler,Kim, Jong Hyun,Jennings, Will C.,Parkin, Sean,Awuah, Samuel G.
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- Spectroscopic and electrochemical properties of dichlorodiimine complexes of Au(III) and Pt(II) with 1,4-diazine derivatives of o-phenanthroline
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A series of dichlorodiimine complexes [M(N∧N)Cl2] z of Au(III) and Pt(II) with 1,4-derivatives of o-phenanthroline [(N∧N) = o-phenanthroline (phen), dipyrido[f,h]quinoxaline (dpq), dipyrido[a,c]phenazine (dppz), 6,7-dicyanodipyrido[f,h]quinoxaline (dicnq)] were prepared and characterized by 1H NMR, electronic absorption, and emission spectroscopy and by cyclic voltammetry. In all the complexes, the 3(π-π*)-type transition is the spin-forbidden transition of the lowest energy, responsible for the luminescence. The longest wave bands in the absorption spectra of the Au(III) and Pd(II) complexes were assigned in accordance with the results of the electrochemical studies to the 1(d*)-and 1(d*)-type transitions, respectively. Pleiades Publishing, Inc., 2006.
- Ivanov,Puzyk,Balashev
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- A novel high-stability Au(III)/Schiff-based catalyst for acetylene hydrochlorination reaction
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Herein, we reported on the application of an Au(III)/Schiff-based catalyst in acetylene hydrochlorination reaction. The [AuCl2(phen)]Cl catalyst exhibited excellent stability, and acetylene conversion was maintained at > 90% after 40 h of operation. The excellent stability of the [AuCl 2(phen)]Cl catalyst was attributed to the presence of the 1,10-phenanthroline ligand that partially inhibited the reduction of the Au 3 + active component.
- Huang, Chaofeng,Zhu, Mingyuan,Kang, Lihua,Dai, Bin
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- A novel high-stability Au(III)/Schiff-based catalyst for acetylene hydrochlorination reaction
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Herein, we reported on the application of an Au(III)/Schiff-based catalyst in acetylene hydrochlorination reaction. The [AuCl2(phen)]Cl catalyst exhibited excellent stability, and acetylene conversion was maintained at > 90% after 40 h of operation. The excellent stability of the [AuCl2(phen)]Cl catalyst was attributed to the presence of the 1,10-phenanthroline ligand that partially inhibited the reduction of the Au3 + active component.
- Huang, Chaofeng,Zhu, Mingyuan,Kang, Lihua,Dai, Bin
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