Gold Alkynyl Complexes Research Articles

Chemical speciation of methylmercury and mercury(II) cations in fish by new fluorogenic naphthalimide alkynyl gold complexes: The ultimate test for detecting fish contamination

The proof of concept of a new portable protocol for the detection and speciation of methylmercury and mercury(II) cations in fish samples is described. In this way, traces of methylmercury and/or mercury(II) cations in fish were quantitatively detected using an elaborated protocol and including a fluorescent sensor. In-the-field accurate results were obtained due to the selective behavior of the chemical sensor in the presence of both cations, working at very low concentrations of mercury species in fish under standard laboratory conditions, that are suitable for daily use in ordinary sampling by border companies importing fish or remote laboratories where large devices cannot be carried. The reported fish protocol is useful under real-life conditions for analyzing fish for the presence of methylmercury in contrast to total mercury analysis. The combination of the protocol and the fluorescent reporter constitutes the ultimate test for fish contamination by mercury(II) species in the workplace. The reported limits of detection of 0.72 nM for Hg2+ and 1.62 nM for CH3Hg+ and the closely related values of the two mercury(II) species in fish samples, obtained by ICP-MS analysis and fluorescent measurements, make the method suitable for daily control of methylmercury in fish under the EU legislation parameters and the WHO recommendations.

Publisher Correction: Probing the nature of gold-carbon bonding in gold-alkynyl complexes.

This corrects the article DOI: 10.1038/ncomms3223.

Alkynyl gold(I) phosphane complexes: Evaluation of structure–activity-relationships for the phosphane ligands, effects on key signaling proteins and preliminary in-vivo studies with a nanoformulated complex

Gold alkynyl complexes with phosphane ligands of the type (alkynyl)Au(I)(phosphane) represent a group of bioorganometallics, which has only recently been evaluated biologically in more detail. Structure–activity-relationship studies regarding the residues of the phosphane ligand (P(Ph)3, P(2-furyl)3, P(DAPTA)3, P(PTA)3, P(Et)3, P(Me)3) of complexes with an 4-ethynylanisole alkyne ligand revealed no strong differences concerning cytotoxicity. However, a relevant preference for the heteroatom free alkyl/aryl residues concerning inhibition of the target enzyme thioredoxin reductase was evident. Complex 1 with the triphenylphosphane ligand was selected for further studies, in which clear effects on cell morphology were monitored by time-lapse microscopy. Effects on cellular signaling were determined by ELISA microarrays and showed a significant induction of the phosphorylation of ERK1 (extracellular signal related kinase 1), ERK2 and HSP27 (heat shock protein 27) in HT-29 cells. Application of 1 in-vivo in a mouse xenograft model was found to be challenging due to the low solubility of the complex and required a formulation strategy based on a peanut oil nanoemulsion.

Synthesis, luminescence and electrochemical properties of luminescent dinuclear mixed-valence gold complexes with alkynyl bridges

A series of luminescent dinuclear mixed-valence gold alkynyl complexes was synthesized. Their photophysical properties can be tuned by varying the nature of the alkynyl bridges, as supported by computational studies.

Luminescent alkynyl-gold(i) coumarin derivatives and their biological activity

The synthesis and characterization of three propynyloxycoumarins are reported in this work together with the formation of three different series of gold(i) organometallic complexes. Neutral complexes are constituted by water soluble phosphines (PTA and DAPTA) which confer water solubility to them. The X-ray crystal structure of 7-(prop-2-in-1-yloxy)-1-benzopyran-2-one and its corresponding dialkynyl complex is also shown and the formation of rectangular dimers for the gold derivative in the solid state can be observed. A detailed analysis of the absorption and emission spectra of both ligands and complexes allows us to attribute the luminescent behaviour to the coumarin organic ligand. Moreover, the presence of the gold(i) metal atom seems to be responsible for an increase of coumarin phosphorescence emission. The biological activity of the complexes showed that the anionic complexes triggered strong cytotoxic effects in two different cell lines whereas the neutral gold alkynyl complexes led to lower effects against tumor cell growth. Thioredoxin reductase (TrxR) inhibition was very strong in the case of the neutral complexes (IC50 values below 0.1 μM) but moderate for the anionic complexes (IC50 values above 0.8 μM).

Probing the nature of gold–carbon bonding in gold–alkynyl complexes

Homogeneous catalysis by gold involves organogold complexes as precatalysts and reaction intermediates. Fundamental knowledge of the gold–carbon bonding is critical to understanding the catalytic mechanisms. However, limited spectroscopic information is available about organogolds that are relevant to gold catalysts. Here we report an investigation of the gold–carbon bonding in gold(I)–alkynyl complexes using photoelectron spectroscopy and theoretical calculations. We find that the gold–carbon bond in the ClAu–CCH− complex represents one of the strongest gold–ligand bonds—even stronger than the known gold–carbon multiple bonds, revealing an inverse correlation between bond strength and bond order. The gold–carbon bond in LAuCCH− is found to depend on the ancillary ligands and becomes stronger for more electronegative ligands. The strong gold–carbon bond underlies the catalytic aptness of gold complexes for the facile formation of terminal alkynyl–gold intermediates and activation of the carbon–carbon triple bond.

Organometallic Complexes for Non-Linear Optics. 51. Second- and Third-Order Non-Linear Optical Properties of Alkynylgold Complexes

The alkynes HC≡CC6H2-2,6-Et2-4-C≡CC6H4-4-NO2 (4) and HC≡CC6H4-4-C≡CC6H2-2,6-Et2-4-C≡CC6H4-4-NO2 (6) and gold alkynyl complexes Au{C≡CC6H2-2,5-(OEt)2-4-C≡CC6H4-4-NO2}(PPh3) (7), Au(C≡CC6H2-2,6-Et2-4-C≡CC6H4-4-NO2)(PPh3) (8), and Au(C≡CC6H4-4-C≡CC6H2-2,6-Et2-4-C≡CC6H4-4-NO2)(PPh3) (9) have been synthesized. The linear optical properties and quadratic optical non-linearities of 7–9 have been measured, the latter by hyper-Rayleigh scattering at 1064 nm, and compared with data for the previously reported complexes Au(C≡CC6H4-4-NO2)(PPh3) (10) and Au(C≡CC6H4-4-C≡CC6H4-4-NO2)(PPh3) (11). The optical absorption maximum red-shifts and the first hyperpolarizabilities increase on π-system lengthening and on introduction of electron-releasing substituents on the π-bridge ring adjacent to the metal centre. The cubic non-linear optical properties of 1,4-{(PCy3)Au(C≡C)}2C6H4 (12) and {(PCy3)Au(C≡C-4-C6H4C≡C)}6C6 (13) have been assessed by wide spectroscopic range femtosecond Z-scan studies; the maximal values of the imaginary component and the effective two-photon absorption cross-section increase markedly on proceeding from linear complex 12 to 6-fold-symmetric complex 13, an increase that is maintained when data are scaled by relative molecular weight.

P–H activation using alkynylgold substrates: steric and electronic effects

The susceptibility of a prototypical hydrogen phosphonate to undergo P-H activation upon treatment with alkynylgold complexes has been studied. Dynamic solution behavior was observed during reactions involving triphenylphosphine ligated substrates and was attributed to rapid phosphine exchange between the alkynylgold starting material and the gold phosphonate product. The use of bulky biaryldialkylphosphine ligands eliminated the fluxional behavior, but did not significantly slow the rate of P-H activation. Similarly, changing the supporting ligand to an N-heterocyclic carbene did not significantly slow the rate of the reaction. Despite a number of reports outlining the functionalization of propargyl alcohols using gold catalysts, incorporating these groups into the architecture of the alkynylgold substrates did not alter the product distributions. Although the chemistry tolerated a range of supporting ligands, incorporating electron donating groups into the alkyne increased the rate of the reaction while electron-withdrawing groups slowed the reaction. A possible mechanism for the process includes a transition state containing significant pi-contribution from the alkyne. Due to the high yields of gold phosphonates obtained in this chemistry as well as the mild conditions of the reactions, the interception of intermediates/catalysts by substrates or ligands containing labile P-H donors is an issue that must be circumvented when designing or developing a gold catalyzed reaction that proceeds through alkynylgold intermediates.

Synthesis, Characterization, and Properties of Binuclear Gold(I) Phosphine Alkynyl Complexes

Reactions of gold salts with various π-conjugated dialkynes have led to two homologous series of binuclear alkynylgold(I) complexes, linear rigid-rod Cy3PAu−C≡C−(CH═CH)n−C≡C−AuPCy3 (n = 1−3, all-trans) (2a−c) and photochromic LAu−C≡C−DTE−C≡C−AuL (DTE = 1,2-di(2-methylthien-3-yl)cyclopentene or 1,2-di(2-methylthien-3-yl)-3,3,4,4,5,5-hexafluorocyclopentene) (L = PCy3, tricyclohexylphosphine or PPh3, triphenylphosphine) (4a−d). The photophysical properties of these complexes have been investigated. The emission spectra exhibited a progressive red-shift with increasing length of the bridge between the two Au(I) in the linear metal complexes 2. Photochromic alkynylgold(I) complexes 4 also exhibited fluorescence properties, and the emission wavelength was found to change upon variation of the dithienylethene (DTE) linkers as well as of the auxiliary phosphine ligands. It is revealed that the binuclear alkynylgold complexes with DTE units show photochromic behavior and that the efficiencies of the photochromic p...

New rhodium(I) supramolecular structures containing pyridyl and bipyridyl ligands

The use of dimeric [RhCl(CO) 2] 2 as acceptor unit in the construction of mono-, bi- and three-dimensional metallosupramolecular structures is reported. The reaction of the dimer with the alkynylgold complex [Au(C CC 5H 4N)(CNC 6H 4O(O)CC 6H 4OC 10H 21)] resulted in the mononuclear rhodium complex 1, through an unexpected transfer of the isonitrile ligand from the gold to the rhodium centres. The reaction of the linear unit [RhCl(CO) 2] 2(μ-4,4′-bipy) ( 3) with the diphosphine 1,4-bis(diphenylphosphino)butane (dppb) yielded the simultaneous formation of both metallomacrocycles [RhCl(CO)(dppb)] 2 ( 4) and {[RhCl(CO)] 2(μ-4,4′-bipy)} 2(μ-dppb) 2 ( 5). The use of a diphosphine with smaller bite angle, 1,1′-bis-(diphenylphosphino)methane, (dppm) formed the three-dimensional {[RhCl(CO)] 2(μ-4,4′-bipy)} 2(μ-dppm) 4 complex ( 6) that incorporates four diphosphine units connecting two [RhCl(CO) 2] 2(μ-bipy) linear edges. PM3 semi-empirical method has been used to calculate the optimised geometry of compound 6.

Intensely Luminescent Alkynyl−Phosphine Gold(I)−Copper(I) Complexes: Synthesis, Characterization, Photophysical, and Computational Studies

The reactions between the diphosphino-alkynyl gold complexes (XC6H4C2Au)PR2-C6H4-PR2(AuC2C6H4X) with Cu+ lead to the formation of a family of heterometallic clusters of the general formula [{Au3Cu2(C2C6H4X)6}Au3(PR2C6H4PR2)3][PF6]2 (X = NO2, H, OMe, NMe2; R = C6H5, NC4H4). These complexes adopt the same structural pattern and consist of a heterometallic alkynyl cluster [Au3Cu2(C2C6H4X)6]- "wrapped" by the cationic [Au3(PR2C6H4PR2)3]3+ "belt". The novel compounds were characterized by NMR spectroscopy and ESI-MS measurements. A systematic study of their luminescence properties revealed efficient room-temperature phosphorescence in solution with remarkably weak quenching by molecular oxygen. The photophysical experiments demonstrate that the increase in the electron donor ability of the alkynyl ligands and the electron-withdrawing character of the diphosphines results in the bathochromic shift of emission maxima (in the 576-686 nm range) and a decrease in the luminescence quantum yield. The electronic structure calculations showed that variations of X or R substituents have very little effect on the structural parameters but display a significant influence on the electronic properties of the clusters and characteristics of luminescence. The metal-centered triplet emission within the heterometallic alkynyl cluster is suggested to play a key role in the observed phosphorescence.

Preparation and Structures of Several Complexes Containing Carbon-Rich Ligands Attached to Polynuclear Metal Carbonyls

Several new gold-containing cluster complexes have been prepared from the reactions of gold alkynyl complexes, LnM-Cx-Au(PPh3), (x = 3, 4, 6) with Ru3(CO)10(NCMe)2. The bis-cluster complex 1,4-{AuRu3(CO)9(PPh3)(μ3-C2)}2C6H4 was obtained from Ru3(CO)10(NCMe)2 and 1,4-{(Ph3P)Au(C≡C)}2C6H4. The complexes Ru3(μ-H){μ3-C2C≡C[Ru(PP)Cp′]}(CO)9 [PP = (PPh3)2, Cp′ = Cp; PP = dppe, Cp′ = Cp*] were also obtained as minor by-products and synthesised independently from Ru(C≡CC≡CH)(PP)Cp′. A reaction between Co3{μ3-CC≡CC≡CAu(PPh3)}(μ-dppm)(CO)7 and Ru3(CO)12 afforded {(Ph3P)(OC)9AuRu3}C≡CC≡CC{Co3(μ-dppm)(CO)7} 7. Related complexes AuRu3{μ3-C2C≡[M(CO)2Tp]}(CO)9(PPh3) (M = Mo 8, W 9) were obtained from {Tp(OC)2M}≡CC≡C{Au(PPh3)}, while the mixed metal cluster complexes MoM2(C2Me)(CO)8Tp (M = Ru 13, Fe 14) were obtained from M(≡CC≡CSiMe3)(CO)2Tp (M = Mo, W) with Fe2(CO)9 and Ru3(CO)12, respectively. Reactions of the Mo carbyne complex with Co2(LL)(CO)6 [LL = (CO)2, μ-dppm] or nickelocene afforded complexes 15–17 in which Co2 and Ni2 fragments, respectively, had coordinated to the C≡C triple bond. XRD structural determinations of 7, 8, 14, 16 and {Tp(OC)2W}≡CC≡CC≡{Co3(μ-dppm)(CO)7} (18-W) are reported.