Triphenylphosphine Gold Research Articles

Intramolecular gold–oxygen and gold–sulfur contacts and intermolecular gold–sulfur and aurophilic interactions in X-ray crystal structures of triphenylphosphine gold(I) thiolate, dithiocarbonate and dithiocarbamate complexes

Intramolecular gold–oxygen and gold–sulfur contacts and intermolecular gold–sulfur and aurophilic interactions in X-ray crystal structures of triphenylphosphine gold(I) thiolate, dithiocarbonate and dithiocarbamate complexes

Synthesis and Characterization of Magnetoplasmonic Air-Stable Au@FeCo

The synthesis of FeCo alloys as highly magnetic nanoparticles has been valuable, as far as applications for magnetic nanoparticles are concerned. However, recently, a field of magnetoplasmonics in which magnetic nanoparticles such as the FeCo alloys doped with plasmonic materials such as Au and Ag to create a hybrid nanostructure with both properties has emerged. These magnetoplasmonic metamaterials have greatly enhanced the limit of detection of analytes in spectroscopic methods, as well as providing a more widely applicable nanoparticle to broaden the use of FeCo alloys even further. Herein, we discuss the synthesis of high-yield and fairly monodisperse spherical FeCo and Au-doped FeCo (Au@FeCo) with varying compositions of Au synthesized via the thermal decomposition of iron pentacarbonyl (Fe(CO)5) and dicobalt octacarbonyl (Co2(CO)8), followed by the addition of Au atoms using triphenylphosphine gold(I) chloride ((Ph3P)AuCl) via both coprecipitation and by delayed addition methods. The products were separated using a hand-held magnet, and then characterized via ultraviolet-visible light (UV-vis), scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), flame atomic absorption spectrometry (F-AAS), and magnetization measurements. Optical studies revealed a plasmonic peak at 550 nm in the Au@FeCo nanoparticles that had a gold content (%Au) of >2% (by weight), determined using F-AAS. Colocation of the Fe, Co, and Au were demonstrated through EDX analysis. Location of the Au atoms in the core were seen through high-resolution bright-field imaging. To understand the use of these nanoparticles for potential application in therapeutics and/or electronics, resistance measurements were performed to assess power loss as a function of frequency. We also achieved magnetization values as high as 150 emu/g and as low as 50 emu/g for gold-loaded samples based on %Au by weight. This paves the way to continue to develop magneto-plasmonic structures chemically using these synthesis strategies.

Photosensitizer-free, visible light-mediated recyclable gold-catalyzed cross-coupling of aryldiazonium salts and alkynyltrimethylsilanes

Photosensitizer-free visible light-mediated cross-coupling of aryldiazonium tetrafluoroborates and alkynyltrimethylsilanes has been achieved using a recyclable SBA-15-anchored triphenylphosphine–gold(i) complex as a catalyst.

Triphenylphosphine gold(I) derivatives promote antiviral effects against the Chikungunya virus.

Herein a systematic series of four [AuLL']n+ n=0, +1 complexes, where L=1,3-bis(mesityl)imidazole-2-ylidene (IMes), or triphenylphosphine (PPh3), and L' = chloride, or 4-dimethylaminopyridine (DMAP), had their in vitro antiviral activity assessed against Chikungunya virus (CHIKV). The PPh3 derivatives inhibited viral replication by 99%, whereas the IMes derivatives about 50%. The lipophilicity of the PPh3 derivatives is higher than the IMes-bearing compounds, which can be related to their more prominent antiviral activities. The dissociation of DMAP is faster than chloride in solution for both IMes and PPh3 derivatives; however, it does not significantly affect their in vitro activities, showing a higher dependence on the nature of L rather than L' towards their antiviral effects. All complexes bind to N-acetyl-L-cysteine, with the Ph3P-bearing complexes coordinating at a faster rate to this amino acid. The binding constants to bovine serum albumin are in the order of 104, slightly higher for the DMAP complexes in both PPh3 and IMes derivatives. Mechanistic investigations of the PPh3 complexes showed a ubiquitous protective effect of the compounds in the pretreatment, early stages, and post-entry assays. The most significant inhibition was observed in post-entry activity, in which the complexes blocked viral replication in 99%, followed by up to 95% inhibition of the early stages of infection. Pretreatment assays showed a 92% and 80% replication decrease for the chloride and DMAP derivatives, respectively. dsRNA binding assays showed a significant interaction of the compounds with dsRNA, an essential biomolecule to viral replication.

Directing the Crystal Packing in Triphenylphosphine Gold(I) Thiolates by Ligand Fluorination.

We explore herein the supramolecular interactions that control the crystalline packing in a series of fluorothiolate triphenylphosphine gold(I) compounds with the general formula [Au(SRF)(Ph3P)] in which Ph3P = triphenylphosphine and SRF = SC6F5, SC6HF4-4, SC6F4(CF3)-4, SC6H3F2-2,4, SC6H3F2-3,4, SC6H3F2-3,5, SC6H4(CF3)-2, SC6H4F-2, SC6H4F-3, SC6H4F-4, SCF3, and SCH2CF3. We use for this purpose (i) DFT electronic structure calculations and (ii) the quantum theory of atoms in molecules and the non-covalent interactions index methods of wave function analyses. Our combined experimental and computational approach yields a general understanding of the effects of ligand fluorination in the crystalline self-assembly of the examined systems, in particular, about the relative force of aurophilic contacts compared with other supramolecular interactions. We expect this information to be useful in the design of materials based on gold coordination compounds.

In situ derivatization of Au nanoclusters via aurophilic interactions of a triphenylphosphine gold(i) salt with neurotransmitters and their rapid MALDI-TOF-MS detection in mice brain tissue extracts.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) has attracted much attention for the detection of small molecules such as neurotransmitters due to its softness, high sensitivity, extensive compatibility and diverse mass analyzers. However, it has been really a difficult challenge to develop a highly specific organic compound as a matrix for the rapid, sensitive and selective detection of neurotransmitters. Herein, we report tris(triphenylphosphine)gold oxonium tetrafluoroborate ([Ph3PAu]3O+BF4-) for the first time as an efficient matrix for the rapid and simultaneous MALDI-MS detection of neurotransmitters. [Ph3PAu]3O+BF4- facilitates the in situ derivatization of gold nanoclusters (Au NCLs) during the interaction with neurotransmitters, which increases their ionization energy by absorbing more ultra-violet (UV) radiation during MALDI-TOF-MS detection. The results show that this [Ph3PAu]3O+BF4- matrix can exhibit a 10-fold faster response time compared to previously reported pyrylium matrices. In addition, [Ph3PAu]3O+BF4- can also provide the simultaneous derivatization of various neurotransmitters, including dopamine (DA), noradrenaline (NAd), serotonin (5-HT), γ-aminobutyric acid (GABA), histamine (H) and tyramine (TY), in mice brain tissue extracts, which can be detected in the MALDI-TOF-MS spectra.

A Polystyrene‐Bound Triphenylphosphine Gold(I) Catalyst for the Glycosylation of Glycosyl ortho‐Hexynylbenzoates

AbstractThe efficacy of the heterogeneous polystyrene‐bound triphenylphosphine gold(I) catalyst 3 (PS‐[Ph3PAuINTf2]; PS=polystyrene; Tf=trifluoromethanesulfonyl) in the activation of glycosyl ortho‐hexynylbenzoates for glycosylation is demonstrated. The shelf‐stable catalyst 3 (and its precursor 2, PS‐[Ph3PAuICl]) were fully characterized by elemental analysis, X‐ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM), and showed remarkable catalytic activities and recyclability in glycosylation reactions as well as in the skeletal rearrangement of the 1,6‐enyne 4. EDS analysis demonstrated that the phosphine ligand binds the gold strongly and prevents the leaching of the metal.

Structural Conversion of a Triphenylphosphine Gold Cluster by Octahedral Metal Complexes with 2-Aminoethanethiolate

Abstract The reaction of [Au9(PPh3)8]3+ with fac-[Ir(aet)3] (aet: 2-aminoethanethiolate) led to the structural conversion to [Au8(PPh3)8]2+ with the concomitant formation of [Au3{Ir(aet)3}2]3+. A similar structural conversion was also observed when [Au9(PPh3)8]3+ was reacted with fac-[Rh(aet)3] or fac-[Co(aet)3]. This result demonstrates for the first time that thiolato metal complexes possess an ability to abstract gold atoms, rather than to replace phosphine ligands in a gold cluster.

Hydrophobic gold catalysts: From synthesis on passivated silica to synthesis on few-layer graphene

Hydrophobic gold catalysts have recently proven useful in increasing the efficiency of the aerobic oxidation of hydrocarbons in apolar liquid media. Catalytically active 3nm gold nanoparticles can be dispersed on the surface of commercially available methyl-terminated silica by performing chemical reduction of triphenylphosphine gold(I) chloride in the presence of the support in an ethanol/dichloromethane mixture. This method is here applied to a home-made few-layer graphene which displays a pristine graphitic surface, as shown by thermogravimetric analysis. Since direct application of the protocol leads to much larger gold particles, the protocol of synthesis is subsequently adapted to the specific nature of the graphene support, in particular by performing the reaction under sonication. Further studies of the effect of several reaction parameters on both the average gold crystallite size determined by XRD and the deposition yields determined by elemental analysis reveal (1) the superiority of DMF in minimizing the gold particle size and (2) the impact of short reduction times on maximizing the deposition yields. Repeatability of the experiment is ensured by the development of an optimized protocol of synthesis, and in particular the identification of the most effective positions in the sonication bath.

Isomorphism in the structural chemistry of two-coordinate adducts of diphenyl(2-formylphenyl)phosphine and triphenylphosphine with gold(I) halides

Single crystal X-ray structure determinations are recorded for diphenyl(2-formylphenyl)phosphine gold(I) halides [Ph2(Ph-CHO)PAuX], X=Cl, Br and I, and for redeterminations of enhanced precision for triphenylphosphine gold(I) halides [Ph3PAuX], X=Cl, Br, I, and SCN0.91Br0.09. These complexes, other than [Ph2(Ph-CHO)PAuCl], together with a diverse array of other structures, crystallize as an isomorphous series in the orthorhombic space group P212121a=9.804(1)–11.906(3), b=11.771(2)–12.996(3) and c=12.871(1)–14.169(3)Å. In these complexes, introduction of the formyl group results in only minor differences between the conformations of the two phosphine ligands and the corresponding Au–P, Au–X, and Au–P–X bond lengths and angles. The crystal packings of [Ph3PAuX] for X=Cl, Br, I and of [Ph2(Ph-CHO)PAuX] for X=Br and I show that, while these structures are isomorphous, different supramolecular synthons may be present, suggesting global packing considerations are all-important rather than specific supramolecular interactions. This is borne out by the different packing found for the centrosymmetric [Ph2(Ph-CHO)PAuCl] structure. Crystallization of the mixed anion structure [Ph3PAuSCN0.91Br0.09] in the above P212121 lattice rather than the P21/c lattice reported for pure [Ph3PAuSCN] suggests that co-crystallization with bromide may impose constraints on packing considerations which favor crystallization in the P212121 lattice.

Absence of exchange interaction between localized magnetic moments and conduction-electrons in diluted Er3+ gold-nanoparticles

The Electron Spin Resonance (ESR) of diluted Er3+ magnetic ions in Au nanoparticles (NPs) is reported. The NPs were synthesized by reducing chloro triphenyl-phosphine gold(I) and erbium(III) trifluoroacetate. The Er3+ g-value along with the observed hyperfine splitting indicate that the Er3+ impurities are in a local cubic symmetry. Furthermore, the Er3+ ESR spectra show that the exchange interaction between the 4f and the conduction electrons (ce) is absent or negligible in Au1–xErx NPs, in contrast to the ESR results in bulk Au1–xErx. Therefore, the nature of this interaction needs to be reexamined at the nano scale range.

Bis(triphenylphosphine)gold(I) Perrhenate

Bis(triphenylphosphine)gold(I) perrhenate [Ph3PAuPPh3]+ReO4 - has been prepared in high yield from Ph3PAuCl, Ph3P and AgReO4 in a mixed solvent. The compound is stable in air and decomposes at 235 °C. In the crystal structure, the two independent perrhenate anions are not approaching the gold centers of the two independent cations, but weak interionic interactions are entertained via π-π stacking of phenyl groups and C-H···O contacts. As three-blade chiral rotors, the Ph3P ligands of the cations are in a staggered conformation at the gold atoms with only slightly bent P-Au-P axes. IR and NMR data show no anomalies and are close to those of alkali or onium perrhenates.

Gold(I)-Phosphine-N-Heterocycles: Biological Activity and Specific (Ligand) Interactions on the C-Terminal HIVNCp7 Zinc Finger

The syntheses and the characterization by chemical analysis, (1)H and (31)P NMR spectroscopy, and mass spectrometry of a series of linear triphenylphosphine gold(I) complexes with substituted N-heterocycle ligands (L), [(PPh3)Au(I)(L)](+), is reported. The reaction of [(PPh3)Au(L)](+) (L = Cl(-) or substituted N- heterocyclic pyridine) with the C-terminal (Cys3His) finger of HIVNCp7 shows evidence by mass spectrometry (ESI-MS) and (31)P NMR spectroscopy of a long-lived {(PPh3)Au}-S-peptide species resulting from displacement of the chloride or pyridine ligand by zinc-bound cysteine with concomitant displacement of Zn(2+). In contrast, reactions with the Cys2His2 finger-3 of the Sp1 transcription factor shows significantly reduced intensities of {(PPh3)Au} adducts. The results suggest the possibility of systematic (electronic, steric) variations of "carrier" group PR3 and "leaving" group L as well as the nature of the zinc finger in modulation of biological activity. The cytotoxicity, cell cycle signaling effects, and cellular accumulation of the series are also reported. All compounds display cytotoxicity in the micromolar range upon 96 h continuous exposure to human tumor cells. The results may have relevance for the reported inhibition of viral load in simian virus by the gold(I) drug auranofin.

Gold nanoparticles on wool in a comparative study with molecular gold catalysts

The catalytic activity of gold chloride nanoparticles is compared to the activity of two molecular gold(I) chloride phosphine complexes for the addition of methanol to 3-hexyne. The phosphines are triphenylphosphine and the bispidinone related bulky 6,8-bis-(4-dimethylamino-phenyl)-3-methyl-9-oxo-7-phenyl-3-aza-7-phospha-bicyclo[3.3.1]nonan-1,5-dicarboxylic acid dimethyl ester. Use of the bulky ligand made the addition reaction selective towards the enol product, meaning that no addition of methanol or water to alkenes, which were produced during the reaction, occurred. In contrast, use of triphenylphosphine gold(I) chloride resulted in the synthesis of a variety of products. The phosphines decomposed during reaction leading to the formation of gold nanoparticles, which were found to be catalytically inactive. Artificially produced gold nanoparticles also proved to be inactive. In contrast, gold chloride nanoparticles deposited on wool were active comparable to the gold phosphine-containing catalysts tested previously. Overall activities observed were low compared to results from the literature suggesting that the operating conditions chosen could be optimised.

Electrochemical monitoring of the oxidative coupling of alkynes catalyzed by triphenylphosphine gold complexes

Electrochemical monitoring of the oxidative coupling of alkynes in the homogeneous phase through catalytic cycles involving triphenylphosphine gold complexes and selectfluor as oxidant reveals that at least two gold species in +3 and +1 oxidation states are implicated. Electrochemically driven homocoupling of terminal alkynes using molecular oxygen as the oxidant can be performed using such catalysts.

Gold-catalyzed aerobic epoxidation of trans-stilbene in methylcyclohexane. Part I: Design of a reference catalyst

The kinetics of the heterogeneous gold-catalyzed aerobic epoxidation of stilbene in the liquid phase has been shown to be hindered by diffusion limitations, due to the use of supports which are unsuitable to apolar reaction media. The choice of these supports is generally dictated by the ability of standard methods of preparation to stabilize highly dispersed gold nanoparticles on them. Hence, new methods need to be designed in order to produce catalytically active gold nanoparticles on hydrophobic supports in general and on passivated silicas in particular. By investigating Tsukuda's method to produce colloidal solutions of gold nanoparticles upon reduction of the triphenylphosphine gold chloride complex in solution, we found that direct reduction of AuPPh 3Cl in the presence of a commercially available silica support functionalized with dimethylsiloxane, Aerosil R972, leads, in a highly reproducible and potentially scalable way, to the best catalyst ever reported for this reaction.

Cycloisomerization of (arene)chromium complexes with enyne by gold(I) catalyst for axially chiral biaryls

Planar chiral arene chromium complexes with enyne bond gave stereoselectively axial biaryl chromium complexes by gold(I) catalyzed cycloisomerization in good yields. Arene chromium complexes with enyne bonds were treated with triphenylphosphine gold bis(trifluoromethanesulfonyl)imidate in methylene chloride to give anti-biaryl monochromium complexes without formation of stereoisomers.

Chromium, iron, ruthenium and gold complexes of 3,3-(biphenyl-2,2′-diyl)-1-diphenylphosphino-1-phenylallene: A versatile ligand

Successive treatment of 9-(phenylethynyl)fluoren-9-ol ( 1a), with HBr, butyllithium and chlorodiphenylphosphine furnishes 3,3-(biphenyl-2,2′-diyl)-1-diphenylphosphino-1-phenylallene ( 5). Moreover, reaction of 1a directly with chlorodiphenylphosphine yields the corresponding allenylphosphine oxide ( 6). The allenylphosphine ( 5), and Fe 2(CO) 9 initially form the phosphine–Fe(CO) 4 complex, 11, which is very thermally sensitive and readily loses a carbonyl ligand. In the resulting phosphine–Fe(CO) 3 system, 12, the additional site at iron is coordinated by the allene double bond adjacent to phosphorus; the Fe(CO) 3 tripod in 12 exhibits restricted rotation on the NMR time-scale even at room temperature. The corresponding chromium complex, ( 5)-Cr(CO) 5 ( 9), has also been prepared. The gold complexes ( 5)-AuCl ( 13), and [( 5)-Au(THT)] + X −, where (THT) is tetrahydrothiophene, and X = PF 6 ( 14a), or ClO 4 ( 14b), are analogous to the known triphenylphosphine–gold complexes. In contrast, in the (arene)(allenylphosphine)RuCl 2 system the allene double bond adjacent to phosphorus displaces a chloride, and the resulting cationic species undergoes nucleophilic attack by water yielding ultimately a five-membered Ru–P–C C–O ruthenacycle ( 17). Thus, the allenylphosphine ( 5), reacts initially as a conventional mono-phosphine but, when the metal centre has a readily displaceable ligand such as a carbonyl or halide, the allene double bond adjacent to the phosphorus can also function as a donor. X-ray crystal structures are reported for 5, 6, 11, 12, 13, 14a, 14b and 17.

Photophysics and photochemistry of biphenylyl triphenylphosphine gold(I) complexes

Biphenylyl triphenylphosphine gold(I) complexes (4-biphenylyl, 4B; 2-biphenylyl, 2B) having the Au–C bond are synthesized. The 4B complex is found to exhibit intense blue phosphorescence ( Φ p = 0.24 and τ T = 117 μs) at room temperature originated from the locally excited triplet of the biphenyl moiety ( 3LE) in both solid states and a degassed 2-methyltetrahydrofuran solution. 2B, however, is nonluminescent. The homolytic cleavage of the Au–C bond in dichloromethane solution of 4B upon UV irradiation is also reported.

Sublethal concentrations of diverse gold compounds inhibit mammalian cytosolic thioredoxin reductase (TrxR1)

Thioredoxin reductase (TrxR) reduces thioredoxin (Trx), thereby contributing to cellular redox balance, facilitating the synthesis of deoxy-ribose sugars for DNA synthesis, and regulating redox-sensitive gene expression. Auranofin is a gold compound that potently inhibits TrxR. This inhibition is one suspected mechanism of auranofin’s therapeutic benefit in the treatment of rheumatoid arthritis. The use of other gold compounds to treat cancer or inflammatory disease may rely on their ability to inhibit TrxR. In the current study, we tested the hypothesis that a variety of gold compounds may inhibit TrxR. Methods: We exposed rat-TrxR1 to auranofin, gold sodium thiomalate, sodium aurothiosulfate, triphenyl phosphine gold chloride, or gold acetate, and measured TrxR activity ex vivo. We then compared TrxR1 inhibitory levels of gold compounds to those that inhibited mitochondrial activity of THP1 monocytes and OSC2 epithelial cells, estimated by succinate dehydrogenase activity. Results: All gold compounds inhibited TrxR1 at concentrations ranging from 5 to 4000 nM (50% inhibitory concentration). The oxidation state of gold did not correlate with inhibitory potency, but ligand configuration was important. Au(I)-phosphine compounds (triphenyl phosphine gold chloride and auranofin) were the most potent inhibitors of TrxR. All TrxR1 inhibitory concentrations were sublethal to mitochondrial activity in both THP1 and OSC2 cells. Conclusions: Diverse types of gold compounds may be effective inhibitors of TrxR1 at concentrations that do not suppress cellular mitochondrial function. Inhibition may be optimized to some degree by altering the ligand configuration of the compounds. These results support future study of a variety of Au compounds for therapeutic development as inhibitors of TrxR1.