Au Compounds Research Articles

Study of optoelectronic and thermoelectric properties of K2XSbCl6 (X= In, Au) double perovskites for energy conversion devices: A DFT insight

Density functional theory (DFT) method based on first principles calculations are performed to explore the novel halide perovskites K2InSbCl6 and K2AuSbCl6. This study explores them for the first time to investigate their structural, electronic, optical, and thermoelectric properties. After relax the structure, we computed some parameters such as lattice constant (21.2195, 20.256) bohr, ground states energy (−32681.329187 eV, −59010.453287 eV), and formation energy (−2.06 eV, −1.433 eV) observed for K2XSbCl6 (X = In, Au) compounds respectively. The K2InSbCl6 reveals a direct band gap (1.03 eV), while K2AuSbCl6 shows an indirect band gap (1.01 eV). Hence, both materials express semiconducting behavior. Furthermore, the calculated optical characteristic is favorable for optoelectronics devices. The real dielectric function ε1(ω) for K2XSbCl6 (X = In, Au) 4.0 and 4.25 and the absorption coefficient shows maximum absorption in the visible region. The thermometric response of both compounds is calculated with Boltzmann's theory. To check the material efficiency, considered the thermal parameters, electrical conductivity, thermal conductivity, Seebeck coefficient, and power factor. The zT values of K2InSbCl6 is 0.74 and 0.77 for K2AuSbCl6. The present study of these novel compounds provides an overview of the physical properties of optoelectronics and thermoelectric applications.

The Synthesis and Crystallographic Characterization of Emissive Pt(II) and Au(I) Compounds Exploiting the 2-Ethynylpyrimidine Ligand

The luminescent properties of Au(I) and Pt(II) compounds are commonly tuned by exploiting the alkynyl ligand with varying electron density. Herein, we describe the synthesis of three new emissive transition metal compounds, tbpyPt(C2pym)2, Ph3PAuC2pym, and Cy3PAuC2pym (where HC2pym = 2-ethynylpyrimidine), verified by 1H-NMR, EA, and a single-crystal X-ray diffraction analysis. The tbpyPt(C2pym)2 complex crystallized as an Et2O solvate in the orthorhombic space group Pbca with Z = 24 with three unique Pt(II) species within the unit cell. The Cy3PAuC2pym species crystallizes in a monoclinic space group with one unique complex in the asymmetric unit. Changing the identity of the phosphine from Cy3P to Ph3P influences interactions within the unit cell. Ph3PAuC2pym, which also crystalizes in a monoclinic space group, has an aurophilic bonding interaction Au–Au distance of 3.0722(2) Å, which is not present in crystalline Cy3PAuC2pym. Regarding optical properties, the use of an electron-deficient heterocycle provides an alternate approach to blue-shifting the emission of Pt(II) transition metals’ compounds, where the aryl moiety is made more electron-deficient by exploiting nitrogen within this moiety instead of the typical strategy of decorating the aryl ring with electron withdrawing substituents (e.g., fluorines). This is indicated by the blue-shift in emission that occurs in tbpyPt(C2pym)2 (λmax, emission = 512 nm) compared to the previously reported tbpyPt(C22-py)2 (where HC22-py = 2-ethynylpyridine) complex (λmax, emission = 520 nm).

Consolidation of the Oxidant-Free Au(I)/Au(III) Catalysis Enabled by the Hemilabile Ligand Strategy.

In this minireview we survey the challenges and strategies in gold redox catalysis. Gold's reluctance to oxidative addition reactions due to its high redox potential limits its applicability. Initial attempts to overcome this problem focused on the use of sacrificial external oxidants in stoichiometric amounts to bring Au(I) compounds to Au(III) reactive species. Recently, innovative approaches focused on employing hemilabile ligands, which are capable of coordinating to Au(I) and stabilizing square-planar Au(III) intermediates, thus facilitating oxidative addition steps and enabling oxidant-free catalysis. Notable examples include the use of the (P^N) bidendate MeDalphos ligand to achieve various cross-coupling reactions via oxidative addition Au(I)/Au(III). Importantly, hemilabile ligand-enabled catalysis allows merging oxidative addition with π-activation, such as oxy- and aminoarylation of alkenols and alkenamines using organohalides, expanding gold's versatility in C-C and C-heteroatom bond formations and unprecedented cyclizations. Moreover, recent advancements in enantioselective catalysis using chiral hemilabile (P^N) ligands are also surveyed. Strikingly, versatile bidentate (C^N) hemilabile ligands as competitors of MeDalphos have appeared recently, by designing scaffolds where phosphine groups are substituted by N-heterocyclic or mesoionic carbenes. Overall, these approaches highlight the evolving landscape of gold redox catalysis and its tremendous potential in a broad scope of transformations.

Consolidation of the Oxidant‐Free Au(I)/Au(III) Catalysis Enabled by the Hemilabile Ligand Strategy

AbstractIn this minireview we survey the challenges and strategies in gold redox catalysis. Gold's reluctance to oxidative addition reactions due to its high redox potential limits its applicability. Initial attempts to overcome this problem focused on the use of sacrificial external oxidants in stoichiometric amounts to bring Au(I) compounds to Au(III) reactive species. Recently, innovative approaches focused on employing hemilabile ligands, which are capable of coordinating to Au(I) and stabilizing square‐planar Au(III) intermediates, thus facilitating oxidative addition steps and enabling oxidant‐free catalysis. Notable examples include the use of the (P^N) bidendate MeDalphos ligand to achieve various cross‐coupling reactions via oxidative addition Au(I)/Au(III). Importantly, hemilabile ligand‐enabled catalysis allows merging oxidative addition with π‐activation, such as oxy‐ and aminoarylation of alkenols and alkenamines using organohalides, expanding gold‘s versatility in C−C and C‐heteroatom bond formations and unprecedented cyclizations. Moreover, recent advancements in enantioselective catalysis using chiral hemilabile (P^N) ligands are also surveyed. Strikingly, versatile bidentate (C^N) hemilabile ligands as competitors of MeDalphos have appeared recently, by designing scaffolds where phosphine groups are substituted by N‐heterocyclic or mesoionic carbenes. Overall, these approaches highlight the evolving landscape of gold redox catalysis and its tremendous potential in a broad scope of transformations.

A gold-based inhibitor of oxidative phosphorylation is effective against triple negative breast cancer

Triple-negative breast cancer (TNBC) is associated with metabolic heterogeneity and poor prognosis with limited treatment options. New treatment paradigms for TNBC remains an unmet need. Thus, therapeutics that target metabolism are particularly attractive approaches. We previously designed organometallic Au(III) compounds capable of modulating mitochondrial respiration by ligand tuning with high anticancer potency in vitro and in vivo. Here, we show that an efficacious Au(III) dithiocarbamate (AuDTC) compound induce mitochondrial dysfunction and oxidative damage in cancer cells. Efficacy of AuDTC in TNBC mouse models harboring mitochondrial oxidative phosphorylation (OXPHOS) dependence and metabolic heterogeneity establishes its therapeutic potential following systemic delivery. This provides evidence that AuDTC is an effective modulator of mitochondrial respiration worthy of clinical development in the context of TNBC. One sentence summaryMetabolic-targeting of triple-negative breast cancer by gold anticancer agent may provide efficacious therapy.

First-principles calculations to investigate structural, elastic, electronic, optical and thermal properties of La-based ternary intermetallic superconductors LaM2Si2 (M=Co, Cu, Rh, Pd, Ag, Ir, Pt, Au)

Different physical properties of ternary intermetallic La-based superconducting materials LaM2Si2 (M = Co, Cu, Rh, Pd, Ag, Ir, Pt, Au) are examined through the self consistent ab-initio scheme depending on the DFT replication. The main purpose of this study is to comprehend several different crucial characteristics of these compounds, including their crystal phase, stability manner, bulk features, band configuration, dielectric, conductivity as well as thermal features. Good accordance in the structural analysis of superconducting materials LaM2Si2 (M = Co, Cu, Rh, Pd, Ag, Ir, Pt, Au) has been observed between the optimized and synthesized lattice parameters. The phonon dispersion curve indicates that the compounds LaCo2Si2, LaCu2Si2, LaRh2Si2, LaPd2Si2, and LaIr2Si2 are dynamically stable, but LaAg2Si2, LaPt2Si2, and LaAu2Si2 are dynamically unstable in nature. Mechanical crystal constancy of the selected materials is verified from the investigated elastic constants. Ductility behaviors of these compounds are ensured by the values of Pugh's and Poisson's ratios. High Young's modulus of LaIr2Si2 ensured its elevated hardness along with huge melting temperature compared than other phases. Anisotropic character of these materials can be ensured through the calculations of elastic anisotropy. The electrical properties of the superconducting LaM2Si2 (M = Co, Cu, Rh, Pd, Ag, Ir, Pt, Au) compounds were also studied in details. Metallic character of the selected solids is observed through the investigation of DOS and band structure calculations. The investigated dielectric function, conductivity, and absorption also reflect the conductive behavior of superconducting LaM2Si2 (M = Co, Cu, Rh, Pd, Ag, Ir, Pt, Au) materials. The optical phenomena ensured their huge absorption as well as optical conductive nature at the site of ultraviolet energy region. Moreover, high reflectivity in the UV region makes these superconductors good solar reflectors for this energy site. Very low minimum thermal conductivity of these compounds especially of LaPt2Si2 and LaAu2Si2 makes them useful and fascinating for thermal barrier coating (TBC) materials.

Fluorescence vs. Phosphorescence: Which Scenario Is Preferable in Au(I) Complexes with Benzothiadiazoles?

The photoluminescence of Au(I) complexes is generally characterized by long radiative lifetimes owing to the large spin-orbital coupling constant of the Au(I) ion. Herein, we report three brightly emissive Au(I) coordination compounds, 1, 2a, and 2b, that reveal unexpectedly short emission lifetimes of 10-20 ns. Polymorphs 2a and 2b exclusively exhibit fluorescence, which is quite rare for Au(I) compounds, while compound 1 reveals fluorescence as the major radiative pathway, and a minor contribution of a microsecond-scale component. The fluorescent behaviour for 1-2 is rationalized by means of quantum chemical (TD)-DFT calculations, which reveal the following: (1) S0-S1 and S0-T1 transitions mainly exhibit an intraligand nature. (2) The calculated spin-orbital coupling (SOC) between the states is small, which is a consequence of overall small metal contribution to the frontier orbitals. (3) The T1 state features much lower energy than the S1 state (by ca. 7000 cm-1), which hinders the SOC between the states. Thus, the S1 state decays in the form of fluorescence, rather than couples with T1. In the specific case of complex 1, the potential energy surfaces for the S1 and T2 states intersect, while the vibrationally resolved S1-S0 and T2-S0 calculated radiative transitions show substantial overlap. Thus, the microsecond-scale component for complex 1 can stem from the coupling between the S1 and T2 states.

Gold–Rare-Metal Mineralization of the Mokrundya Placer Deposit in Arctic Siberia, Republic of Sakha (Yakutia)

Abstract —The Mokrundya alluvial-placer gold deposit is located in the Verkhoyansk–Kolyma folded region, within the Tuguchak ore–placer cluster. The authors used ore and scanning electron microscopy and chemical–analytical methods to study the typomorphic and mineralogic–geochemical features of gold, minerals of the heavy fraction of the placer, and ore mineralization of the dolerite dike complex stripped in the placer bedrock. Stages of development of the ore-forming system in dolerites have been established. The main productive periods with native gold are associated with the postmagmatic stages: (a) early arsenopyrite–polysulfide stage and (b) gold–bismuth–telluride stage. The latter is composed of bismuth tellurides and sulfotellurides, native gold, bismuth, maldonite AuBi2, and complex Au and Bi intermetallic compounds. The authors hypothesize the sources of placer gold in the alluvial deposits. One of them is the ore mineralization of the dolerite dike complex, and the other is associated with mineralized zones of the Gematitovoe skarn–hydrothermal ore occurrence in the upper reaches of the Mokrundya Stream.

2-D Molecular Alloy Ru-M (M = Cu, Ag, and Au) Carbonyl Clusters: Synthesis, Molecular Structure, Catalysis, and Computational Studies.

The reactions of [HRu3(CO)11]− (1) with M(I) (M = Cu, Ag, and Au) compounds such as [Cu(CH3CN)4][BF4], AgNO3, and Au(Et2S)Cl afford the 2-D molecular alloy clusters [CuRu6(CO)22]− (2), [AgRu6(CO)22]− (3), and [AuRu5(CO)19]− (4), respectively. The reactions of 2–4 with PPh3 result in mixtures of products, among which [Cu2Ru8(CO)26]2– (5), Ru4(CO)12(CuPPh3)4 (6), Ru4(CO)12(AgPPh3)4 (7), Ru(CO)3(PPh3)2 (8), and HRu3(OH)(CO)7(PPh3)3 (9) have been isolated and characterized. The molecular structures of 2–6 and 9 have been determined by single-crystal X-ray diffraction. The metal–metal bonding within 2–5 has been computationally investigated by density functional theory methods. In addition, the [NEt4]+ salts of 2–4 have been tested as catalyst precursors for transfer hydrogenation on the model substrate 4-fluoroacetophenone using iPrOH as a solvent and a hydrogen source.

Ab initio study of the structural stability and Dirac fermion behaviour in A3B (A = Cr, Mo, W; B = Al, Ga, In, Si, Ge, Sn, Be) and W3M, M = Ru, Ta, Re, Os, Ir, Au compounds

We study the structural stability and electronic properties of A3B (A = Cr, Mo, and W; B = Al, Ga, In, Si, Ge, Sn, and Be) compounds using ab initio pseudopotential method with Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) for the exchange-correlation functional. It is found that Cr3Be, Cr3Al, Cr3Ga, Cr3Si, Cr3Ge, Mo3Be, Mo3Al, Mo3Ga, Mo3Si, Mo3Ge, and W3Al compounds favor the A15 phase with an exothermic formation energy. In some other cases, the A15 phase has the lowest energy, but the formation energy is endothermic. The stability of these compounds remains unaffected after considering spin-orbit coupling. The charge transfer, electronic density of states, and band structure in each case have been analyzed. The Bader charge analysis shows a large variation in the electronic charge on A atoms. Further we have studied the stability of A15 phase of W3M compounds with M, a transition metal such as Ru, Ta, Re, Os, Ir, and also Au, some of which have recently attracted attention for spintronics applications. A comparison of the results and the occurrence of Dirac fermion behavior in β-W as well as the effects due to the compound formation and spin-orbit coupling have been discussed.

Commercial Gold Complexes Supported on Functionalised Carbon Materials as Efficient Catalysts for the Direct Oxidation of Ethane to Acetic Acid

The single-pot efficient oxidation of ethane to acetic acid catalysed by Au(I) or Au(III) compounds, chlorotriphenylphosphinegold(I) (1), chlorotrimethylphosphinegold(I) (2), 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidenegold(I) chloride (3), dichloro(2-pyridinecarboxylato)gold(III) (4), homogenous and supported on different carbon materials: activated carbon (AC), multi-walled carbon nanotubes (CNT) and carbon xerogel (CX), oxidised with nitric acid followed by treatment with NaOH (-ox-Na), is reported. The reactions were performed in water/acetonitrile. The materials were selective for the production of acetic acid, with no trace of by-products being detected. The best homogenous catalysts were complexes 2 and 3 which showed the highest ethane conversion and an acetic acid yield of ca. 21%, followed by 4 and 1. The heterogenised materials showed much better activity than the homogenous counterparts, with acetic acid yields up to 41.4% for 4@CNT-ox-Na, and remarkable selectivity (with acetic acid being the only product detected). The heterogenised catalysts with the best results were reused up to five cycles, with no significant loss of activity, and maintaining high selectivity for acetic acid. 4@CNT-ox-Na showed not only the best catalytic activity but also the best stability during the recycling runs.

Gold (III) Derivatives in Colon Cancer Treatment.

Cancer is one of the leading causes of morbidity and mortality worldwide. Colorectal cancer (CRC) is the third most frequently diagnosed cancer in men and the second in women. Standard patterns of antitumor therapy, including cisplatin, are ineffective due to their lack of specificity for tumor cells, development of drug resistance, and severe side effects. For this reason, new methods and strategies for CRC treatment are urgently needed. Current research includes novel platinum (Pt)- and other metal-based drugs such as gold (Au), silver (Ag), iridium (Ir), or ruthenium (Ru). Au(III) compounds are promising drug candidates for CRC treatment due to their structural similarity to Pt(II). Their advantage is their relatively good solubility in water, but their disadvantage is an unsatisfactory stability under physiological conditions. Due to these limitations, work is still underway to improve the formula of Au(III) complexes by combining with various types of ligands capable of stabilizing the Au(III) cation and preventing its reduction under physiological conditions. This review summarizes the achievements in the field of stable Au(III) complexes with potential cytotoxic activity restricted to cancer cells. Moreover, it has been shown that not nucleic acids but various protein structures such as thioredoxin reductase (TrxR) mediate the antitumor effects of Au derivatives. The state of the art of the in vivo studies so far conducted is also described.

Breast Cancer Treatment: The Case of Gold(I)-Based Compounds as a Promising Class of Bioactive Molecules.

Breast cancers (BCs) may present dramatic diagnoses, both for ineffective therapies and for the limited outcomes in terms of lifespan. For these types of tumors, the search for new drugs is a primary necessity. It is widely recognized that gold compounds are highly active and extremely potent as anticancer agents against many cancer cell lines. The presence of the metal plays an essential role in the activation of the cytotoxicity of these coordination compounds, whose activity, if restricted to the ligands alone, would be non-existent. On the other hand, gold exhibits a complex biochemistry, substantially variable depending on the chemical environments around the central metal. In this review, the scientific findings of the last 6–7 years on two classes of gold(I) compounds, containing phosphane or carbene ligands, are reviewed. In addition to this class of Au(I) compounds, the recent developments in the application of Auranofin in regards to BCs are reported. Auranofin is a triethylphosphine-thiosugar compound that, being a drug approved by the FDA—therefore extensively studied—is an interesting lead gold compound and a good comparison to understand the activities of structurally related Au(I) compounds.

Gold Compounds Inhibit the Ca2+-ATPase Activity of Brain PMCA and Human Neuroblastoma SH-SY5Y Cells and Decrease Cell Viability

Plasma membrane calcium ATPases (PMCA) are key proteins in the maintenance of calcium (Ca2+) homeostasis. Dysregulation of PMCA function is associated with several human pathologies, including neurodegenerative diseases, and, therefore, these proteins are potential drug targets to counteract those diseases. Gold compounds, namely of Au(I), are well-known for their therapeutic use in rheumatoid arthritis and other diseases for centuries. Herein, we report the ability of dichloro(2-pyridinecarboxylate)gold(III) (1), chlorotrimethylphosphinegold(I) (2), 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidenegold(I) chloride (3), and chlorotriphenylphosphinegold(I) (4) compounds to interfere with the Ca2+-ATPase activity of pig brain purified PMCA and with membranes from SH-SY5Y neuroblastoma cell cultures. The Au(III) compound (1) inhibits PMCA activity with the IC50 value of 4.9 µM, while Au(I) compounds (2, 3, and 4) inhibit the protein activity with IC50 values of 2.8, 21, and 0.9 µM, respectively. Regarding the native substrate MgATP, gold compounds 1 and 4 showed a non-competitive type of inhibition, whereas compounds 2 and 3 showed a mixed type of inhibition. All gold complexes showed cytotoxic effects on human neuroblastoma SH-SY5Y cells, although compounds 1 and 3 were more cytotoxic than compounds 2 and 4. In summary, this work shows that both Au (I and III) compounds are high-affinity inhibitors of the Ca2+-ATPase activity in purified PMCA fractions and in membranes from SH-SY5Y human neuroblastoma cells. Additionally, they exert strong cytotoxic effects.

Long-bonding and bonding nature in noble gas insertion compounds MNgBY of transition metal-boron bond

The nature of inert gas bonding has always been an important topic. The bonds of noble gases cover the entire range of chemical bonds, from the weakest van der Waals forces, to non-covalent interactions, and to covalent bonds. Two types of methods were used to investigate the properties of chemical bonds in the inert gas inserted compound MNgBY with the transition metal M = Cu/Ag/Au and substituents Y = O/S/NH, one based on orbital analysis and the other based on electron density analysis. The NBO/NRT analysis shows that in these compounds there exists long-bonding striding the noble gas between the transitional metal and boron, similar to the noble gas insertion compounds HNgX of hydrohalide, and so a three-center four-electron bond exists among the M-Ng-B part. The electron density analyses show that the M-Ng bond between the metal Cu/Ag/Au and noble gas and the Ng-B bond in the Cu/Ag compounds are partial covalent but the Ng-B bond in Au compounds is a typical covalent bond. The large relativistic effects of Au cause the bonds in Au compounds shorter and stronger than the bonds in Ag/Cu compounds. The properties of the M-Ng and Ng-B bonds are not affected by substituents Y, but the bond lengths are sensitive to substituents.

Biosynthesis of gold nanoparticles for the treatment of osteoarthritis alone or in combination with Diacerein® in a rat model.

Gold (Au) compounds were used as an effective therapeutic agent for various inflammatory diseases; however, the use of Au compounds becomes limited because of its association with several side effects. Hence, gold nanoparticles (AuNPs) were developed as a new option for the medical proposes. However, the safety evaluation of gold nanoparticles (AuNPs) in osteoarthritis (OA) treatment remains vague. This study aimed to biosynthesize, characterize and evaluate the therapeutic effects of biosynthesized AuNPs and/or Diacerein® (DIA) in experimental OA. OA was induced by a single injection of monosodium iodoacetate (3mg/joint) in the intra-articular knee of female rats. Normal rats (N-rats) and OA-rats were treated orally for 5weeks as follow: untreated N-rats; untreated OA-rats; N-rats received DIA (50mg/kg b.w); N-rats received AuNPs (30μg/kg b.w.); N-rats received AuNPs plus DIA; OA-rats received DIA; OA-rats received AuNPs, and OA-rats received AuNPs plus DIA. Blood, knee cartilage, liver and kidney samples were collected for biochemical and histological analysis. The synthesized AuNPs were nearly spherical with average size of 20nm and zeta potential of 33mV. AuNPs and DIA induced a significant improvement in serum inflammatory cytokines, biochemical parameters, estrogen level, hepatic and renal oxidative markers, hepatic DNA fragmentation, genomic template stability and cartilage joint histology of OA-rats. AuNPs were more effective than DIA and the combined treatment was more effective than the single treatment. It could be concluded that AuNPs are promising for the treatment of OA alone or in combination with DIA.

The Beauty of Gold: Knowledge of Mechanisms Leads to Different Applications of Organogold Compounds in Medicine and Catalysis

This review is aimed at providing a concise overview of the results obtained by our group in the field of organometallic chemistry of gold. Therefore, a selection of examples amongst the most extensively explored families of bioactive gold complexes — Au(I) N-heterocyclic carbenes and cyclometalated Au(III) compounds — is presented. Insights into the bio-inorganic mechanisms of reactivity of organogold compounds obtained by an integrated investigational approach, and knowledge of structure-activity relationships are discussed also in relation to novel applications of gold-based catalysts and metal-mediated transformations in aqueous environment.

Rollover Cyclometalation vs Nitrogen Coordination in Tetrapyridyl Anticancer Gold(III) Complexes: Effect on Protein Interaction and Toxicity.

In this work, a pair of gold(III) complexes derived from the analogous tetrapyridyl ligands H2biqbpy1 and H2biqbpy2 was prepared: the rollover, bis-cyclometalated [Au(biqbpy1)Cl ([1]Cl) and its isomer [Au(biqbpy2)Cl ([2]Cl). In [1]+, two pyridyl rings coordinate to the metal via a Au–C bond (C∧N∧N∧C coordination) and the two noncoordinated amine bridges of the ligand remain protonated, while in [2]+ all four pyridyl rings of the ligand coordinate to the metal via a Au–N bond (N∧N∧N∧N coordination), but both amine bridges are deprotonated. As a result, both complexes are monocationic, which allowed comparison of the sole effect of cyclometalation on the chemistry, protein interaction, and anticancer properties of the gold(III) compounds. Due to their identical monocationic charge and similar molecular shape, both complexes [1]Cl and [2]Cl displaced reference radioligand [3H]dofetilide equally well from cell membranes expressing the Kv11.1 (hERG) potassium channel, and more so than the tetrapyridyl ligands H2biqbpy1 and H2biqbpy2. By contrast, cyclometalation rendered [1]Cl coordinatively stable in the presence of biological thiols, while [2]Cl was reduced by a millimolar concentration of glutathione into metastable Au(I) species releasing the free ligand H2biqbpy2 and TrxR-inhibiting Au+ ions. The redox stability of [1]Cl dramatically decreased its thioredoxin reductase (TrxR) inhibition properties, compared to [2]Cl. On the other hand, unlike [2]Cl, [1]Cl aggregated into nanoparticles in FCS-containing medium, which resulted in much more efficient gold cellular uptake. [1]Cl had much more selective anticancer properties than [2]Cl and cisplatin, as it was almost 10 times more cytotoxic to human cancer cells (A549, A431, A375, and MCF7) than to noncancerous cells (MRC5). Mechanistic studies highlight the strikingly different mode of action of the two compounds: while for [1]Cl high gold cellular uptake, nuclear DNA damage, and interaction with hERG may contribute to cell killing, for [2]Cl extracellular reduction released TrxR-inhibiting Au+ ions that were taken up in minute amounts in the cytosol, and a toxic tetrapyridyl ligand also capable of binding to hERG. These results demonstrate that bis-cyclometalation is an appealing method to improve the redox stability of Au(III) compounds and to develop gold-based cytotoxic compounds that do not rely on TrxR inhibition to kill cancer cells.

Medicinal Au(I) compounds targeting urease as prospective antimicrobial agents: unveiling the structural basis for enzyme inhibition.

A few gold compounds were recently found to show antimicrobial properties in vitro, holding great promise for the discovery of new drugs to overcome antibiotic resistance. Here, the inhibition of the bacterial virulence factor urease by four Au(I)-compounds, namely Au(PEt3)Cl, Au(PEt3)Br, Au(PEt3)I and [Au(PEt3)2]Cl, obtained from the antiarthritic Au(I)-drug Auranofin and earlier reported to act as antimicrobials, is investigated. The three monophosphino Au(I) complexes showed IC50 values in the 30-100 nM range, while the diphosphino Au(I) complex, though being less active, still showed a IC50 value of 7 μM. The structural basis for this inhibition was provided by solving the crystal structures of urease co-crystallized with Au(PEt3)I and [Au(PEt3)2]Cl: at least two Au(I) ions bind the enzyme in a flap domain involved in the catalysis, thus obliterating enzyme activity. Peculiar changes observed in the two structures reveal implications for the mechanism of soft metal binding and enzyme inactivation.

Pressure-induced Na–Au compounds with novel structural units and unique charge transfer

The exploration of novel intermetallic compounds is of great significance for basic research and practical application. Considering the interesting and diverse attributes of Na and Au, their large electronegative difference, and the unresolved high-pressure Na-Au structures, first-principles swarm-intelligence structural search calculations are employed to explore the potential Na-Au compounds at high pressures. Besides reproducing the known Na-Au compounds, eleven new phases are disclosed, exhibiting several unprecedented Au atomic arrangements, such as rectangular ladder, layer formed by edge-sharing squares, hexahedron framework, and diamond-like skeleton, enriching the understanding of Au chemistry. Moreover, the coordination number of Au can be effectively modulated by controlling Na composition. In the Na-rich compounds (Na4Au, Na5Au, and Na6Au), Au shows a formal charge beyond -2, acting as a 6p-block element, originating from pressure-induced unusual Na 3s or 3p → Au 6p charge transfer. These compounds are metallic, but not superconductive. Moreover, the good agreement between the experimental XRD patterns and the simulated ones allows us to assign the predicted P6/mmm Na2Au and Fm3[combining macron]m Na3Au as the experimental structures at 59.6 GPa. Our work indicates that the modulation of pressure and chemical composition is a useful way to stabilize novel intermetallic compounds.