Thiolate Complexes Research Articles

Silica gels doped with gold nanoparticles and gold thiolate complexes: The effect of heating and preparation conditions

A novel sol-gel strategy for the preparation of silica nanocomposites, containing gold nanoparticles (AuNPs), Au(I)-thiolate complexes (Au-SC12) or both disperse phases is demonstrated. The color of the species depends on the size and surrounding of the AuNPs. The nanocomposites obtained are characterized with UV/Vis reflectance spectroscopy, X-Ray diffraction, TEM / EDAX and thermal conductivity measurements. An analysis of the UV/VIS spectra, based on Mie's theory, suggests the presence of 5 - 30 nm AuNPs with different chemical surroundings. Heating of the nanocomposites at 700 °C leads to red or violet colored SiO2:AuNPs powders. The thermal conductivity of the nanocomposites is about 0.05–0.07 W/m.K, depending on sintering and chemical composition. A discussion about the microstructure of the composites is also presented.

Influence of the second coordination sphere on O2 activation by a nonheme iron(II) thiolate complex

Influence of the second coordination sphere on O2 activation by a nonheme iron(II) thiolate complex

Flash Communication: Synthesis and Characterization of an Iron(V) Thiolate Complex

Flash Communication: Synthesis and Characterization of an Iron(V) Thiolate Complex

Chemistry of Antimony in Radiopharmaceutical Development: Unlocking the Theranostic Potential of Sb Isotopes.

Antimony-119 (119Sb) holds promise for radiopharmaceutical therapy (RPT), emitting short-range Auger and conversion electrons that can deliver cytotoxic radiation on a cellular level. While it has high promise theoretically, experimental validation is necessary for 119Sb in vivo applications. Current 119Sb production and separation methods face robustness and compatibility challenges in radiopharmaceutical synthesis. Limited progress in chelator development hampers targeted experiments with 119Sb. This review compiles literature on the toxicological, biodistribution and redox properties of Sb, along with existing Sb complexes, evaluating their suitability for radiopharmaceuticals. Sb(III) is suggested as the preferred oxidation state for radiopharmaceutical elaboration due to its stability in vivo and lack of skeletal uptake. While Sb complexes with both hard and soft donor atoms can be achieved, Sb thiol complexes offer enhanced stability and compatibility with the desired Sb(III) oxidation state. For 119Sb to find application in RPT, scientists need to make discoveries and advancements in the areas of isotope production, and radiometal chelation. This review aims to guide future research towards harnessing the therapeutic potential of 119Sb in RPT.

Comparative Electrocatalysis of Hydrogen Production and Oxidation: Technetium versus Rhenium Tris(thiolate) Complexes

AbstractThe development of an efficient catalyst that can selectively activate and generate hydrogen molecules is in urgent demand. Inspired by the 5d rhenium‐tris(thiolate) complex that is capable of catalytically producing and oxidizing H2, the mechanisms of electrocatalytic H2 oxidation (HOR) and evolution (HER) catalyzed by the 4d technetium‐tri(thiolate) analogs, and [TcL3] (L = diphenylphosphinobenzenethiolate, a noninnocent ligand), were investigated by DFT calculations, aiming at elucidating the role of the metal in metal‐ligand cooperativity. DFT calculations anticipate high reactivity in both HOR and HER for [TcL3] beyond that of its Re counterparts. Substituting the Re metal for Tc in metal‐tris(thiolate) complexes results in a greater thiyl‐radical character in the Tc complex compared to that in Re. Even when both complexes evolve H2 with similar [ECEC] mechanisms, the proton relays behave with a distinct disparity, featuring the S ligand in the Tc species as compared to the metal‐hydride in Re. The HOR mechanism also bifurcates as [TcL3]2+ is predicted to mainly occur via the ligand‐based pathway, in contrast to the predominant metal and ligand‐based reactivity for Re. This study established the role of the metal in HER and HOR while emphasizing the utility of such metal‐DPPBT cooperativity in the catalytic process.

Rhenium(V) Tris(pyrazolyl)borate Thiolate Complex with the Disulfide Bridging Ligand: Synthesis and Structure

The reaction of TpReOCl(StBu) (Tp = tris(pyrazolyl)borate anion) with sodium disulfide in dimethoxyethane affords the new binuclear rhenium complex [TpReO(μ-StBu)]2(μ-S2) (I). Complex I can also be synthesized by the reaction of TpReO(StBu)2 with a suspension of manganese(II) bromide in toluene accompanied by the dealkylation of one of the ligands to form one more new complex [TpReO]2(μ-S2)(μ-S) (II) containing the bridging sulfide and disulfide ligands. The structures of two crystalline solvates of complex I with dichloromethane containing the molecules with different conformations of the Re2S2 fragment (Ia and Ib) and complex II are studied by X-ray diffraction (XRD) (CIF files ССDC nos. 2262677, 2262678, and 2267423 for Ia, Ib, and II, respectively).

Synthesis, Characterization, and Reactivity of a Synthetic End-On Cobalt(II) Alkyl Persulfide Complex as a Model Platform for Thiolate Persulfidation.

Persulfides (RSS-) are ubiquitous source of sulfides (S2-) in biology, and interactions between RSS- and bioinorganic metal centers play critical roles in biological hydrogen sulfide (H2S) biogenesis, signaling, and catabolism. Here, we report the use of contact-ion stabilized [Na(15-crown-5)][tBuSS] (1) as a simple synthon to access rare metal alkyl persulfide complexes and to investigate the reactivity of RSS- with transition metal centers to provide insights into metal thiolate persulfidation, including the fundamental difference between alkyl persulfides and alkyl thiolates. Reaction of 1 with [CoII(TPA)(OTf)]+ afforded the η1-alkyl persulfide complex [CoII(TPA)(SStBu)]+ (2), which was characterized by X-ray crystallography, UV-vis spectroscopy, and Raman spectroscopy. RSS- coordination to the Lewis acidic Co2+ center provided additional stability to the S-S bond, as evidenced by a significant increase in the Raman stretching frequency for 2 (vS-S = 522 cm-1, ΔvS-S = 66 cm-1). The effect of persulfidation on metal center redox potentials was further elucidated using cyclic voltammetry, in which the Co2+ → Co3+ oxidation potential of 2 (Ep,a = +89 mV vs SCE) is lowered by nearly 700 mV when compared to the corresponding thiolate complex [CoII(TPA)(StBu)]+ (3) (Ep,a = +818 mV vs SCE), despite persulfidation being generally seen as an oxidative post-translational modification. The reactivity of 2 toward reducing agents including PPh3, BH4-, and biologically relevant thiol reductant DTT led to different S2- output pathways, including formation of a dinuclear 2Co-2SH complex [CoII2(TPA)2(μ2-SH)2]2+(4).

Platinum(II) and palladium(II) thiolate complexes; synthesis, characterization, crystal structure, DFT, Hirshfeld surface analysis and anticancer studies

Platinum(II) and palladium(II) thiolate complexes; synthesis, characterization, crystal structure, DFT, Hirshfeld surface analysis and anticancer studies

Syntheses, structures, photoelectricity and photocatalysis of Cu(I) iodide hybrids and thiolate derived from dithiodipyridine

Iodocuprate hybrids {[(4,4′-dtdpy)2Cu2I2]·DMA}n (4,4′-dtdpy = 4,4′-dithiodipyridine; DMA = N,N-dimethylacetamide) (1) and [(2,2′-dtdpy)Cu2I2]2 (2,2′-dtdpy = 2,2′-dithiodipyridine) (2) were prepared by reacting CuI and KI using 4,4′-dtdpy and 2,2′-dtdpy as SDAs, respectively, at room temperature. The Cu2I2 aggregates were joined by a μ-4,4′-dtdpy bridging ligand with N-donor atom, and by a 2,2′-dtdpy chelating ligand with N- and S-donor atoms to form a 1-D polymeric complex {[(4,4′-dtdpy)2Cu2I2]·DMA}n and a tetranuclear complex [(2,2′-dtdpy)Cu2I2]2, respectively. The reaction CuI, KI and 2,2′-dtdpy in CH3OH solvent under solvothermal conditions formed a polymeric iodocuprate hybrid [(mmtpy)(Cu2I3)]n (mmtpy+ = 1-methyl-2-(methylthio)pyridinium) (3). 2,2′-dtdpy was converted in situ to the mmtpy+ cation via cleavage of the SS bond and methylation of the N and S atoms in the solvothermal reaction. In compound 3, tetrahedral CuI4 units are connected into a 1-D [Cu2I3]nn− chain by edge- and face-sharing. In the same solvothermal reaction in DMF, the SS bond of 2,2′-dtdpy was cleaved to form a mtpy– anion. The mtpy– anion coordinated to Cu+ ions as a bidentate ligand with N and S-donor atoms to form a hexanuclear thiolate complex [Cu6(mtpy)6] (Hmtpy = 2-mercaptopyridine) (4). A pseudohexagonal prismatic Cu6S6 core is formed in 4. Compounds 1–4 showed strong photocurrent responses with steady current densities in the range of 0.33–0.79 μA·cm−2. Compounds 1–4 are catalytically active in the photodegradation of MB with degradation ratios of 80.5 %, 90.3 %, 100 %, and 84.6 %, respectively, after 120 min of light irradiation.

Ligand Basicity and Chelate Effects on Sulfur Insertion vs. Sulfur Reduction by Zinc Thiolate Complexes.

4- and 5-coordinate zinc thiolate complexes supported either by bis(carboxamide)pyridine frameworks or by substituted tris(pyrazolyl)borate ligands react with elemental sulfur (S8) following two distinct pathways. Some zinc thiolate moieties insert sulfur atoms to form zinc polysulfanide complexes, while others reduce sulfur and oxidize the thiolate. Here, we compare the effects of ligand electronics, strain, and sterics for selecting the respective reaction pathway. These results show that chelating and electron-deficient thiolate ligands better stabilize persistent zinc-bound polysulfanide species.

Fe/Thiol Cooperative Hydrogen Atom Transfer Olefin Hydrogenation: Mechanistic Insights That Inform Enantioselective Catalysis.

Asymmetric hydrogenation of activated olefins using transition metal catalysis is a powerful tool for the synthesis of complex molecules, but traditional metal catalysts have difficulty with enantioselective reduction of electron-neutral, electron-rich, and minimally functionalized olefins. Hydrogenation based on radical, metal-catalyzed hydrogen atom transfer (mHAT) mechanisms offers an outstanding opportunity to overcome these difficulties, enabling the mild reduction of these challenging olefins with selectivity that is complementary to traditional hydrogenations with H2. Further, mHAT presents an opportunity for asymmetric induction through cooperative hydrogen atom transfer (cHAT) using chiral thiols. Here, we report insights from a mechanistic study of an iron-catalyzed achiral cHAT reaction and leverage these insights to deliver stereocontrol from chiral thiols. Kinetic analysis and variation of silane structure point to the transfer of hydride from silane to iron as the likely rate-limiting step. The data indicate that the selectivity-determining step is quenching of the alkyl radical by thiol, which becomes a more potent H atom donor when coordinated to iron(II). The resulting iron(III)-thiolate complex is in equilibrium with other iron species, including FeII(acac)2, which is shown to be the predominant off-cycle species. The enantiodetermining nature of the thiol trapping step enables enantioselective net hydrogenation of olefins through cHAT using a commercially available glucose-derived thiol catalyst with up to 80:20 enantiomeric ratio. To the best of our knowledge, this is the first demonstration of asymmetric hydrogenation via iron-catalyzed mHAT. These findings advance our understanding of cooperative radical catalysis and act as a proof of principle for the development of enantioselective iron-catalyzed mHAT reactions.

Bimetallic Perthiocarbonate Complexes of Cobalt: Synthesis, Structure and Bonding.

The syntheses and structural elucidation of bimetallic thiolate complexes of early and late transition metals are described. Thermolysis of the bimetallic hydridoborate species [{Cp*CoPh}{µ-TePh}{µ-TeBH3-ĸ2Te,H}{Cp*Co}] (Cp* = ɳ5-C5Me5) (1) in the presence of CS2 afforded the bimetallic perthiocarbonate complex [(Cp*Co)2(μ-CS4-κ1S:κ2S')(μ-S2-κ2S″:κ1S‴)] (2) and the dithiolene complex [(Cp*Co)(μ-C3S5-κ1S,S'] (3). Complex 2 contains a four-membered metallaheterocycle (Co2S2) comprising a perthiocarbonate [CS4]2- unit and a disulfide [S2]2- unit, attached opposite to each other. Complex 2 was characterized by employing different multinuclear NMR, infrared spectroscopy, mass spectrometry, and single-crystal X-ray diffraction studies. Preliminary studies show that [Cp*VCl2]3 (4) with an intermediate generated from CS2 and [LiBH4·THF] yielded thiolate species, albeit different from the cobalt system. Furthermore, a computational analysis was performed to provide insight into the bonding of this bimetallic perthiocarbonate complex.

A high-efficiency photocatalytic hydrogen evolution system based on nickel-quinoxaline dithiolate complexes and water-soluble CdSe quantum dots

Photocatalytic water splitting of water for hydrogen evolution is one of the effective methods to obtain clean hydrogen energy. In the present work, the following materials were synthesized: two nickel quinoxaline thiolate complexes [NBu4]2 [Ni(qdt)2] (1, Bu = n-butyl, qdt = quinoxaline-dithiol), [NBu4]2 [Ni(qdt)2(NO2)2] (2) and water-soluble MPA-CdSe quantum dots (MPA-CdSe QDs, MPA = 3-mercaptopropionic acid). Subsequently, an efficient three-component photocatalytic hybrid system for hydrogen evolution was developed and tested under visible light irradiation, in which one of the target complex 1 or 2 was used as the catalyst, triethylamine (TEA) was used as the sacrificial electron donor, and MPA-CdSe QDs were used as the light harvesting reagent. The turnover numbers (TON) for H2 evolution of 8974 (vs. complex 1) and 6532 (vs. complex 2) were obtained under the optimal conditions with TEA concentration of 5 %, pH = 12, and concentration of complex 1 or 2 of 1 × 10−5 mol L−1 after 13 h of irradiation (λ > 420 nm) in pure water. The mechanism investigation indicated that critical steps of hydrogen production was formation of hydride intermediates Ni(II)-H and Ni(I)-H spices, followed by the reaction of two Ni(II)-H or Ni(I)-H species with protons generating H2 molecules and regenerating the catalyst Ni(II).

On the geometry dependence of the nuclear magnetic resonance chemical shift of mercury in thiolate complexes: A relativistic density functional theory study.

Thiolate containing mercury(II) complexes of the general formula [Hg(SR) ] have been of great interest since the toxicity of mercury was recognized. 199Hg nuclear magnetic resonance spectroscopy (NMR) is a powerful tool for characterization of mercury complexes. In this work, the Hg shielding constants in a series of [Hg(SR) ] complexes are therefore investigated computationally with particular emphasis on their geometry dependence. Geometry optimizations and NMR chemical shift calculations are performed at the density functional theory (DFT) level with both the zeroth-order regular approximation (ZORA) and four-component relativistic methods. The four exchange-correlation (XC) functionals PBE0, PBE, B3LYP, and BLYP are used in combination with either Dyall's Gaussian-type (GTO) or Slater-type orbitals (STOs) basis sets. Comparing ZORA and four-component calculations, one observes that the calculated shielding constants for a given molecular geometry have a constant difference of 1070 ppm. This confirms that ZORA is an acceptable relativistic method to compute NMR chemical shifts. The combinations of four-component/PBE0/v3z and ZORA/PBE0/QZ4P are applied to explore the geometry dependence of the isotropic shielding. For a given coordination number, the distance between mercury and sulfur is the key factor affecting the shielding constant, while changes in bond and dihedral angles and even different side groups have relatively little impact.

Impact of light on protective fractions of Cu in white wine: Influence of oxygen and bottle colour

Cu(II)-organic acid (fraction I) and Cu(I)-thiol (fraction II) complexes can suppress sulfhydryl off-aromas in wine. This study investigated the impact of light exposure on the protective fractions of Cu of bottled white wine. Fluorescent light-exposed Chardonnay with two initial concentrations of dissolved oxygen (0.5 and 10 mg/L) was stored in different coloured bottles and concentrations of Cu fractions and riboflavin, a photo-initiator at 370–440 nm, were measured during 110 days storage. Light-exposed wines with lower oxygen concentrations resulted in a 100-fold decrease in the Cu fraction I half-life, and a 60-fold decrease for Cu fractions I and II combined. The half-life for Cu fraction I decay during light exposure was extended 30-fold with the use of brown compared to flint glass. Light exposure can rapidly exhaust the protective Cu fractions in wine, and bottles with less light transmission below 440 nm can slow this loss.

Unravelling the role of precursors phosphine`s features in governing the reactivity of [MCl2(P-P)] (M = Pd, Pt) towards formation of thiolate complexes via S−S and S−C bond cleavage

Group 10 thiolate complexes have been in the quest zone of research due to pertinent catalytic potential. The present work unravels the role of precursor phosphine`s feature in their reactivity towards 4,6-dimethylpyrimidine-2-thiol and subsequent thiolate complex. Synthesized thiolate complexes were thoroughly characterized using elemental analyses, NMR (1H, 13C{1H}, 31P{1H}), UV–Vis spectroscopy and Single Crystal X-ray diffraction analyses. Treatment of [MCl2(PPh3)2] (M = Pd, Pt) with two equivalents of NaSC4H(4,6-Me)N2 resulted in chelated [Pd{κ-S, κ-N: SC4H(4,6-Me)2N2}{SC4H(4,6-Me)2N2}(PPh3)] (1a) as well as an expected trans compound [Pt{SC4H(4,6-Me)2N2}2(PPh3)2] (1b). A similar reaction with the chelating phosphine ‘dppm’ (dppm = 1,1-bis(diphenylphosphino)methane) as an ancillary ligand resulted in the serendipitous product of composition [Pd2(µ2-S){SC4H(4,6-Me)2N2}2(µ2-dppm)2] (2a) depending upon competitive cleavage of S-S and S-C bond. The reaction of [PdCl2(dppe)] afforded a cis configured compound [Pd{2-SC4H(4,6-Me)2N2}2(dppe)] (2b). Contrary, the similar reaction of [PdCl2(dppp)] results in removal of ‘dppp’ (1,3-bis(diphenylphosphino)propane) yielding the chelated complex [Pd{κ-S, κ-N: SC4H(4,6-Me)2N2}2] (2c). Above all, the reactivity of 4,6-dimethylpyrimidine-2-thiol significantly differs compared to unsubstituted pyrimidyl, pyridyl analogue which has been attributed to the additional richness of electrons/activation in the ring which in turn facilitates competitive reactivity pattern of S-S and S-C bond. The virtue of such activation can easily be understood by the isolation of complex [Pd2(µ2-S){SC4H(4,6-Me)2N2}2(µ2-dppm)2] (2a). Rationalization of results via DFT calculation reveals that projection angle P-M-P (ranging from ∼75 to 92°) driven structural change in the chelating phosphine and associated degree of softness in ligand molecule played a crucial role in governing the resulting product of substitution reaction as dimeric, monomeric and chelated complexes. Thus, projection angle- driven geometrical and electronic structure and variation provide opportunity and direction to efficiently derive biologically as well as academically important complexes.

Surface Nanodroplet‐Confined Engineering of Gold (I) ‐Thiolate Nanostructures

AbstractGold(I)‐thiolate complexes have served as primary building blocks for diverse Au nanostructure synthesis strategies. A delicate approach to characterize and control Au(I)‐thiolate motif formation and assembly on the surface is needed as it can potentially solve challenges associated with utilizing gold nanomaterials in many applications. Here, the controllable generation of flower‐shaped surface gold nanostructures (FSGNs) is demonstrated by manipulating the formation‐assembly process of Au(I)‐dodecanethiolate motifs within nanoscale surface droplets. The morphology and structure of the resulting Au nanostructures are governed by internal convection flows and interfacial energy, modulated by the nanodroplet composition and substrate wettability. The obtained FSGNs are proven to act as versatile scaffolds for the selective generation of Au spiky nanostars. These FSGNs can also be utilized to functionalize nanodroplet‐based reactors, boosting the fluorescent intensity of Nile red (NR) fluorophores and decomposing NR via catalytic reaction. Remarkably, with FSGN functionalized droplets smaller than a radius of 500 nm, the decomposition rate of NR can reach ≈0.01 s−1. These results highlight a miniaturized, controllable, and automated method for the in situ production of 3D gold nanostructures on substrates, offering prospects for fast surface nanostructure fabrication and efficient environmental pollutant treatment.

Noble Metal Nanoparticles with Nanogel Coatings: Coinage Metal Thiolate-Stabilized Glutathione Hydrogel Shells.

Developing biocompatible nanocoatings is crucial for biomedical applications. Noble metal colloidal nanoparticles with biomolecular shells are thought to combine diverse chemical and optothermal functionalities with biocompatibility. Herein, we present nanoparticles with peptide hydrogel shells that feature an unusual combination of properties: the metal core possesses localized plasmon resonance, whereas a few-nanometer-thick shells open opportunities to employ their soft framework for loading and scaffolding. We demonstrate this concept with gold and silver nanoparticles capped by glutathione peptides stacked into parallel β-sheets as they aggregate on the surface. A key role in the formation of the ordered structure is played by coinage metal(I) thiolates, i.e., Ag(I), Cu(I), and Au(I). The shell thickness can be controlled via the concentration of either metal ions or peptides. Theoretical modeling of the shell's molecular structure suggests that the thiolates have a similar conformation for all the metals and that the parallel β-sheet-like structure is a kinetic product of the peptide aggregation. Using third-order nonlinear two-dimensional infrared spectroscopy, we revealed that the ordered secondary structure is similar to the bulk hydrogels of the coinage metal thiolates of glutathione, which also consist of aggregated stacked parallel β-sheets. We expect that nanoparticles with hydrogel shells will be useful additions to the nanomaterial toolbox. The present method of nanogel coating can be applied to arbitrary surfaces where the initial deposition of the seed glutathione monolayer is possible.

Reprocessable and Recyclable Self-Healing Natural Rubber/Carbon Black Composite Based on Metal Thiolate Ionic Network

Reprocessable and recyclable self-healing rubber composites were fabricated by mixing natural rubber (NR) with carbon black (CB) filler in the presence of zinc thiolate (ZT) to form the ionic association in the rubber system. This work investigated and compared the unfilled and natural rubber filled with 5phr of carbon black. The recycling process was repeated three times, and the mechanical performance was measured each time. Tensile strength was increased by more than 430% for unfilled rubber and 520% for NR/5CB composites after the third recycling process. Tear strength was also increased with the number of the recycling process. According to a welding test ability, the developed materials showed potential for repair. Scanning electron micrographs revealed that as the recycling number increased, the white spot of ZT responsible for generating the ionic network reduced as more ZT was converted into Zn2+ salt bonding.

Rhenium(V) Tris(pyrazolyl)borate Thiolate Complex with the Disulfide Bridging Ligand: Synthesis and Structure

Rhenium(V) Tris(pyrazolyl)borate Thiolate Complex with the Disulfide Bridging Ligand: Synthesis and Structure