Thiolate Complexes Research Articles

A facile approach to fabricate room temperature intrinsic self-healing fabrics

Self-healing fabrics have garnered a lot of attention due to their recovering functionality upon damage. This work describes a facile technique for developing a novel self-healing coating with the goal of producing autonomous intrinsic self-healing fabrics that can recover from damage at room temperature without the use of external stimuli. The coating was developed using natural rubber latex (NRL) and consisted of a dynamic reversible metal thiolate ionic network. The formation of the reversible ionic network was assessed by Differential Scanning Calorimetry (DSC), Ultraviolet-visible spectroscopy (UV-vis), Fourier Transform Infrared (FTIR) and zeta potential analysis. Scanning electron microscope (SEM) images revealed that the coating impregnated the fibres of the fabric and improved their structural integrity. The morphology of the punctured area revealed that intermolecular diffusion had occurred during the recovery and the sample had completely healed. The results also showed that the tensile strength, tear strength and puncture strength of the fabric achieved 100% healing efficiency when the damaged fabrics were brought into contact with each other and allowed to be healed at room temperature. This technology is expected to open up a new avenue in the textile industry.

Interaction of the Bipyridyl Gold(III) Complex with Anions of Thiol-Containing Acids in Aqueous Solution

The equilibria of stepwise substitution Au(bipy)+ OH– = Au(bipy)ClOH+ + Cl– and Au(bipy)+ 2OH– = Au(bipy)+ 2Cl– in aqueous solution at T = 25°C and I = 0.2 M (NaCl), log β1 = 9.22, log β2 = 16.61 have been studied. For bipyridyl complexes Au(bipy)(X = Cl, OH) at pH 2.0 and 7.4, redox interactions with anions of thiol-containing acids (glutathione, cysteine, thiomalate) have been studied. In all cases, at the initial stage, a rapid reduction of gold(III) to gold(I) was observed with the simultaneous release of bipyridyl. A detailed analysis of UV spectra showed that the main products of gold(III) reduction are highly stable gold(I) thiolate complexes. The presence of further slower steps depends on the initial ratio of thiol to gold.

Investigation of thiol compounds (L-cysteine, thioacetic acid and ethanethiol) with V(V) and V(IV) using combined spectroscopy and chromatography

The interactions of V(V) and L-cysteine, thioacetic acid and ethanethiol were studied in aqueous solution using chromatographic and spectral analysis. The chromatographic determination of V(V) and V(IV) species in the presence of thiols was enabled by inducing the ligand exchange reaction with EDTA as the competing ligand. Analytical setup allowed investigation of the possible redox and structural transformations of V(V) in the presence of thiols used over a wide pH range. Obtained data strongly suggest that the reduction of V(V) is proton catalyzed in case of L-cysteine and thioacetic acid. In the case of ethanethiol, the reduction did not seem to be proton dependent, as no reduction was observed above pH = 2. Thus, reduction was inhibited by the deprotonation of L-cysteine and thioacetic acid, with L-cysteine being the strongest reducing agent of V(V), followed by thioacetic acid and finally ethanethiol. Apart from structural thiol properties, the reduction reaction seems to be influenced by the aqueous V(V) speciation due to the observed nonlinear kinetics. In the case of all investigated thiols, the formation of V(V)-thioester intermediate species was an essential step for V(V) reduction. The structural properties of the V(IV)-thiol complexes were also found to be pH-dependent.

Theoretical Understanding of Reactions of Rhenium and Ruthenium Tris(thiolate) Complexes with Unsaturated Hydrocarbons: Noninnocent Nature of the Ligand, Mechanism, and Origin of Differential Reactivity

In retrospect to the complexity induced by the noninnocent ligands in identifying the transition metal's oxidation state and correlating the ligand's noninnocence with reactivity, the reactions of alkene/alkyne addition to rhenium/ruthenium tris(thiolate) complexes are particularly good cases for shedding light on the chemistry of the dppbt ligand, including its noninnocent nature, ligand-centered mechanism, and origin of differential reactivity. Density functional theory (DFT) combined with the high-level ab initio calculations performed herein demonstrates that, upon alkene/alkyne addition, the orbital symmetry properly regulates the reaction to form ligand-centered cis-interligand dithioethers as the most favorable pathway. The neutral and cationic Re and Ru dithioethers are revealed via DFT calculations to be in a low-spin ground state; on the contrary, high-level ab initio methods confirm that the dicationic Re-dithioethers exhibit obvious multireference character with antiferromagnetic coupling between Re-dyz and S1-py. The metal-stabilized thiyl radicals play a pivotal role in delivering the reactivity of [RuL3]+ and [ReL3]+/2+ toward alkene/alkyne rather than [ReL3], where [RuL3]+ and [ReL3]+/2+ present significant radical characters on ligand S2, yet neutral [ReL3] has little such feature, from which differential reactivity arises. Faster styrene addition to Ru tris(thiolate) in contrast to Re tris(thiolate) has been properly interpreted using DFT calculations with major products assigned. The deeper understanding gained in this work would illuminate further experimental exploration in adding alkene/alkyne to other metal-stabilized thiyl radicals.

Molecular Nickel Thiolate Complexes for Electrochemical Reduction of CO2 to C1–3 Hydrocarbons

AbstractWe report the unprecedented electrocatalytic activity of a series of molecular nickel thiolate complexes (1–5) in reducing CO2 to C1–3 hydrocarbons on carbon paper in pH‐neutral aqueous solutions. Ni(mpo)2 (3, mpo=2‐mercaptopyridyl‐N‐oxide), Ni(pyS)3− (4, pyS=2‐mercaptopyridine), and Ni(mp)2− (5, mp=2‐mercaptophenolate) were found to generate C3 products from CO2 for the first time in molecular complex. Compound 5 exhibits Faradaic efficiencies (FEs) of 10.6 %, 7.2 %, 8.2 % for C1, C2, C3 hydrocarbons respectively at −1.0 V versus the reversible hydrogen electrode. Addition of CO to the system significantly promotes the FEC1–C3 to 41.1 %, suggesting that a key Ni−CO intermediate is associated with catalysis. A variety of spectroscopies have been performed to show that the structures of nickel complexes remain intact during CO2 reduction.

Molecular Nickel Thiolate Complexes for Electrochemical Reduction of CO2 to C1-3 Hydrocarbons.

We report the unprecedented electrocatalytic activity of a series of molecular nickel thiolate complexes (1-5) in reducing CO2 to C1 - 3 hydrocarbons on carbon paper in pH-neutral aqueous solutions. Ni(mpo)2 (3, mpo = 2-mercaptopyridyl-N-oxide), Ni(pyS)3- (4, pyS = 2-mercaptopyridine), and Ni(mp)2- (5, mp = 2-mercaptophenolate) were found to generate C3 products from CO2 for the first time in molecular complex. Compound 5 exhibits Faradaic efficiencies (FEs) of 10.6%, 7.2%, 8.2% for C1, C2, C3 hydrocarbons respectively at -1.0 V versus the reversible hydrogen electrode. Addition of CO to the system significantly promotes the FEC1 - C3 to 41.1%, suggesting that a key Ni-CO intermediate is associated with catalysis. A variety of spectroscopies have been performed to show that the structures of nickel complexes remain intact during CO2 reduction.

Luminescent and sustainable d10 coinage metal thiolate coordination polymers for high-temperature optical sensing

The d10 coinage metal coordination polymers (CPs) are known to display photophysical properties which can be tuned depending on the functionality of the ligand. Three new CPs made of d10 coinage metals and methyl thiosalicylate, [M(o-SPhCO2Me)]n (M= Cu, Ag, Au), are reported. They are all constructed from one-dimensional metal-sulfur networks, in which Cu and Ag are three-coordinated to sulfur atoms, whereas Au is only two-coordinated. It results that both Cu(I) and Ag(I) CPs show orange photoemission at room temperature, and the Au(I) one exhibits near-infrared emission at low temperatures. The intense orange-emissive Ag(I) CP and the blue-emissive coumarin 120 have been mixed in an organic matrix, the polyvinylidene fluoride (PVDF), to form a dual luminescent flexible composite film. This film, evaluated for thermometry, shows great sensitivity for temperatures up to 100°C, a temperature never reached with non-lanthanide-based CPs.

A Series of Lithium Complexes of Bulky Rind-based Arylthiolate Ligands: Synthesis, Characterization, and Crystal Structures

The bulky Rind-based thiols, (Rind)SH (1) [Rind = 1,1,7,7-tetra-R1-3,3,5,5-tetra-R2-s-hydrindacen-4-yl: EMind (a: R1 = Et, R2 = Me), Eind (b: R1 = R2 = Et), and MPhind (c: R1 = Me, R2 = Ph)], reacted with nBuLi in THF to afford a series of lithium arylthiolates, [(Rind)SLi]n(THF)m (2), whose structures were confirmed by an X-ray diffraction analysis. In the solid state, while the less bulky EMind-based lithium thiolate exhibited a linear dimer, [(EMind)SLi]2(THF)4 (2a), or trimer, [(EMind)SLi]3(THF)5 (2a′), the monomeric structures of (Eind)SLi(THF)3 (2b) and (MPhind)SLi(THF)2 (2c) were found for the bulky Eind- and the bulkier MPhind-based systems. The salt metathesis reaction between 2a and FeCl2(THF)1.5 in THF produced the anionic three-coordinate planar Fe(II) thiolate complex, [Li(THF)3][{(EMind)S}3Fe] (3a).

The Notable Catalytic Activity of Transition Metal Thiolate Complexes against Hydrosilylation and Hydroboration of Carbon-Heteroatom Bonds.

Chemists tend to use transition metal hydride complexes rather than thiolate complexes to catalyse chemical transformations because the hydride complexes possess diverse catalytic reactivity although most of them are air/moisture sensitive and difficult to prepare. By comparing the catalytic performances of pincer ligated group 10 metal thiolate and hydride complexes in catalysing the hydroboration and hydrosilylation of C=O and C=N bonds, we demonstrate in this review that transition metal thiolate complexes are much better catalysts than the corresponding hydride complexes in catalysing this type of reactions. Many hydroboration and hydrosilylation reactions catalysed by pincer ligated group 10 metal hydride complexes can also be catalysed by the corresponding thiolate complexes and the thiolate systems are far more active. Therefore, the applications of transition metal thiolate complexes in the catalytic hydroboration and hydrosilylation of unsaturated carbon-heteroatom bonds deserve special attention in future work.

Coinage metal amido and thiolate SNS complexes: consequences of catalyst speciation in Cu(I)-catalysed carbonyl hydroboration.

Three new IPr-Ag- and -Au-SNS amido and thiolate complexes were synthesized and compared to their previously reported Cu analogues as carbonyl hydroboration catalysts (IPr = bis(2,6-diisopropylphenyl)imidazol-2-ylidene). Although these complexes showed no catalytic activity, treatment of the IPr-Ag-SNS amido complex with pinacolborane released the N-borylated ligand, SMeNBpinSMe, (L1-Bpin). This finding led us to reinvestigate the IPr-Cu-SNS amido precatalyst, revealing that immediate loss of L1-Bpin converts our catalyst system to [CuH(IPr)]2.

Structures of nickel chloride and thiolate complexes supported by PCN and POCOP pincer ligands and catalytic reactivity of the chloride complexes.

Nickel chloride and thiolate complexes supported by benzene-pyridine-based nonsymmetrical PCN pincer ligands, [2-(tBu2PO)-6-(2-pyrindinyl-4-R)-C6H3]NiX (R = H, CH3, CF3; X = Cl, SH, SPh), were synthesized and fully characterized. The structures of these complexes and the catalytic reactivity of the chloride complexes were investigated along with the related POCOP counterparts [2,6-(tBu2PO)2C6H3]NiX (X = Cl, SH). It was found that the composition and substitution of the pincer backbone evidently influence the structures and catalytic reactivity. The Ni-P and Ni-Cipso bond lengths in the PCN complexes are significantly shorter than those in the POCOP complex. The Ni-Cl and Ni-S bond lengths in the PCN complexes are longer than those in the POCOP complexes. An electron rich pyrindinyl ring in the PCN complexes makes the Ni-Cl bond longer. The Ni-N bond length is more sensitive to the auxiliary ligand compared with the Ni-P bond length in the PCN complexes. The PCN chloride complexes were found to be active catalysts for selective hydration of nitriles to primary amides in the presence of NaOH at 80 °C and the catalytic activity increases with the increase of electron richness of the pyridinyl ring. However, the corresponding POCOP counterpart is inactive under the same conditions.

Tetracopper(I) thiolate- and amido-(SNS) complexes and copper-catalyzed azide-alkyne cycloaddition in water.

Two tetranuclear Cu(I) complexes bearing thiolate- and amido-SNS ligands were characterized by X-ray diffraction and mass spectrometry. Although the amido ligand undergoes irreversible N-protonation by the copper-bound alkyne, the thiolate complex demonstrates good activity in the copper-catalyzed azide-alkyne cycloaddition reaction with a variety of substrates. The base-free reactions are performed in water and afford excellent yields over 2 h at 70 °C. DFT calculations suggest a proton-shuttle role for the thiolate donor in formation of the initial dicopper σ,π-alkynyl intermediate.

A binuclear guanidinate yttrium carbyne complex: unique reactivity toward unsaturated C-N, C-O and C-S bonds.

A guanidinato-stabilized binuclear yttrium carbyne complex [(PhCH2)2NC(NC6H3iPr2-2,6)2]2Y2(μ2-Me)(AlMe3)2(μ4-CH) (1) was synthesized via C-H bond activation and its versatile reactivities were investigated. Complex 1 underwent σ-bond metathesis with PhSSPh and nucleophilic addition with PhCN to form the corresponding yttrium thiolate complex 3 and aza-allyl complex 4 respectively. Additionally, the rare yttrium carbide complex 5 was also prepared by treatment of complex 1 with S8. Interestingly, in the reaction with PhNCS, the C[double bond, length as m-dash]S double bond was cleaved, followed by C-H bond activation to give the yttrium sulfide complex 7 with a ketenimine dianion ligand. Unexpectedly, the reaction of complex 1 with CO (1 atm) resulted in deoxygenative coupling of CO, to afford mono- or dioxo-yttrium complexes at different temperatures. The mechanism of the possible formation processes of complexes 3 and 9 was elucidated by DFT calculations.

On the Mechanism of Anti-galvanic Metal Displacement Reaction between [Au25(SR)18]- and Metal-Thiolate Complex.

Metal displacement reaction is widely used for preparing alloy nanomaterials. In this study, the mechanism of anti-galvanic metal displacement reaction between the atomic precision [Au25(SC2H4Ph)18]- cluster and the metal-thiolate complexes SR-M-SR (M = Ag, Cd, and Hg) is studied based on dispersion correction density functional theory (DFT-D) calculations. The present study reveals that the metal displacement reaction of the Au25 cluster is carried out through two-stage metal diffusion including the rapid diffusion of the metal heteroatom from metal thiolate to the ligand layer of Au25 cluster and then gradual diffusion of the metal heteroatom into the icosahedral 13-atom core. The atomic charge analysis confirms that the SR group plays a crucial role. Due to the partial reducibility of SR group, it can nucleophilic attack Au atom to result in the fracture of the Au-S bond in the ligand layer and the formation of atomic vacancy on the surface of the metal core, which facilitates the metal heteroatom diffusion from the metal-SR complex to the ligand layer of gold cluster and then to the surface of gold core.

Experimental and DFT study of the kinetics of the interaction of Pt(II) and Pd(II) with disulfides in hydrochloric acid solutions

In this paper, the kinetics and mechanistic studies of the kinetics of the interaction of [PtCl4]2− and [PdCl4]2− with cystine, cystamine, homocystine, and dithiodipropionic acid have been reported. The direction of the reaction primarily depends on the nature of the metal. The rate-limiting step for the interaction [PtCl4]2− with cystine and dithiodipropionic acid is the formation of S,S-binuclear disulfide platinum complex [Pt2Cl6(R-SS-R)]; for cystamine is the formation of S-disulfide platinum complex [PtCl3(R-SS-R)]; and for homocystine is the formation of the platinum(IV) thiol complex [PtCl4(S-R)2]. The rate-limiting step for the interaction [PdCl4]2− with cystine is the formation of S,S-binuclear disulfide platinum complex [Pd2Cl6(R-SS-R)]; for homocystine is the formation of S-disulfide platinum complex [PdCl3(R-SS-R)]; for cystamine, the rate-limiting step are represented by the contributions of the formation of both mono and binuclear disulfide complexes; and for dithiodipropionic acid is the hydrolysis of the binuclear S,S′-disulfide palladium complex.

Calculation of Resonance Raman Spectra and Excited State Properties for Blue Copper Protein Model Complexes

Laccase enzymes have been investigated for their potential as eco-friendly biofuel cell cathode catalysts. In these applications, electrons transfer from the electrode directly to the so-called Type 1 (T1) redox site within the enzyme. Over the years, resonance Raman (RR) spectroscopy has been utilized to probe the nature of ligand interactions with the Cu2+ center at the T1 site of the resting, oxidized form of laccases and related blue copper proteins. Spectral interpretation has been guided by parallel studies of small molecule T1 site mimics. Reported herein are results of time-dependent density functional theory (TDDFT) calculations performed on a series of experimentally well-studied T1 site mimics based on Cu2+ thiolate complexes stabilized by either a tridentate tris(pyrazolyl)hydroborate ligand or a bidentate β-diketiminate ligand. Vertical excitation energies were computed for the first 10 doublet states of each complex. The electronic absorption and RR spectra derived show excellent agreement with the experiment. RR spectra were dominated by a strong Cu–S stretching transition near 400 cm–1, which is sensitive to molecular conformation within the thiolate ligand. The results provide a foundation to build from in advancing models of laccase catalytic active sites in support of sustainable technologies.

Depletion Driven Assembly of Ultrasmall Metal Nanoclusters: From Kinetically Arrested Assemblies to Thermodynamically Stable, Spherical Superclusters.

Nanoscale assembly of ultrasmall metal nanoclusters (MNCs) by means of molecular forces has proven to be a powerful strategy to engineer their molecule-like properties in multiscale dimensions. By leveraging depletion attraction as the guiding force, herein, we demonstrate the formation of kinetically trapped NCs assemblies with enhanced photoluminescence (PL) and excited state lifetimes and extend the principle to cluster impregnated cationic nanogels, nonluminescent Au(I)-thiolate complexes, and weakly luminescent CuNCs. We further demonstrate a thermal energy driven kinetic barrier breaking process to isolate these assemblies. These isolated assemblies are thermodynamically stable, built from a strong network among several discrete, ultrasmall AuNCs and exhibit several unusual properties such as high stability in various pH, strong PL, microsecond lifetimes, large Stocks shifts, and higher accumulation in the lysosome of cancer cells. We anticipate our strategy may find wider use in creating a large variety of MNC-based assemblies with many unforeseen arrangements, properties, and applications.

Photoluminescence in halogeno copper(Ⅰ) methyl thiolate polymers via in situ DMSO decomposition reaction

Five halogeno-copper thiolate coordination polymers, Cu12Cl6(SCH3)6(DMSO) 1, Cu3X(SCH3)2 (2, 4), and Cu2X(SCH3) (X = Br, I) (3, 5) were solvothermally prepared by employing DMSO, which is used as a thiolate source via in situ decomposition. The X-ray crystallographic data revealed one type of 3D network structure composed of Atlas spheres. Additionally, two types of 2D layered bromo/iodo isostructural complexes were found, and the differences between these two types are attributed to the different connection modes of their Cu3X2(SCH3)2 chains. Sharing the halogen atoms in Cu3X2(SCH3)2 chain or bridging the chains via additional copper atoms could lead to the formation of different layers with a Cu:X:SCH3 ratio of 3:1:2 or 2:1:1, respectively. The absorption and emission spectral data described the influence of the ratio and species of halogen elements in copper thiolate complexes. From the spectroscopic studies, long-lived phosphorescence was detected, the characteristic lifetime of which depends on the crystal internal structures as well as the constituent halogen atoms.

Structural investigations and reactivity of cobalt(II)–disulfide compounds

Controlling the bio-inspired redox conversion of Co(II)–disulfide compounds to their related Co(III)–thiolate complexes is a perplexing task as the factors triggering this reaction are not fully understood. Three disulfide ligands 2,2′–disulfanediylbis(N,N-bis((3,5–dimethyl-1H–pyrazol–1–yl)methyl)ethan-1-amine) (LmpzSSLmpz), 3,3′-disulfanedylbis(N,N-bis(pyridin-2-ylmethyl)propan-1-amine) (LpSSLp), and 2,2′-disulfanediylbis(N,N-bis(6-methylpyridin-2–ylmethyl)ethan-1–amine) (L3SSL3) with different chain lengths and pyrazole or pyridine groups were reacted with cobalt(II) salts and the resulting complexes were studied for their potential to form Co(III)–thiolate complexes. Crystal structures of [Co2(LmpzSSLmpz)(Br)4] [1Br], [Co2(LmpzSSLmpz)(NCS)4] [1NCS], [Co2(LpSSLp)(NCS)4] [2NCS], and [Co2(L3SSL3)(Cl)4] [3Cl] show that generally the disulfide sulfur donors do not coordinate to the cobalt(II) centers, resulting in dinuclear structures containing two 5-coordinate cobalt centers. However, a unique asymmetric structure is found in [1Br] in which one of the sulfur atoms coordinates to one of the cobalt ions. Thiocyanate–induced Co(III)–thiolate formation in the presence of either ligand LmpzSSLmpz or LpSSLp is evidently unsuccessful, as Co(II)–disulfide complexes were obtained. The reaction of the Co(II)–disulfide complexes with 8-quinolinol suggest that redox conversion to Co(III)–thiolate complexes may take place, but the reactions are not clean.

The catalytic activity difference of bis(phosphinite) pincer ligated Pt(II) thiolate and hydride complexes against hydrosilylation of aldimines

• POCOP pincer Pt thiolate and hydride complexes are good catalysts for hydrosilylation of aldimines • The thiolate complexes are more active than the hydride complexes • The reactions feature with good functional group compatibility and wide substrate scope • The expected amine products can be isolated in good to excellent yields In order to get information about the catalytic activities of bis(phosphinite) (POCOP) pincer ligated group 10 metal thiolate and hydride complexes against the hydrosilylation of unsaturated carbon-heteroatom bonds, platinum(II) complexes [2,6-( t Bu 2 PO) 2 C 6 H 3 ]PtX (X = SH, 1a; SPh, 1b; H, 1c) and [2,6-( i Pr 2 PO) 2 C 6 H 3 ]PtH (2) were applied to the catalytic hydrosilylation of aldimines. It was found that both auxiliary ligand and donor substituent play very important roles in affecting the catalytic activity of the platinum center. The hydride complex 1c is almost inactive in catalyzing the reactions; however, the hydride complex 2, which processes less bulky donor substituents ( i Pr vs t Bu), is an active catalyst. Meanwhile, the thiolate complexes 1a and 1b, which have the same donor substituents as 1c, are active catalysts and 1a is among most effective catalysts for this type of reaction. The catalytic reactions are featured with a wide substrate scope with relatively high turnover frequencies. Both aromatic and aliphatic aldimines were successfully hydrosilylated and the expected amines were isolated in good to excellent yields after basic hydrolysis of the hydrosilylation products. Functional groups such as OMe, halogens and internal C=C double bond were unaffected during the reactions. Although the hydride complex 2 is an active catalyst, it is less effective than the thiolate complex 1a despite the fact that the metal center in 2 is less sterically hindered by the donor substituents. As a result, the thiolate complexes are more active than the hydride complexes in catalyzing the reactions. The possible reasons for the different catalytic activities of these complexes are discussed.