Square-Planar Nickel Bis(phosphinopyridyl) Complexes for Long-Lived Photocatalytic Hydrogen Evolution.

Phosphinopyridyl ligands are used to synthesize a class of Ni(II) bis(chelate) complexes, which have been comprehensively characterized in both solid and solution phases. The structures display a square-planar configuration within the primary coordination sphere, with axially positioned labile binding sites. Their electrochemical data reveal two redox couples during the reduction process, suggesting the possibility of accessing two-electron reduction states.

Reversible Conversion of Disulfide/Dithiolate Occurring at a Vanadium(IV) Center: A Biomimetic System for Redox Exchange in Vanabin.

Ascidians use a class of cysteine-rich proteins generally referred to as vanabins to reduce vanadium ions, one of the many biological processes that involve the redox conversion between disulfide and dithiolate mediated by transition-metal ions. To further understand the nature of disulfide/dithiolate exchange facilitated by a vanadium center, we report herein a six-coordinate non-oxido V complex containing an unbound disulfide moiety, [V(PS3″)(PS1″)] () (PS3″ = [P(CH-3-MeSi-2-S)], where PS1″ is a disulfide form of PS3″). Complex is obtained from a reaction of previously reported [V(PS3″)(PS2″S)] () (PS2″S = [P(CH-3-MeSi-2-SH)(CH-3-MeSi-2-S)] with TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidin-1-yl)oxyl) via hydrogen atom transfer.

Structural and Spectroscopic Evidence for a Side-on Fe(III)-Superoxo Complex Featuring Discrete O-O Bond Distances.

The O-O bond length is often used as a structural indicator to determine the valence states of bound O ligands in biological metal-dioxygen intermediates and related biomimetic complexes. Here, we report very distinct O-O bond lengths found for three crystallographic forms (1.229(4), 1.

The dual roles of a V(III) centre for substrate binding and oxygen atom abstraction; nitrite reduction mediated by a V(III) complex.

A V(iii) complex bearing a tris(thiolato)phoshine derivative mediates the reduction of nitrite without the assistance of external protons or oxophilic substrates. The metal site plays dual roles for nitrite binding and deoxygenation. The reaction is monitored by spectroscopy combined with isotopic labeling experiments.

Ligand-Based Reactivity of Oxygenation and Alkylation in Cobalt Complexes Binding with (Thiolato)phosphine Derivatives.

In our efforts to understand the nature of metal thiolates, we have explored the chemistry of cobalt ion supported by (thiolato)phosphine ligand derivatives. Herein, we synthesized and characterized a square-planar Co complex binding with a bidentate (thiolato)phosphine ligand, Co(PS1″) () ([PS1″] = [P(Ph)(CH-3-SiMe-2-S)]). The complex activates O to form a ligand-based oxygenation product, Co(OPS1″) () ([OPS1″] = [PO(Ph)(CH-3-SiMe-2-S)]).

Antimetastatic effects of Terminalia catappa leaf extracts on cervical cancer through the inhibition of matrix metalloprotein-9 and MAPK pathway.

The effects of Terminalia catappa leaf extracts (TCE) have been widely investigated, including its antioxidative, anti-inflammatory, and antidiabetic activity, as well as its antimetastatic effects on several types of human cancer. However, no study has examined the antimetastatic potential of TCE in cervical cancer cells. This study aimed to elucidate the potential antimetastatic properties of ethanol extracts of Terminalia catappa in 12-O-tetradecanoylphorbol-13-acetate treated human cervical cancer cells and investigate the signaling pathway of this process.

Activation of O-H and C-O Bonds in Water and Methanol by a Vanadium-Bound Thiyl Radical.

The reaction of [V(PS3")] (1) (PS3"=[P(C H -3-Me Si-2-S) ] ) with H O led to the formation of [V (PS3")(PS2"S )] (2) (PS2"S =[P(C H -3-Me Si-2-S) (C H -3-Me Si-2-SH)] ), indicating a hydrogen atom transfer from H O to a bound thiolate in 1. Furthermore, the reaction of 1 with CH OH gave the generation of complexes 2 and 3, [V (PS3")(PS2"S )] (PS2"S =[P(C H -3-Me Si-2-S) (C H -3-Me Si-2-SCH )] ), implying that C-O and O-H bonds are cleaved by 1. Quantum mechanical calculations were performed to provide the mechanistic understanding for the reactivity of 1 with water.

Redox Interconversion of Non-Oxido Vanadium Complexes Accompanied by Acid-Base Chemistry of Thiol and Thiolate.

The redox nature of the non-oxido vanadium sulfur center is associated with several biological systems such as vanadium nitrogenase, the reduction of vanadium ion in ascidians, and the function of amavadin, which is a vanadium(IV) natural product contained in Amanita mushrooms. But the related chemistry is less explored and understood compared to oxido vanadium species due to the oxophilic character of high valent vanadium ions. Herein, we present a class of non-oxido vanadium thiolate complexes, [V(PS2″S)] (1) (PS2″S = [P(CH-3-MeSi-2-S)(CH-3-MeSi-2-SH)]), [V(PS3″)(PS2″S)] (2) (PS3″ = [P(CH-3-MeSi-2-S)]), [V(PS3″)] (3), [V(PS3″)(PS2″S)] (4), and [V(PS3*)] (5a) (PS3* = [P(CH-3-Ph-2-S)]), and study their interconversion through the redox and acid-base reactions.

Spin-Polarization-Induced Preedge Transitions in the Sulfur K-Edge XAS Spectra of Open-Shell Transition-Metal Sulfates: Spectroscopic Validation of σ-Bond Electron Transfer.

Sulfur K-edge X-ray absorption spectroscopy (XAS) spectra of the monodentate sulfate complexes [M(itao)(SO)(HO)] (M = Co, Ni, Cu) and [Cu(Metren)(SO)] exhibit well-defined preedge transitions at 2479.4, 2479.9, 2478.

A non-oxo methanolate-bridged divanadium(IV) complex with tris(2-sulfanidylphenyl)phosphane ligands: synthesis, structural characterization and magnetic investigation.

Vanadium chemistry is of interest due its biological relevance and medical applications. In particular, the interactions of high-valent vanadium ions with sulfur-containing biologically important molecules, such as cysteine and glutathione, might be related to the redox conversion of vanadium in ascidians, the function of amavadin (a vanadium-containing anion) and the antidiabetic behaviour of vanadium compounds. A mechanistic understanding of these aspects is important.

Reactivity of a Fe(III)-Bound Methoxide Supported with a Tris(thiolato)phosphine Ligand: Activation of C-Cl Bond in CH2Cl2 by Nucleophilic Attack of a Fe(III)-OCH3 Moiety.

Two mononuclear nonheme Fe(III) complexes, [PPh4][Fe(III)(PS3″)(OCH3)] (1) and [PPh4][Fe(III)(PS3″)(Cl)] (2), supported by a tris(benzenethiolato)phosphine derivative PS3″ (PS3″ = P(C6H3-3-Me3Si-2-S)3(3-)) have been synthesized and characterized. The structures resolved from X-ray crystallography show that Fe(III) centers in both complexes adopt distorted trigonal-bipyramidal geometry with a methoxide or a chloride binding in the axial position. The magnetic data for both are consistent with intermediate-spin Fe(III) centers with a C3 symmetry (S = 3/2 ground state).

Non-oxido divanadium(IV) and divanadium(V) thiolate complexes with a new type of chalcogenide bridging motif.

In our effort to study vanadium chalcogenide chemistry, we have synthesized and characterized a class of non-oxido divanadium(IV) and divanadium(V) complexes with chalcogenide and dichalcogenide as bridges. All structures consist of a similar divanadium motif, in which two metal centers are bridged by one μ-chalcogenide and one μ-η(2):η(2)-dichalcogenide, forming a V2(μ-E)(μ-η(2):η(2)-E2) (E = S or Se) core structure. These compounds are [V(IV)2(PS3)2(μ-Se2)(μ-Se)][PPh4]2 (1), [V(V)2(PS3'')2(μ-Se2)(μ-Se)] (2), [V(V)2(PS3'')2(μ-S2)(μ-S)] (3a) and [V(V)2(PS3)2(μ-S2)(μ-S)] (3b) ([PS3](3-) = P(C6H4-2-S)3 and [PS3''](3-) = P(C6H3-3-SiMe3-2-S)3).

Oligonucleotides--assembled Au nanorod-assisted cancer photothermal ablation and combination chemotherapy with targeted dual-drug delivery of Doxorubicin and Cisplatin prodrug.

External stimuli responsive dual drugs carrier was synthesized with Au nanorods (NRs) as the platform. On Au NRs, single stranded DNAs were assembled using 5' thiol end. Following this, complementary DNA (cDNA) strands were hybridized.

Catalytic reduction of hydrazine to ammonia by a mononuclear iron(II) complex on a tris(thiolato)phosphine platform.

To provide the mechanistic information of nitrogenase at a molecular level, much effort has been made to develop synthetic metal complexes that have enzyme-like reactivity. Herein we obtain an iron(II) complex binding with a tris(thiolato)phosphine ligand, [P(Ph)4][Fe(PS3″)(CH3CN)] [1; PS3″ = P(C6H3-3-Me3Si-2-S)3(3-)] that catalyzes the reduction of hydrazine, an intermediate and a substrate of nitrogenase. The substrate- and product-bound adducts, [N(Bu)4][Fe(PS3″)(N2H4)] (2) and [N(Et)4][Fe(PS3″)(NH3)] (3), respectively, are also synthesized.

Activation of dichloromethane by a V(III) thiolate complex: an example of S-based nucleophilic reactivity in an early transition metal thiolate.

A V(III) thiolate complex activated C-Cl bond in dichloromethane via S-based nucleophilic attack. The reaction products, a V(III)-Cl species (major one) and a V(IV) binding to a CH(2) containing ligand (minor one) were obtained. The work demonstrates sulfur donors in the early-transition metal thiolates having strong nucleophilic characteristics.

An eight-coordinate vanadium thiolate complex with charge delocalization between V(V)-thiolate and V(IV)-thiyl radical forms.

A six-coordinate oxovanadium(V) thiolate complex and an eight-coordinate non-oxovanadium thiolate complex, [PPh(4)][VO(PS3'')(OCH(3))] (1) and [NEt(4)][V(PS3'')(2)] (2) (PS3'' = P(C(6)H(3)-3-Me(3)Si-2-S)(3)(3-)), respectively, have been isolated and structurally characterized. The former belongs to a limited collection of oxovanadium(V) thiolate complexes. The latter has an unusual coordination number of eight.

A comparative study on arsenic and humic substances in alluvial aquifers of Bengal delta plain (NW Bangladesh), Chianan plain (SW Taiwan) and Lanyang plain (NE Taiwan): implication of arsenic mobilization mechanisms.

Humic substances in groundwater and aquifer sediments from the arsenicosis and Blackfoot disease (BFD) affected areas in Bangladesh (Bengal delta plain) and Taiwan (Lanyang plain and Chianan plain) were characterized using fluorescence spectrophotometry and Fourier transform infrared (FT-IR) spectroscopy. The results demonstrate that the mean concentration of As and relative intensity of fluorescent humic substances are higher in the Chianan plain groundwater than those in the Lanyang plain and Bengal delta plain groundwater. The mean As concentrations in Bengal delta plain, Chianan plain, and Lanyang plain are 50.

Tetra-butyl-ammonium bis-[4,4'-dimethyl-2,2'-(3,7-dimethyl-1H-4,2,1-benzothiaza-siline-1,1-di-yl)dibenzene-thiol-ato]vanadium(III) acetonitrile tetra-solvate.

In the title compound, [N(C(4)H(9))(4)][V(C(23)H(21)NS(3)Si)(2)]·4CH(3)CN, the V(III) atom (site symmetry ) is coordinated by two N,S,S'-tridentate 4,4'-dimethyl-2,2'-(3,7-dimethyl-1H-4,2,1-benzothiaza-siline-1,1-di-yl)dibenzene-thiol-ate ligands in a distorted trans-VN(2)S(4) octa-hedral geometry. The complete cation is generated by crystallographic twofold symmetry, with the V atom lying on the rotation axis. The unusual ligand arose from nucleophilic attack on the coordinated nitrile by the thiol-ate precursor and reduction of nitrile to the imidate.

Family of V(III)-tristhiolato complexes relevant to functional models of vanadium nitrogenase: synthesis and electronic structure investigations by means of high-frequency and -field electron paramagnetic resonance coupled to quantum chemical computations.

A series of V(III) complexes of varying coordination number (5, 6, and 7) all containing the PS3 ligand (PS3 = trianion of tris(2-thiophenyl)phosphine and its derivatives with other phenyl substituents) has been prepared and structurally characterized. The complexes have general formula [V(PS3)L(n)](0,-), where n = 1 (from L = Cl(-), 1-Me-Im, N(3)(-)), 2 (from L = 2,2'-bpy; counting each N of the bidentate ligand), and 3 (from L = 1-Me-Im, N(2)H(4)). The complexes have also been investigated by direct current (DC) magnetic susceptibility and high-frequency and -field electron paramagnetic resonance (HFEPR).

Aminocarboxylate complexes of vanadium(III): Electronic structure investigation by high-frequency and -field electron paramagnetic resonance spectroscopy.

Aminocarboxylate complexes of vanadium(III) are of interest as models for biologically and medicinally relevant forms of this interesting and somewhat neglected ion. The V(III) ion is paramagnetic, but not readily suited to conventional EPR, due to its integer-spin ground state (S=1) and associated large zero-field splitting (zfs). High-frequency and -field EPR (HFEPR), however, has the ability to study such systems effectively.

The prophylactic protective effect of sesamol against ferric-nitrilotriacetate-induced acute renal injury in mice.

The aim of this study was to examine the prophylactic protective effects of 3,4-methylenedioxyphenol (sesamol) on ferric-nitrilotriacetate (Fe-NTA)-induced acute renal damage in mice. We induced acute renal injury in mice by treating them with 4 mg/kg of Fe-NTA for 3h. We used blood biochemistry, creatinine clearance, and histological examinations to assess renal function.

Dinuclear oxovanadium(IV) thiolate complexes with ferromagnetically coupled interaction between vanadium centers.

Two dinuclear oxovanadium(IV) thiolate complexes, [N(C5H11)4]2[VOL1]2 (1) and [N(C4H9)4][(VOL2)2(mu-OCH3)] (2) (where L1 = [(CH3)SiO(C6H4-2-S)2]3- and L2 = [(C6H5)PO(C6H4-2-S)2]2-), have been synthesized and characterized. The geometry of the anion in 1 can be classified to an edge-sharing bi-square-pyramid with a syn-orthogonal configuration. The one in 2 can be view as a face-sharing bioctahedron with two oxo groups in syn positions.

Electronic structure and FeNO conformation of nonheme iron-thiolate-NO complexes: an experimental and DFT study.

Reactions of NO and CO with Fe(II) complexes of the tripodal trithiolate ligands NS3 and PS3* yield trigonal-bipyramidal (TBP) complexes with varying redox states and reactivity patterns with respect to dissociation of the diatomic ligand. The previously reported four-coordinate [Fe(II)(NS3)](-) complex reacts irreversibly with NO gas to yield the S = 3/2 {FeNO}(7) [Fe(NS3)(NO)](-) anion, isolated as the Me(4)N(+) salt. In contrast, the reaction of NO with the species generated by the reaction of FeCl(2) with Li(3)PS3* gives a high yield of the neutral, TBP, S = 1 complex, [Fe(PS3*)(NO)], the first example of a paramagnetic {FeNO}(6) complex.

Catalytic reduction of hydrazine to ammonia by a vanadium thiolate complex.

Vanadium(III) thiolate complexes, [V(PS3'')(Cl)]- [1a; PS3'' = P(C6H3-3-Me3Si-2-S)3(3-)] and [V(PS3')(Cl)]- [1b; PS3' = P(C6H3-5-Me-2-S)3(3-)], were synthesized and characterized. Complex 1a serves as a precursor for the catalytic reduction of hydrazine to ammonia. The spectroscopic and electrochemical studies indicate that hydrazine is bound and activated in a V(II) state.

The first example of a seven-coordinate vanadium(III) thiolate complex containing the hydrazine molecule, an intermediate of nitrogen fixation.

The first example of a seven-coordinate vanadium(III) thiolate complex, [V(PS3' ')(N(2)H(4))(3)] (1), where PS3' ' = [P(C(6)H(3)-3-Me(3)Si-2-S)(3)](3)(-), has been synthesized and characterized. Compound 1 contains a tetradentate ligand (PS3' ') and three hydrazine molecules, forming a capped octahedral geometry. A five-coordinate vanadium(III) complex, [V(PS3)(1-Me-Im)] (2), where PS3 = [P(C(6)H(4)-2-S)(3)](3)(-) and 1-Me-Im = 1-methyl-imidazole, was also obtained.