Sulfur Donor Ligands Research Articles

The Bioinorganic Chemistry of Mammalian Metallothioneins.

The functions, purposes, and roles of metallothioneins have been the subject of speculations since the discovery of the protein over 60 years ago. This article guides through the history of investigations and resolves multiple contentions by providing new interpretations of the structure-stability-function relationship. It challenges the dogma that the biologically relevant structure of the mammalian proteins is only the one determined by X-ray diffraction and NMR spectroscopy. The terms metallothionein and thionein are ambiguous and insufficient to understand biological function. The proteins need to be seen in their biological context, which limits and defines the chemistry possible. They exist in multiple forms with different degrees of metalation and types of metal ions. The homoleptic thiolate coordination of mammalian metallothioneins is important for their molecular mechanism. It endows the proteins with redox activity and a specific pH dependence of their metal affinities. The proteins, therefore, also exist in different redox states of the sulfur donor ligands. Their coordination dynamics allows a vast conformational landscape for interactions with other proteins and ligands. Many fundamental signal transduction pathways regulate the expression of the dozen of human metallothionein genes. Recent advances in understanding the control of cellular zinc and copper homeostasis are the foundation for suggesting that mammalian metallothioneins provide a highly dynamic, regulated, and uniquely biological metal buffer to control the availability, fluctuations, and signaling transients of the most competitive Zn(II) and Cu(I) ions in cellular space and time.

Synthesis, spectral and sol-gel behavior of mixed ligand complexes of titanium(IV) with oxygen, nitrogen and sulfur donor ligands

A new route to synthesize nano-sized Ti(IV) mixed ligand complexes have been investigated by the reaction of titanium(IV) chloride with ammonium salts of dithiophosphate and 3(2'-hydroxyphenyl)-5-(4-substituted phenyl) pyrazolines. The resultant complex is then treated with H2S gas to get sulfur bridged dimer of Ti(IV) complex, a precursor of TiS2. The morphology of the complexes was studied by employing XRD which shows that all the complexes are amorphous solid. Molecular weight measurements, elemental analysis in conjugation with spectroscopic (IR, 1H NMR, 13C NMR and 31P NMR) studies revealed the dimeric nature of the complexes in which pyrazoline and dithiophosphate are bidentate. Scanning electron microscopic image and XRD indicate that the particles are in the nano range (50 nm). Putting all the facts together, coordination number six is proposed for titanium with octahedral geometry.
 
 KEY WORDS: Titanium(IV), Dithiophosphate, Pyrazoline, Nano-sized, Sol-gel, Mixed ligand complexes
 
 Bull. Chem. Soc. Ethiop. 2021, 35(1), 61-76.
 DOI: https://dx.doi.org/10.4314/bcse.v35i1.5

Extraction of the trivalent transplutonium actinides americium through einsteinium by the sulfur donor Cyanex 301

When extracting metals with the sulfur donor ligand, Cyanex 301 (bis(2,4,4-trimethylpentyl)dithiophosphinic acid), a transition in the coordination mode of extracted complexes has been observed between Eu and Gd, but not within the actinide series.

Structure and Characterization of an Americium Bis(O,O'-diethyl)dithiophosphate Complex.

A facile synthesis of an americium complex with a sulfur-donor ligand has been developed, allowing characterization of americium bonding from multiple perspectives via several techniques. Reaction of 243Am with S2P(OEt)2- yields the tetrakis complex [Am(S2P(OEt)2)4]- that can be crystallized as the tetraphenylarsonium salt. Structures obtained from single crystal X-ray diffraction show bond length discrepancies from the neodymium analogue consistent with the soft-donor bond enhancement common to actinides. Solid state optical spectroscopy confirms interaction of the ligand with 5f orbitals. 31P nuclear magnetic reflects the minor paramagnetism of Am(III). Computational investigations through CASSCF calculations, ligand-field density functional theory, and quantum chemical topological analysis allow a quantification of covalency or orbital interaction effects via total energy density and nephelauxetic parameters, both of which indicate greater covalency in the americium species than in the neodymium analogue or the americium aquo complex.

Micro-level Estimation of Mercaptoacetic Acid Using its Inhibitory Effect to Mercury Catalyzed Ligand Exchange Reaction of Hexacyanoruthenate(II)

The sulfur-containing bioactive molecules (soft base) tends to bind strongly with Hg(II) (soft acid), thereby inhibiting the mercury (II) catalyzed exchange rate of cyanide ligand from [Ru(CN)6]4- by pyrazine. This inhibitory effect of Mercaptoacetic acid (MAA) encourages us to establish a new kinetic method for its micro-level estimation. Optimized reaction condition viz. 6.25×10-5 M [Ru(CN)64-], pH = 4.0, 7.5×10-4 M [Pyrazine], 0.05 M KCl, 8.5 ×10-5 M [Hg+2] and 45 (±0.1) oC temperature were utilized for the kinetic spectrophotometric investigation at 370nm (λmax of [Ru(CN)5 Pz]3- complex). The modified mechanistic scheme for inhibition caused by sulfur donor ligand, MAA has been proposed. The proposed analytical method provides the detection of MAA up to 2.0 × 10-6 M, indicates that the methodology can be effectively and economically employed to analyze the biological samples having MAA. This method can also be convincingly adopted for the quality check of MAA containing industrial products.

Synthesis, characterization, anticancer activity and biological activities of vanadium complexes of 2-mercapto-5-methyl-benzimidazole as sulphur donor ligand

Vanadium complexes have been synthesized by the reaction of mercapto methyl benzimidazole with carbon disulphide and then with different vanadium salts in different M L ratio The synthesized vanadium complexes have been characterized by elemental microanalysis CHN FT IR spectroscopy and NMR H C spectroscopy Elemental analysis data shows good agreement between found and calculated values FT IR spectroscopic data suggests the bidentate nature of the ligand The results of multinuclear NMR revealed that coordination occurs through NCS moiety Antibacterial activity data showed that ligand and complexes showed moderate antibacterial and anti biofilm activity The cytotoxicity studies showed that vanadium complex is less cytotoxic and complex has maximum cytotoxicity In vitrooxidative DNA damage protection assay showed that synthesized vanadium complexes exhibited plasmid DNA protection by scavenging the oxidation products Results of in vitro anticancer activity showed that oxoperoxo vanadium complex exhibited significant anticancer activity IC mu M against H MX cell line

Biological Applications of Thiocarbohydrazones and Their Metal Complexes: A Perspective Review.

Although organic compounds account for more than 99% of currently approved clinical drugs, the established clinical use of cisplatin in cancer or auranofin in rheumatoid arthritis have paved the way to several research initiatives to identify metal-based drugs for a wide range of human diseases. Nitrogen and sulfur donor ligands, characterized by different binding motifs, have been the subject in recent years of one of the main research areas in coordination chemistry. Among the nitrogen/sulfur compounds, very little is known about thiocarbohydrazones (TCH), the higher homologues of the well-known thiosemicarbazones (TSC), and their metal complexes. The extra hydrazine moiety provides the ligands of variable metal binding modes, structural diversity and promising biological implications. The interesting coordination chemistry of TCH has mainly been focused on symmetric derivatives, which are relatively simple to synthesize while few examples of asymmetric ligands have been reported. This informative review on TCHs and their metal complexes will be helpful for improving the design of metal-based pharmaceuticals for applications ranging from anticancer to antinfective therapy.

Bifunctional sulfur-ligated erbium complex: Crystal structure, magnetic and luminescent properties

Two isostructural mononuclear rare-earth complexes, [(dbm)2Er(dtc)(phen)] (1-Er) and [(dbm)2Tb(dtc)(phen)] (2-Tb) (dbm− = dibenzoylmethanoate anion, dtc− = diethyldithiocarbamate anion, phen = 1, 10-phenanthroline) were synthesized and structurally characterized by single-crystal X-ray diffraction analyses. Each complex consists of one sulfur-donor ligand, two oxygen-donor ligands and one auxiliary ligand, and Er3+/Tb3+ ion locates in a distorted square antiprism. Magnetic measurements show that 1-Er displays slow magnetic relaxation behavior under an applied field, and solid-state emission spectra reveal that 1-Er exhibits characteristic emissions of Er3+ ion in the visible and near-infrared regions, indicating the dual functionality of 1-Er. Neither slow relaxation of the magnetization nor characteristic emissions of Tb3+ ion were observed for 2-Tb.

The First Bis(μ‐acetato)(μ‐oxido)diruthenium(III) Complexes Containing Sulfur Donor Ligands

AbstractNovel diruthenium(III) complexes of general formula [RuIII2(μ‐O)‐(μ‐CH3CO2)2(bpy)2L2](PF6)2 (L: tetrahydrothiophene, (3); 4,5‐dihydro‐3(2H)‐thiophenone, (4); thiazole, (5); 4‐methylthiazole, (6); bpy: 2,2’‐bipyridine), which contain sulfur or nitrogen donor ligands at the trans‐to‐oxido sites, have been synthesized. The Ru–S bond distance in 4 is determined by X‐ray crystallography to be 2.447 Å, and the Ru–N(trans‐to‐oxido) length in 5 (2.157 Å) is similar to that of the complex having pyridine as the L ligand, 1. The spectroscopic properties and redox behavior of the complexes bearing sulfur donor ligands have been investigated and compared with those containing nitrogen donor ligands. The potentials of the redox couples of Ru2II,III/Ru2III,III and Ru2III,III/Ru2III,IV for 3 and 4 shift to positive regions compared with those of complexes with nitrogen donor ligands, 1, 5 and 6. The density functional theory (DFT) calculations reveal that the contribution of the trans ligand to the visible absorption is larger in 3 and 4 than in 1, 2 (L: CH3CN), 5 and 6.

Mixed arsenic(III) bis(dimethyldithiocarbamato) derivatives with some oxygen and sulfur donor ligands

Seven mixed arsenic(III) bis(dimethyldithiocarbamato) derivatives of type [(CH3)2NCS2]2AsL where, L = OOCC6H5, OOCCH3, OOCC6H4(OH), SC6H5, SCH2COOH, SOCCH3 and S(C6H4)COOH have been synthesized and characterized by various physicochemical [elemental analysis (C, H, N, S & As), molecular weight and melting point determinations], spectral [UV–Vis., FTIR, NMR (1H and 13C)], thermal [TGA and DTG], powder XRD studies. The presence of FT-IR band at 1064–1095 cm−1 due to thiocarbonyl moity and 13C NMR signal in the range 192.56–198.59 ppm due to -NCS2 carbon resonance have indicated anisobidentate mode of bonding of dithiocarbamate group, alongwith this FT far-IR bands observed due to the υ(As–O) and υ(As–S) vibrations in the region 530–532 cm−1 and 302–333 cm−1 respectively, confirm the bonding of arsenic(III) to oxygen and sulfur. Thus, on the basis of results obtained by above spectral techniques, it may be concluded tentatively that, arsenic(III) derivatives (compound 1–7) adopted a distorted octahedral geometry with lone pair of electrons occupying one of the corner of octahedra. Powder XRD studies revealed that these derivatives have nano ranged particle size (5.72 and 16.29 nm) with lower symmetry (monoclinic) crystal system along with unit cell volume (1731 and 1764 Å3). Thermal studies reveal that arsenic(III) bis(dimethyldithiocarbamato) thiosalicylate (compound 7) gives arsenic sulfide as a final decomposition product, which have various potential applications. Antimicrobial screening test showed enhanced activity than free ligands and standard drugs.

Synthesis and Characterization of Mixed Ligand Complexes of Zirconium(IV) with Sulphur, Nitrogen and Oxygen Donor Ligands

Synthesis and Characterization of Mixed Ligand Complexes of Zirconium(IV) with Sulphur, Nitrogen and Oxygen Donor Ligands

Luminescent, optical, magnetic and metamaterial behavior of cerium complexes

The complexes of cerium with nitrogen, oxygen and sulfur donor ligands were prepared by conventional method. These newly synthesized complexes were characterized by FTIR, UV–Vis, DART Mass, TGA, PXRD, SEM and TEM techniques. The magnetic studies were carried out by the vibrating sample magnetometer. The optical constants were measured by absorption and reflection spectra as a function of wavelength. The concentration dependence of refractive index and absorption was observed by the experimental method, which reveals that these parameters are affected by change in concentration. The optical band gap obtained from Tauc-plot indicates its probability to be a good semiconductor. The luminescence behavior of these cerium complexes was observed by the absorption and emission spectra and the emission life time was calculated by their life time spectra.

Spectroscopic evidence supporting neutral thiol ligation to ferrous heme iron.

The binding of neutral thiol (ethanethiol, EtSH) or thioether (tetrahydrothiophene, THT) to two types of heme proteins in their ferrous state has been investigated with UV-visible (UV-Vis) absorption and magnetic circular dichroism spectroscopy. For the second GAF (cGMP-specific phosphodiesterases, adenylyl cyclases, and FhlA) domain from the sensory kinase MsmS (sGAF2), stepwise additions of these respective two sulfur-donor ligands to its dithionite-reduced ferrous form generate homogeneous six-coordinate low-spin ferrous complexes at both pHs 7.0 and 5.4. Similar complexes were partially formed for deoxyferrous soybean leghemoglobin with EtSH or THT within their solubility limits in water. The titrations cause significant UV-Vis spectra changes attributable to a five-coordinate to six-coordinate heme iron coordination change. For sGAF2, the resulting spectra are essentially identical for the both ligands, clearly indicating the direct binding of neutral thiol/thioether to ferrous heme iron as the distal ligand. On the other hand, the thiol EtSH binds to ferric sGAF2 in the anionic thiolate form, while thioether THT forms its ferric sGAF2 complex as a neutral ligand. These observations provide compelling evidence that neutral cysteine is a plausible ligand for ferrous heme proteins.

Zinc Bioavailability from Phytate-Rich Foods and Zinc Supplements. Modeling the Effects of Food Components with Oxygen, Nitrogen, and Sulfur Donor Ligands.

Aqueous solubility of zinc phytate (Ksp = (2.6 ± 0.2) × 10-47 mol7/L7), essential for zinc bioavailability from plant foods, was found to decrease with increasing temperature corresponding to ΔHdis of -301 ± 22 kJ/mol and ΔSdis of -1901 ± 72 J/(mol K). Binding of zinc to phytate was found to be exothermic for the stronger binding site and endothermic for the weaker binding site. The solubility of the slightly soluble zinc citrate and insoluble zinc phytate was found to be considerably enhanced by the food components with oxygen donor, nitrogen donor, and sulfur donor ligands. The driving force for the enhanced solubility is mainly due to the complex formation between zinc and the investigated food components rather than ligand exchange and ternary complex formation as revealed by quantum mechanical calculations and isothermal titration calorimetry. Histidine and citrate are promising ligands for improving zinc absorption from phytate-rich foods.

Organo Sn(IV) and Pd(II) complexes with various oxygen and sulphur donor ligands: Synthesis, spectroscopy and biological activity

Two Pd(II) complexes, (HL1CSS)2Pd (1) and (KL2CSS)2Pd (2), were synthesized by stirring 2-(1-piperazinyl)ethanol (HL1H)/l-lysine (HL2H) monohydrate in methanol with KOH, CS2 and PdCl2(aq). Homobimetallic (Sn, Sn) products, Ph3SnL3Sn(Cl)Bu2 (3) and Ph3SnL3SnBu3 (4) were produced by refluxing sodium but-2-ynedioate (Na2L3) with Ph3SnCl and Bu2SnCl2 or Ph3SnCl and Bu3SnCl in methanol. A heteronuclear (Sn,Pd) product, [(Bu3Sn)2L2CSS]2Pd (5) was synthesized by the reaction of 5-aminoisophthalic acid (H2L4H), KOH, CS2, PdCl2(aq) with Bu3SnCl. The products were characterized by elemental analysis, FT-IR, UV-Vis, 1H NMR and EIMS. A square planar geometry of Pd(II) and a penta-coordinated environment around Sn(IV) were verified in solid state. The complexes maintain their solid state geometries around Pd(II) even in solutions. Pd(II) complexes 1 and 2 exhibited a significant intercalating mode of binding with salmon sperm DNA. ALPs were inhibited in a concentration dependent manner. Sn(IV) complexes (3 and 4) were inactive against ALPs. Pd(II) complexes (1 and 2) were potent ALPs inhibitors, while the heteronuclear complex 5 was comparatively less active. Organotin(IV) products demonstrated significant antibacterial/ antifungal potential while Pd(II) products were inactive. The heteronuclear (Sn,Pd) product demonstrated moderate inhibition. Among all products, Pd(II) derivative 1 exhibited the highest hemolytic effect.

Preparation, spectroscopic characterization and antimicrobial activities of mixed metal (Sb and Bi) bridged derivatives with mixed sulfur donor ligands

This article explores the syntheses of six mixed metal derivatives of antimony(III) and bismuth(III) by the reaction of ethane-1,2-dithiol and metal bis derivatives of dithiocarbamates and/or dithiophosphates ligands in 1:1:1 M stoichiometry. These derivatives have been characterized by physicochemical [elemental analysis (C, H, N, S, Sb and Bi), molecular weight and melting point determinations], spectral [UV–Visible, FTIR, NMR (1H, 13C and 31P)], powder X–ray diffraction studies. These derivatives have nano-ranged crystallite size (8.18–18.04 nm) with monoclinic crystal system. All the synthesized derivatives have two metal centers (Sb and Bi) which elevate the zone of inhibition against four bacterial and two fungal species as compared to single metal species (metal precursors) as well as standard drugs.

A polymeric silver thiosaccarinate complex with a two-dimensional triply entangled mesh and argentophilic interactions.

Silver(I) complexes with sulfur-donor ligands have a broad range of pharmacological applications. One of the most important factors for tuning the biological activity is the type of donor atom and the ease of ligand replacement. Silver thiosaccharinates display a wide range of structures from mono- to polynuclear complexes. We report the synthesis, crystal structure and vibrational spectroscopic analysis of a two-dimensional Ag(I)-thiosaccharinate coordination polymer, namely poly[tris(μ2-4,4'-bipyridine-κ(2)N:N')bis(μ3-1,1-dioxo-1,2-benzisothiazole-3-thiolato-κ(3)N:S(3):S(3))bis(μ2-1,1-dioxo-1,2-benzisothiazole-3-thiolato-κ(2)S(3):S(3))tetrasilver(I)], [Ag2(C7H4NO2S2)2(C10H8N2)1.5]n, with 4,4'-bipyridine acting as a spacer. A relevant feature of the structure is the presence of an unusually short Ag...Ag separation of 2.8859 (10) Å, well within the range of argentophilic interactions and confirmed as such by Raman analysis of the low-frequency spectrum. From a topological point of view, the structure presents interpenetration in the form of a threefold entangled 2D→2D mesh (2D is two-dimensional).

Separation of heavy metal from water samples—The study of the synthesis of complex compounds of heavy metal with dithiocarbamates

ABSTRACTThe toxicity and persistence of heavy metal (HM) ions may cause several problems to marine organisms and human beings. For this reason, it is growing the interest in the chemistry of sulphur donor ligands such as dithiocarbamates (DDTC), due to their applications particularly in analytical chemistry sciences. The aim of this work has been the study of heavy metal complexes with DDTC and their application in separation techniques for the preconcentration and/or removing of heavy metals from the water solutions or the water ecosystems prior to their analysis. The HM-DDTC complexes were prepared and characterized by elemental analysis, FTIR and UV-Vis spectroscopic methods. The elemental analysis and the yield of the synthesis (97.5–99.9%) revealed a good purity of the complexes. High values of complex formation yields of HM-DDTC complexes is an important parameter for quantitatively removing/and or preconcentration of heavy metal ions from water solution even at low concentration of heavy metals. Significant differences founded between the characteristic parameters of UV/Vis (λmax and ϵmax) and FTIR absorption spectra of the parent DDTC and HM-DDTC complexes revealed the complex formation. The presence of the peaks at the visible spectral zone is important to M(nd10-m)-L electron charge transfer of the new complexes. The (C=N) (1450–1500 cm−1) and the un-splitting (C–S) band (950–1002 cm−1) in HM-DDTC FTIR spectra are important to the identification of their bidentate mode (HM[S2CNC4H10]2). The total CHCl3 extraction of trace level heavy metals from water samples after their complex formation with DDTC is reported in this article.

Pharmacological Activity of a Few Transition Metal Complexes: A Short Review

Transition metals have an important place within medicinal inorganic chemistry. Transition metals exhibit different oxidation states and can interact with a number of negatively charged molecules. This activity of transition metals led to the recent development of drugs which are based on metals and are considered to be potential candidates for pharmacological and therapeutic applications. This review focuses on research undertaken over the past few decades which has sought to possess preclinical pharmacological screenings like anti-microbial, anti-inflammatory and anti-tumor action of synthetic transition metal complexes. It concentrates primarily on a limited number of first row transition metal complexes particularly V(IV), Co(II), Ni(II), Cu(II) and Zn(II) complexes and traces the pharmacological applications of these coordination compounds. In the first part, the nitrogen, oxygen and sulfur donor ligands chelating to transition metals used in metallodrugs are described. The second part describes the pre-clinical screenings viz., anti-microbial, anti-inflammatory and anti-tumor responses of the above coordination compounds incorporating these nitrogen, oxygen and sulfur donor ligands. This survey encourages further research in this field for future applications.

Diiron bridged-thiolate complexes that bind N2 at the Fe(II)Fe(II), Fe(II)Fe(I), and Fe(I)Fe(I) redox states.

All known nitrogenase cofactors are rich in both sulfur and iron and are presumed capable of binding and reducing N2. Nonetheless, synthetic examples of transition metal model complexes that bind N2 and also feature sulfur donor ligands remain scarce. We report herein an unusual series of low-valent diiron complexes featuring thiolate and dinitrogen ligands. A new binucleating ligand scaffold is introduced that supports an Fe(μ-SAr)Fe diiron subunit that coordinates dinitrogen (N2-Fe(μ-SAr)Fe-N2) across at least three oxidation states (Fe(II)Fe(II), Fe(II)Fe(I), and Fe(I)Fe(I)). The (N2-Fe(μ-SAr)Fe-N2) system undergoes reduction of the bound N2 to produce NH3 (∼50% yield) and can efficiently catalyze the disproportionation of N2H4 to NH3 and N2. The present scaffold also supports dinitrogen binding concomitant with hydride as a co-ligand. Synthetic model complexes of these types are desirable to ultimately constrain hypotheses regarding Fe-mediated nitrogen fixation in synthetic and biological systems.