Iron Coordination Compounds Research Articles

Mitigating methylglyoxal-induced glycation stress: the protective role of iron, copper, and manganese coordination compounds in Saccharomyces cerevisiae.

Glycation-induced stress (G-iS) is a physiological phenomenon that leads to the formation of advanced glycation end-products, triggering detrimental effects such as oxidative stress, inflammation, and damage to intracellular structures, tissues, and organs. This process is particularly relevant because it has been associated with various human pathologies, including cancer, neurodegenerative diseases, and diabetes. As therapeutic alternatives, coordination compounds with antioxidant activity show promising potential due to their versatility in attenuating oxidative stress and inflammation. Herein, we investigated the antioxidant-related protective potential of a series of complexes: [Cu(II)(BMPA)Cl2] (1), [Fe(III)(BMPA)Cl3] (2), and [Cl(BMPA)MnII-(μ-Cl)2-MnII(BMPA)-(μ-Cl)- MnII(BMPA)(Cl)2]•5H2O (3), all synthesized with the ligand bis-(2-pyridylmethyl)amine (BMPA) in Saccharomyces cerevisiae exposed to G-iS caused by methylglyoxal (MG). Pre- treatment with complexes 1-3 proved highly effective, increasing yeast tolerance to G-iS and attenuating mitochondrial dysfunction. This observed phenotype appears to result from a reduction in intracellular oxidation, lipid peroxidation levels, and glycation. Additionally, an increase in the activity of the antioxidant enzymes superoxide dismutase and catalase was observed following treatment with complexes 1-3. Notably, although complexes 1-3 provided significant protection against oxidative stress induced by H2O2 and menadione, their protective role was more effective against MG-induced glycation stress. Our results indicate that these complexes possess both antiglycation and antioxidant properties, warranting further investigation as potential interventions for mitigating glycation and oxidative stress-related pathologies.

Synthesis and physicochemical studies of iron(III) complex compounds with TSC

The authors developed methods for the synthesis of coordination compounds of iron(III) with thiosemicarbazide (TSC).The compounds structure was proved by IR spectroscopy, conductometry, X-ray diffraction, and thermogravimetry. The authors found the bidentate coordination of TSC with iron(III) via sulphur and nitrogen atoms. Thermogravimetrically authors have established the proceeding of the complex decomposition in two stages. The first stage involves thermolysis of organic ligands with the formation of the corresponding iron salts; the second one includes decomposition of iron salts and formation of iron(III) oxide. Conductometrically we have established the synthesised complexes are strong electrolytes. X-ray diffraction shows the crystallisation of the complexes into orthorhombic syngonies. There are two structural units in the cell.

Experimental and DFT Study of Monensinate and Salinomycinate Complexes Containing {Fe3(µ3-O)}7+ Core.

Two trinuclear oxo-centred iron(III) coordination compounds of monensic and salinomycinic acids (HL) were synthesized and their spectral properties were studied using physicochemical/thermal methods (FT-IR, TG-DTA, TG-MS, EPR, Mössbauer spectroscopy, powder XRD) and elemental analysis. The data suggested the formation of [Fe3(µ3-O)L3(OH)4] and the probable complex structures were modelled using the DFT method. The computed spectral parameters of the optimized constructs were compared to the experimentally measured ones. In each complex, three metal centres were joined together at the axial position by a μ3-O unit to form a {Fe3O}7+ core. The antibiotics monoanions served as bidentate ligands through the carboxylate and hydroxyl groups located at the termini. The carboxylate moieties played a dual role bridging each two metal centres. Hydroxide anions secured the overall neutral character of the coordination species. Mössbauer spectra displayed asymmetric quadrupole doublets that were consistent with the existence of two types of high-spin iron(III) sites with different environments-two Fe[O5] and one Fe[O6] centres. The solid-state EPR studies confirmed the +3 oxidation state of iron with a total spin St = 5/2 per trinuclear cluster. The studied complexes are the first iron(III) coordination compounds of monensin and salinomycin reported so far.

Syntheses and structural studies of iron(III) coordination compounds with pontential spin-crossover applications

Syntheses and structural studies of iron(III) coordination compounds with pontential spin-crossover applications

Expanded Ligands Based upon Iron(II) Coordination Compounds of Asymmetrical Bis(terpyridine) Domains.

The synthesis and characterization of two tritopic ligands containing a 2,2':6',2″-terpyridine (tpy) metal binding domain and either a 3,2':6',3″- or a 4,2':6',4″-tpy domain are detailed. The synthetic routes to these ligands involved the [Pd(dppf)Cl2]-catalyzed coupling of a boronic ester-functionalized 2,2':6',2″-tpy with bromo-derivatives of 3,2':6',3″-tpy or 4,2':6',4″-tpy. The 2,2':6',2″-tpy domains of the tritopic ligands preferentially bind Fe2+ in reactions with iron(II) salts leading to the formation of two homoleptic iron(II) complexes containing two peripheral 3,2':6',3″-tpy or 4,2':6',4″-tpy metal-binding sites, respectively. These iron(II) complexes are potentially tetratopic ligands and represent expanded versions of tetra(pyridin-4-yl)pyrazine.

Hybrid Polymer Composite of Prussian Red Doped Polythiophene for Adsorptive Wastewater Treatment Application.

Coordination compounds as dopants to conducting polymers combine desirable properties of individual components for a synergistic effect. Prussian red (PR) a low spin iron (III) coordination compound was doped in polythiophene (PTP) matrix to explore propensity of this inorganic-organic hybrid composite material towards wastewater treatment. PR doping was observed to improve mechano, thermal, electrical, and photocatalytic attributes of pure PTP. PTP/PR composite characterization was attempted using the powder X-ray diffraction, TEM, TGA, FTIR, BET analysis and UV-Visible spectroscopy. Optimization of adsorption conditions, adsorbent regeneration, adsorption thermodynamics studies of PTP/PR were carried out using malachite green (MG) dye as a model system. Under optimized conditions 92% MG dye adsorption was observed over 20 mg PTP/PR nanocomposite in 20 minutes at pH 7. PTP/PR nanocomposite also demonstrated a complimentary performance with real wastewater samples. Thermodynamic studies indicate spontaneous process with electrostatic attraction as the predominant noncovalent interaction. This study highlights designing catalysts capable of synergistic adsorption and photocatalytic activities for effective wastewater treatment.

Near to neutral pH all-iron redox flow battery based on environmentally compatible coordination compounds

We demonstrate a redox flow battery at a near to neutral of pH 8.6 using nontoxic iron-coordination compounds as redox carriers in both negative and positive electrolytes. The negative electrolyte contains a compound commercially in use as fertilizer, the racemic form of iron(III)-N,N’-ethylene-bis-(o-hydroxyphenylglycine), with a reduction potential of -613 mV vs Ag/AgCl, 1 M NaCl. The positive electrolyte contains sodium ferrocyanide, with a reduction potential of +235 mV vs Ag/AgCl, 3 M KCl. The all-iron aqueous redox flow cell exhibits a cell voltage of 848 mV at 50% state-of-charge (SOC). The solubility for both reactants in this work was up to ∼0.2 M. Permeation experiments were performed with three different cation exchange membranes: the Nafion membranes NR-212 and N-324, and the low-cost sulfonated poly(ether ketone) SPEEK membranes. A capacity retention of nearly 100% over 75 charge discharge cycles was achieved with the N-324 membrane. No significant decay in capacity or voltage efficiency was observed during two days of cycling at low 14% and high 93% SoC limits. Using a low-cost sulfonated poly(ether ketone) (SPEEK) membrane, a good capacity utilization of 86.5% was demonstrated at a voltage efficiency of 81.5% at 25 mA cm–2 current density, and a peak power density of 44.5 mW cm–2 was achieved at 95 mA cm–2 current density. However, crossover was detected. Reactant crossover at N-324 and SPEEK membranes was 5·10–12 cm2 s–1 and 6.2·10–11 cm2 s–1, respectively. The new combination of nontoxic iron complexes represents a promising option for stationary environmentally friendly energy storage applications.

High-Temperature Spin Crossover in Iron(II) Complexes with 2,6-Bis(1H-imidazol-2-yl)pyridine

Novel iron(II) coordination compounds containing a ligand 2,6-bis(1H-imidazol-2-yl)pyridine (L), having such a composition as [FeL2]SO4·0.5H2O, [FeL2]Br2·H2O, [FeL2](ReO4)2, [FeL2]B10H10∙H2O, [FeL2]B12H12∙1.5H2O had been synthesized and studied using UV-Vis (diffuse reflectance), infrared, extended X-ray absorption fine structure (EXAFS), and Mössbauer spectroscopy methods, as well as X-ray diffraction and static magnetic susceptibility methods. The analysis of the μeff(T) dependence in the temperature range of 80–600 K have shown that all the obtained complexes exhibit a high-temperature spin crossover 1A1 ↔ 5T2.

Study of Spin-Crossover in Iron(II) Complexes with 2,6-Bis(4,5-Dimethyl-1H-Imidazol-2-yl)Pyridine and closo-Borate Anions

New iron(II) coordination compounds with 2,6-bis(4,5-dimethyl-1H-imidazol-2-yl)pyridine (L) and closo-borate(2–) anions [FeL2]B10H10⋅2H2O and [FeL2]B12H12⋅H2O have been synthesized. The compounds have been identified and studied by CHN analysis, electron spectroscopy (diffuse reflection spectroscopy), IR, Mössbauer, and EXAFS spectroscopies, X-ray powder diffraction, and static magnetic susceptibility. The structures of the coordination knots of complexes [FeL2]B10H10⋅2H2O and [FeL2]B12H12⋅H2O has been obtained by modeling the EXAFS spectra. The ligand is coordinated by the iron(II) ion in a tridentate-cyclic manner by two nitrogen atoms of imidazole cycles and a nitrogen atom of pyridine to form the FeN6 coordination knot. The study of the temperature dependence of the magnetic susceptibility in the range of 80–500 K has showed that the high-temperature spin-crossover 1А1 ↔ 5Т2 manifests itself in the obtained compounds.

Spin crossover in iron(II) complexes with new ligand 2,6-bis(4,5-dimethyl-1H-imidazole-2-yl)pyridine

Iron(II) coordination compounds containing a new ligand, 2,6-bis(4,5-dimethyl-1H-imidazol-2-yl)pyridine (L), of composition [FeL2](NO3)2·H2O (1·H2O), [FeL2](ClO4)2·0.5H2O (2·0.5H2O), [FeL2]SO4·0.5H2O (3·0.5H2O), or [FeL2](ReO4)2·2H2O (4·2H2O) have been synthesized and studied by UV–vis (diffuse reflectance), infrared, extended X-ray absorption fine structure (EXAFS), and Mössbauer spectroscopies, as well as X-ray diffraction and static magnetic susceptibility methods. The structure of a copper(II) complex with L of composition [CuL2]SO4·3H2O has been successfully determined. The analysis of the μeff(T) dependence in the temperature range of 80–520 K showed that complexes [FeL2](NO3)2·H2O, [FeL2](ClO4)2·0.5H2O, and [FeL2](ReO4)2·2H2O and their dehydrated counterparts are subject to high-temperature spin crossover 1A1 ↔ 5T2.

Synthesis and Properties of Iron(II) and Copper(II) Coordination Compounds with 2,6-Bis[1-(phenylimino)ethyl]pyridine

Synthesis and Properties of Iron(II) and Copper(II) Coordination Compounds with 2,6-Bis[1-(phenylimino)ethyl]pyridine

Visible light-driven photocatalyst: An iron(III) coordination compound in Rhodamine B degradation

Rhodamine B (RhB) was photocatalytically degraded by an iron(III) complex (FeL3, L = Methyl 3-hydroxy-2-propenedithioate). The photocatalysts were synthesized, supported on glass slides, and characterized by elemental analyses, IR, UV–vis, Raman, TGA, XPS, Diffuse Reflectance spectroscopy, and Powder X-ray diffraction analyses. The iron complex was also impregnated onto titania (TiO2) films to enhance the photocatalytic performance of this oxide. The structure of the complex does not change when supported on a glass substrate. The FeL3 showed a band gap value (Eg = 1.32 eV) lower than TiO2 (Eg = 3.38 eV), whereas the FeL3 sensitized titania showed the highest Eg value (Eg = 3.41 eV). The photocatalytic degradation of RhB by the TiO2-FeL3 system (27%) after 180 min of reaction slightly improves the performance of TiO2 (22%). Remarkably, FeL3 film showed the best performance (34%). When using scavengers, the degradation reveals that the produced superoxide radicals seem to be responsible for the RhB degradation.

Electrochemical studies of iron(II) complexeswith 4‐amino‐1,2,4‐triazole possessing spin crossover

AbstractThe electrochemical properties of a number of coordination compounds of iron(II) with 4‐amino‐1,2,4‐triazole (NH2trz), which have a sharp thermally induced spin crossover with hysteresis on the temperature curves of the effective magnetic moment dependence, were studied using method cyclic voltammetry (CV) at 298 K. The complexes were mixed with carbon powder and silicon oil and included in the paste electrode. The measurements were made in solutions of 0.10 M KNO3. It was found that the area 0.5–0.6 V and 0.3–0.4 V contains the anode and cathode current peaks of freshly prepared paste electrodes. In all cases, the redox process in the paste is quasi‐reversible. At the same molar concentration of complexes in the paste (0.1 mol kg−1), a number of current peaks depends on the nature of the anion. The peak current value correlates with the calculated fraction of the high spin form in the solid phase of the complex and the temperature of the direct spin crossover (when heated, Tc↑). The magnetic properties of Fe(NH2trz)3(NO3)2 complex, its mixture with carbon powder and the paste were measured by Faraday method in a temperature range 80–370 K. The effective magnetic moment was depended on changes in variations in the environment of the molecules of the complex in the studied samples.

Iron(II) spin crossover complexes with a sulfur rich ligand backbone

One goal that many scientists pursue is the unification of several interesting chemical or physical properties in one system, as only multifunctional materials will meet the challenges of today's technologies. With this background, three novel iron(II) coordination compounds with a Schiff base-like N2O2 coordinating ligand L bearing a sulfur-rich backbone are investigated in this work. Two of the complexes, the mononuclear [FeL(py)2] (py = pyridine) and the coordination polymer {[FeL(bpee)]}n [bpee = trans-1,2-bis(4-pyridyl)ethene], show spin crossover behavior followed using magnetic susceptibility measurements and Mössbauer spectroscopy. To get a closer insight into different states of the complex spin crossover behavior of {[FeL(bpee)]}n, XPS measurements were conducted at different temperatures. Furthermore, impedance spectroscopic measurements at variable temperatures were performed to get insight into the electrical conductivity of this system. All iron(II) complexes were electrochemically characterized using cyclovoltammetric measurements, supplemented by DFT computation. Apparently, the extension by a sulfur backbone leads to a stabilization of the HOMO. Due to this, the complexes are more difficult to oxidize than comparable systems. With {[FeL(azpy)]}n, another coordination polymer, this time axially decorated by the redox-active ligand azpy (azpy = 4,4′-azopyridine), is investigated, which is, however, a pure high spin complex.

Insights into the naphthalenide-driven synthesis and reactivity of zerovalent iron nanoparticles.

The chemical and thermal stability of alkali metal naphthalenides as powerful reducing agents are examined, including the type of alkali metal ([LiNaph] and [NaNaph]), the type of solvent (THF, DME), the temperature (-30 to +50 °C), and the time of storage (0 to 12 hours). The stability and concentration of [LiNaph]/[NaNaph] are quantified via UV-Vis spectroscopy and the Lambert-Beer law. As a result, the solutions of [LiNaph] in THF at low temperature turn out to be most stable. The decomposition can be related to a reductive polymerization of the solvent. The most stable [LiNaph] solutions in THF are exemplarily used to prepare reactive zerovalent iron nanoparticles, 2.3 ± 0.3 nm in size, by reduction of FeCl3 in THF. Finally, the influence of [LiNaph] and/or remains of the starting materials and solvents upon controlled oxidation of the as-prepared Fe(0) nanoparticles with iodine in the presence of selected ligands is evaluated and results in four novel, single-crystalline iron compounds ([FeI2(MeOH)2], ([MePPh3][FeI3(Ph3P)])4·PPh3·6C7H8, [FeI2(PPh3)2], and [FeI2(18-crown-6)]). Accordingly, reactive Fe(0) nanoparticles can be obtained in the liquid phase via [LiNaph]-driven reduction and instantaneously reacted to give new compounds without remains of the initial reduction (e.g. LiCl, naphthalene, and THF).

Harnessing Interfacial Electron Transfer in Redox Flow Batteries

Summary Redox flow batteries (RFBs) have garnered increasing attention for their potential to enable the widespread adoption of renewable electricity. However, a critical need associated with the continued development of this technology involves designing electrode-electrolyte interfaces that exhibit rapid, stable electron transfer kinetics. This targeted review outlines key challenges associated with measuring and enhancing the electron transfer kinetics of established and emerging flow battery active materials. We discuss several promising opportunities for advancing flow battery science and technology using the tools of applied electroanalysis and catalysis science. These challenges and opportunities are broadly relevant for future research directed at advancing the commercial adoption of RFBs for grid-scale energy storage.

Spin Crossover in New Iron(II) Coordination Compounds with Tris(pyrazol-1-yl)Methane

We review here new advances in the synthesis and investigation of iron(II) coordination compounds with tris(pyrazol-1-yl)methane and its derivatives as ligands. The complexes demonstrate thermally induced spin crossover accompanied by thermochromism. Factors that influence the nature and temperature of the spin crossover are discussed.

Iron(III), cobalt(II) and zinc(II) coordination compounds with a carboximidamide ligand: Synthesis, structures and properties

Coordination complexes of iron(III), cobalt(II) and zinc(II) with the ligand N′-{[1-(pyridin-2-yl)ethylidene]amino}pyridine-2-carboximidamide (pmhpa) have been synthesised and were structurally characterized by elemental analysis, mass spectrometry, X-ray diffraction and infrared spectroscopy. The mononuclear iron(III) complex, [Fe(pmhap)2][FeCl4], (1), adopts the orthorhombic non-centric space group P212121. The iron is present in an octahedral environment in the ion [Fe(pmhap)2]+. The crystallographically-determined formula of the cobalt(II) complex (2) is [Co2(pmhap)2Cl3]2[CoCl4].4MeOH. The compound crystallizes in the non-centric space group P4̄21c with a single cobalt ion in the asymmetric unit. The complex is dinuclear, with two cobalt ions bridged by chloride and the two nitrogen atoms of N=N of the pmhap ligand. The zinc(II) complex; [Zn2(pmhpa)3](NO3)4.2.75MeOH (3) crystallizes in the cubic space group Pa3̄ with disordered methanol molecules present. This is dinuclear with the two zinc atoms being bridged by three N=N links from the ligand to form a threefold symmetric rotor. Infrared spectroscopy confirms that coordination occurs through the azide bridge. Measurements of magnetic susceptibility for the iron(III) and cobalt(II) complexes show that they are paramagnetic between 5 and 300 K. Mössbauer spectroscopic data supports the structure of the iron(III) complex being composed of an octahedral and a tetrahedral iron atom.

Iron(II) Spin Crossover Complexes Based on a Redox Active Equatorial Schiff-Base-Like Ligand.

In this work, two iron(II) coordination compounds with a N2O2 coordinating Schiff base-like ligand bearing a redox active tetrathiafulvalene (TTF) unit and pyridine or trans-1,2-bis(4-pyridylethylene) as an axial ligand are synthesized. Crystals suitable for single X-ray structure analysis were obtained for the new ligand. The complexes were characterized by magnetic susceptibility measurements, T-dependent UV-vis spectroscopy, and cyclic voltammetry. Both complexes display spin transition behavior below room temperature with T1/2 values of 146 and 156 K. The mononuclear iron(II) complex [FeTTFL(py)2] is relatively stable up to 400 K compared to similar complexes, showing no loss of axial ligands upon heating. Temperature dependent Mössbauer spectroscopy was conducted for the coordination polymer {[FeTTFL(bpee)]}n to get more information regarding the origin of the stepwise spin crossover (SCO) behavior observed in the magnetic measurements. The change of the spin state is accompanied by a change of the optical properties, which can be monitored by VT-UV-vis spectroscopy for the mononuclear complex and has been analyzed in theoretical studies. The redox behavior of the iron(II) complexes reveals three reversible redox steps which are located at the iron center and at the TTF unit of the ligand. Oxidation of the TTF unit induces characteristic changes in the UV-vis spectrum that can be followed by spectroelectrochemical UV-vis spectroscopy. Addressing the potential of the iron-centered redox process results in similar changes in the UV-vis spectrum, which indicates an electronic coupling of the redox active unit with the metal center under certain circumstances.

Synthesis, Structure and Biological Activity of Coordination Compounds of Copper, Nickel, Cobalt, and Iron with Ethyl N'-(2-Hydroxybenzylidene)-N-prop-2-en-1-ylcarbamohydrazonothioate

N-(Prop-2-en-1-yl)hydrazonocarbothioamide reacts with iodoethane in methanol with further addition of 2-hydroxybenzaldehyde to form hydroiodide of carbamohydrazonothioate (HL·HI). The coordination compounds were obtained by interaction of HL or HL·HI with copper, nickel, cobalt and iron salts CuLХ·nH2O [X = Cl–, Br–, NO3–; n = 0–1], Ni(L)2·HI·CH3OH, Сo(L)2X [X = I–, NO3–] and Fe(L)2NO3. The structures of three complexes were established by single crystal X-ray analysis. The synthesized complexes exhibit selective antimicrobial and antifungal activity against a series of standard microorganisms and fungi in the concentration range of 30–500 μg/mL. In addition, nickel and iron complexes selectively inhibit the growth and proliferation of cancer cells and do not adversely affect normal cells.