Iron Metal Complexes Research Articles

Accelerated Iron Evolution in Quaternary Red Soils through Anthropogenic Land Use Activities

Iron in soil exists in various valence states and is prone to changes with alterations in soil environmental conditions. Its migration and transformation are crucial for soil formation and understanding soil evolution. This study focuses on Quaternary red soils found in woodland, sparse forest grassland, grassland, and cultivated land located in the semi-humid region of the middle temperate zone. For comparison, buried Quaternary red soil was also examined. A soil reconstruction model was used to quantitatively calculate the variation of different forms of iron in order to analyze various forms of iron composition, migration, and transformation within the soil profile, as well as the evolutionary traits of Quaternary red soils influenced by diverse land use activities. This study found that after exposure and use, iron from the topsoil of buried Quaternary red soil migrated to the subsoil, altering the iron distribution. Free iron and crystalline oxides decreased in the topsoil but increased in specific subsoil layers, with woodland and grassland showing the most significant changes. Silicate-bound iron pooled in the soil weathered to form free iron under different land uses, and poorly crystalline iron oxides transformed into crystalline oxides, with grassland exhibiting the highest transformation intensity. Conversion processes predominated over iron migration in the Quaternary red soils. The evolution of Quaternary red soils can be divided into three stages, marked by changes in iron composition and crystallization due to anthropogenic land use activities. Initially, during 140−94 ka BP, iron composition was stable. Then, between 94–24 ka BP, plant decomposition formed iron–metal complexes, releasing and crystallizing poorly crystalline iron oxides. Finally, from 24 ka BP to the present, anthropogenic activities intensified, increasing the formation and conversion rates of these oxides. This study quantifies iron migration and transformation in Quaternary red soils, providing insights for sustainable soil management, especially in regions where human activities have accelerated iron evolution. Based on these findings, the following policy recommendations are proposed: implement sustainable land use practices, encourage land management strategies that preserve natural vegetation, promote research on soil management techniques, develop and implement regulatory policies, and support educational programs to maintain the health and stability of Quaternary red soils, particularly in regions prone to accelerated iron evolution due to anthropogenic activities.

Fe3+-modified polyamide membrane with a porous network structure: Rapid permeation and efficient interception of trace organic compounds

Forward osmosis (FO) is a promising technology in the treatment of trace organic substances. However, the development of this technology is limited by membrane material selection and the long-term chemical stability and durability of the membrane. Whereas ibuprofen, a representative trace organic substances that is hydrophobic and negatively charged, poses potential environmental hazards due to its bioactivity. In this work, polyethersulfone (PES) membranes were modified with iron metal complexes via chelation reactions to achieve high rejection rates for ibuprofen. The Fe3+-modified composite FO membrane increased the ibuprofen rejection rate to 98.3 % compared to less than 80.0 % for the original PES membrane. Additionally, the modified membrane enhanced water flux by at least 25.0 % and reduced reverse solute flux to a maximum of 73.0 % of that of the polyamide composite membrane, while significantly improving anti-fouling capabilities. Membrane characterization results revealed that the significant enhancement in the ibuprofen retention rate was due to the addition of a negative charge by forming complexes with Fe3+, which increased intermolecular interactions. Additionally, the dense network structure developed by the Fe3+-EDTA-2Na modification also contributed to the enhanced membrane performance.

Electron transfer catalysis mediated by 3d complexes of redox non-innocent ligands possessing an azo function: a perspective.

It was first reported almost two decades ago that ligands with azo functions are capable of accepting electron(s) upon coordination to produce azo-anion radical complexes, thereby exhibiting redox non-innocence. Over the past two decades, there have been numerous reports of such complexes along with their structures and diverse characteristics. The ability of a coordinated azo function to accept one or more electron(s), thereby acting as an electron reservoir, is currently employed to carry out electron transfer catalysis since they can undergo redox transformation at mild potentials due to the presence of energetically accessible energy levels. The cooperative involvement of redox non-innocent ligand(s) containing an azo group and the coordinated metal centre can adjust and modulate the Lewis acidity of the latter through selective ligand-centred redox events, thereby manipulating the capacity of the metal centre to bind to the substrate. We have summarized the list of first row transition metal complexes of iron, cobalt, nickel, copper and zinc with redox non-innocent ligands incorporating an azo function that have been exploited as electron transfer catalysts to effectuate sustainable synthesis of a wide variety of useful chemicals. These include ketazines, pyrimidines, benzothiazole, benzoxazoles, N-acyl hydrazones, quinazoline-4(3)H-ones, C-3 alkylated indoles, N-alkylated anilines and N-alkylated heteroamines. The reaction pathways, as demonstrated by catalytic loops, reveal that the azo function of a coordinated ligand can act as an electron sink in the initial steps to bring about alcohol oxidation and thereafter, they serve as an electron pool to produce the final products either via HAT or PCET processes.

Quercetin Zinc and Iron Metal Complexes Protect against Sodium Arsenite Intoxication in the Hepato-Renal System of Wistar Rats via the Oxidative Stress Pathway.

Chronic exposure to arsenic is a major health concern consequent upon generation of excessive reactive oxygen species. The safety of treatment with chelating agents has not been well established; therefore, there is a need for a paradigm shift in the approach to management of arsenic toxicity. Bioflavonoids are known to influence redox homeostasis in cells; the study therefore investigates the efficacy of quercetin and its zinc and iron metal complexes on sodium arsenite (NaAr)-intoxication in rats. Spectroscopic study of quercetin hydrate and its metal complexes was performed using UV-Vis and FT-IR spectrometer. Furthermore, twenty male Wistar rats were obtained and equally divided into four groups, treated orally and daily for 28 days with 10 mg/kg NaAr, 30 mg/kg quercetin, quercetin-zinc, and quercetin-iron separately. Five more rats were used as control. Plasmatic aspartate transferase (AST), alanine transferase (ALT), creatinine (CREA), and total protein (TP) were estimated. Levels of kidney and liver lipid peroxidation (LPO), glutathione (GSH), catalase (CAT), and glutathione-S-transferase (GST) were determined. Histology was used to view the lesions. Treatment of arsenic-toxicity with quercetin and its complexes decreased the activities of ALT, AST, CREA, TP, CAT, and GST and concentration of LPO and GSH. Quercetin-zn treatment showed a better result than quercetin-iron in the liver. Histology results showed absence of lesions in quercetin zinc and iron treatment in both the kidney and the liver. Quercetin zinc and iron increased the bioavailability of quercetin and therefore could be relevant as adjuvants in arsenic poisoning.

Coordination chemistry of hepta-tert-butylnonaphosphane.

Hepta-tert-butylnonaphosphane {cyclo-(P4tBu3)}2PtBu was employed as a ligand in transition metal complexes of iron(0) (1), cobalt(-I) (2), copper(I) (3) and rhodium(I) (4), which are readily formed in moderate to good yields, and an unstable palladium(II) complex (5). The ligand features three different bonding modes (one monodentate (compounds 1 and 2) and two bidentate (compounds 3-5) with formation of four- or six-membered chelate rings), as determined by X-ray diffraction studies. The 31P{1H} NMR spectral data of 1-3 have been determined by automated line-shape analysis.

The transition metal complexes of Fe(II), Ni(II) and Cu(II) derived from phthalazine based ligands: Synthesis, crystal structures and biological activities

Twelve metal complexes of Iron(II), Nickel(II) and Copper(II) have been synthesized in 1:1 and 1:2 molar ratio from new phthalazine based ligands (E)-2-(phthalazin-1-yl)-1-(1-(pyridin-2-yl)ethylidene)hydrazine (L1) and (E)-2-(phthalazin-1-yl)-1-((pyridin-2-yl)methylene)hydrazine (L2). The compounds have been characterized by UV-Visible, FT-IR, 1H-NMR, LC-MS/ESI-MS spectroscopic techniqueas well as conductivity measurements and finally structures of some of the compounds have been confirmed through single crystal X-ray crystallographic technique. Crystal data for [Cu(II)L1Cl](2) complex: C15H12ClCuN5, triclinic, Space group P-1, a = 10.5114(11) Å, b= 10.7962(11) Å, c = 13.7510(14) Å, α = 74.206(9)°, β = 71.981(9)°, γ = 84.122(8)° and Z = 1, final R1 was 0.0553(I > 2σ(I)) and wR2 was 0.1892(all data). Crystal data for [Ni(II)(L1)2](ClO4)2(7) complex: C30H26Cl2N10NiO8, monoclinic, Space group P21/n, a = 13.0740(7) Å, b = 19.1326(10) Å, c = 14.5808(9) Å, α = 90°, β = 104.511(6)°, γ = 90°, V = 3530.9(4) Å3, Z = 4, final R1 was 0.0778 (I > 2σ(I)) and wR2 was 0.2226 (all data). Crystal data for [(L2)2(μ-Cl)Cu2(II)]Cl(10) complex: C28H22Cl2Cu2N10, triclinic, Space group P-1, a = 7.7441(15) Å, b = 14.954(3) Å, c = 15.004(3) Å, α = 92.458(11)°, β = 96.234(11)°, γ = 96.291(12)° and Z = 2, final R1 was 0.0576(I > 2σ(I)) and wR2 was 0.1671(all data). Crystal data for [Ni(II)(L2)2](ClO4)2(14) complex: C28H22N10O8Cl2Ni, monoclinic, Space group P21/c, a = 13.1220(12) Å, b = 11.3216(10) Å, c = 23.982(2) Å, α = 90°, β = 104.621(4)°, γ = 90° and Z = 4, final R1was 0.0931(I > 2σ(I)) and wR2 was 0.3083 (all data). The compounds were investigated for their antimicrobial, antioxidant and DNA cleavage activities.

Second-order NLO properties and two-state switching effects of transition metal redox complexes of iron and cobalt: A DFT study

Designing switchable materials with large contrasts of nonlinear optical properties has been the focus of research in recent decades because of their widespread applications. Redox-active metal complexes due to charge transfer excitation are suitable to produce switchable nonlinear optical (NLO) material. In this regard, we present here the redox switchable NLO response of active metal complexes of iron and cobalt. The geometric, electronic, molecular absorption, nonlinear optical properties, and switch “ON/OFF” style of these metal complexes are studied at the CAM-B3LYP/6-31 + G(d) level of theory. NLO responses of these redox metal complexes are described in terms of change in the charge transfer (CT) patterns by time dependent density functional theory (TD-DFT). The highest βo value of 301534 × 10−30 esu is noticed in [Fe-ethynyl-ZnP]1+ complex, because of obvious charge transfer transition from metal to ligand i.e meatal-ligand charge transfer (MLCT) in redox metal complex. In each redox metal isomeric pair, the greater hyperpolarizability value of individual isomer is quite consistent with its smaller energy gap (H-Lgap) between highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), low crucial excitation energy, and bathochromic shift of λmax. The remarkable βo contrasts of these isomeric redox complexes illustrate that they can be appropriate for effective redox-triggered NLO switches. Thus, the results reveal that these redox pair complexes show two-state switching “ON/OFF” effect.

RADICAL INITIATED COPOLYMERIZATION OF METHYL METHACRYLATE AND ACRYLONITRILE IN PRESENCE OF IRON COMPLEXES

This article represents data on the effect of organometallic iron complexes: ferrocene, dicarbonyl dimer of cyclopentadienyl iron and tricarbonyl cyclooctatetraene iron on the copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) initiated by benzoyl peroxide. It is shown that the introduction of metal complexes and their structure affect the initial rate of copolymerization, the form of the diagrams of the composition of the obtained copolymers, and the values of the effective constants of the relative activities of the comonomers in the copolymerization of methyl methacrylate and acrylonitrile (system metallocomplex of iron – peroxide benzoyl: ferrocene – peroxide benzoyl: rММА = 1.58; rАН= 0.08 in 60 °С; rММА = 1.30; rАН = 0.05 in 50 °С; dicarbonyl dimer cyclopentadienyl iron–peroxide benzoyl: rММА = 1.36; rАН = 0.06 in 60 °С; rММА = 1.09; rАН = 0.14 in 50 °С; tricarbonyl cyclooctatetraene iron -peroxide benzoyl: rММА = 1.08; rАН = 0.15 in 60 °С; rММА = 1.14; rАН = 0.05 in 50 °С; peroxide benzoyl: rММА = 1.11; rАН = 0.07 in 60 °С; rММА = 1.11; rАН = 0.07 in 50 °С). The proportions of triadic sequences of units in copolymers, experimentally determined from 1H NMR spectroscopy, are given, as well as the calculated proportions of dyads. The presence of iron metal complexes affects the distribution of the proportions of the triad and dyad sequences of units, as well as their microstructure in copolymers. These changes are explained by the formation of macromolecules, both with the participation of free radicals and the stereospecific coordination active centers of polymerization that are formed in the presence of iron complexes.

Computational mechanistic study on molecular catalysis of water oxidation by cyclam ligand-based iron complex

The iron metal complexes containing cyclam-based macrocyclic ligands are active water oxidation catalysts, which can facilitate oxygen–oxygen bond formation during the water-splitting process. To understand the mechanism of the catalytic process, we explored this process by [Fe(cyclam)Cl2]Cl performing density functional theory-based first-principles calculations. We examined the energetics of the formation of the oxygen–oxygen bond through the investigation of complexes [FeV(cyclam)(O)2]+, and [FeV(cyclam)(OH)(O)]+2. The process of water nucleophilic addition by this FeV–(oxo) complexes was explored in detail. Our computational study confirms the formation of these species, which were reported earlier in experimental conditions. The transition states for various reactions of the catalytic cycle were obtained within the implicit water model. From these calculations, we find that the proton transfers to cis–oxo or hydroxide moiety require high activation energy during the formation of the oxygen–oxygen bond. Our calculations reveal that the oxygen–oxygen bond formation by the transfer of a proton to the explicit water molecule requires more activation free energy than the transfer of a proton to the cis–oxo or hydroxide of the FeV–oxo species. Overall [FeV(cyclam)(O)2]+ and [FeV(cyclam)(OH)(O)]+2 species with one explicit water molecule requires similar free energy. The Mulliken spin density data confirm the formation of the superoxide complexes. The activation free energy for the release of the oxygen molecule is lesser than that of the oxygen–oxygen bond formation. The natural bond orbital analysis for the complexes before and after the formation of the oxygen–oxygen bond formation shows that this bond formation happens through the interaction of antibonding orbital, π*(d2 −2 –2py) of Fe=O moiety, with the σ*–orbital of the hydroxide group of the water molecule.

Studies on structural and biological aspects of active oxygen donor ligands oxazolines and iron metal complexes

Studies on structural and biological aspects of active oxygen donor ligands oxazolines and iron metal complexes

Iron Metal Complexes as Catalysts for the Radical-Initiated Homo- and Copolymerization of Methacrylates

The paper presents data on the effect of iron metal complexes (ferrocene and dimer cyclopentadienyldicarbonyl iron) on the homo- and copolymerization of methyl methacrylate and butyl methacrylate initiated by benzoyl peroxide. It was shown that, in the presence of the metal complexes, the shapes of kinetic curves changed, and the compositions of copolymers and the initial mixtures of monomers almost coincided; that is, the resulting copolymer composition corresponded to the azeotropic composition. The copolymerization constants were close to unity. The presence of metallocenes affected the microstructure of the copolymers and their molecular-weight characteristics. These changes were explained by the formation of macromolecules with the participation of both free radicals and coordination active centers formed in the presence of the metal complexes.

Synthesis and mechanistic investigation of iron(II) complexes of isoniazid and derivatives as a redox-mediated activation strategy for anti-tuberculosis therapy

The emergence of multidrug-resistant strains of Mycobacterium tuberculosis (MTB) represents a major threat to global health. Isoniazid (INH) is a prodrug used in the first-line treatment of tuberculosis. It undergoes oxidation by a catalase-peroxidase KatG, leading to generation of an isonicotinoyl radical that reacts with NAD(H) forming the INH-NADH adduct as the active metabolite. A redox-mediated activation of isoniazid using an iron metal complex was previously proposed as a strategy to overcome isoniazid resistance due to KatG mutations. Here, we have prepared a series of iron metal complexes with isoniazid and analogues, containing alkyl substituents at the hydrazide moiety, and also with pyrazinamide derivatives. These complexes were activated by H2O2 and studied by ESR and LC-MS. For the first time, the formation of the oxidized INH-NAD adduct from the pentacyano(isoniazid)ferrate(II) complex was detected by LC-MS, supporting a redox-mediated activation, for which a mechanistic proposition is reported. ESR data showed all alkylated hydrazides, in contrast to non-substituted hydrazides, only generated alkyl-based radicals. The structural modifications did not improve minimal inhibitory concentration (MIC) against MTB in comparison to isoniazid iron complex, providing support to isonicotinoyl radical formation as a requirement for activity. Nonetheless, the pyrazinoic acid hydrazide iron complex showed redox-mediated activation using H2O2 with generation of a pyrazinoyl radical intermediate and production of pyrazinoic acid, which is in fact the active metabolite of pyrazinamide prodrug. Thereby, this strategy can also unveil new opportunities for activation of this type of drug.

Iron‐Promoted Radical Reactions: Current Status and Perspectives

AbstractCatalysis based on precious metals has reached an incredible level of sophistication and has found widespread use and application, both in academia and in industry. However, owing to the environmental impact, cost, and low abundance, catalysis based on inexpensive, abundant, and environmentally benign first‐row transition metals has become a valuable alternative to traditional reactions promoted by their less‐abundant counterparts. From economic and ecological perspectives, iron salts and iron metal complexes are highly promising candidates to replace costly and toxic metals. In recent years, iron complexes have been used to promote the formation of radicals. Photoredox chemistry is a valuable method for the generation of radical species under mild conditions, but it often relies on rare‐earth‐metal complexes. The employment of iron complexes for the generation of radicals is attractive for the development of sustainable, simple, and effective procedures. In this Focus Review, we highlight and summarize recent radical reactions promoted by iron complexes and their application in organic reactions.

Dehydrogenative silylation of alcohols catalysed by half-sandwich iron N-heterocyclic carbene complexes

A new series of tetramethylcyclopentadienyl-functionalised N-heterocyclic carbene complexes of iron bearing different wingtips of general type (Cp*-NHCR)Fe(CO)I (R = nBu, iBu, Et, CH2CH2OMe, CH2Ph) were prepared by direct reaction of Fe3(CO)12 and the corresponding imidazolium proligands. These new iron-NHC complexes have been found to be efficient catalysts for the dehydrogenative silylation of alcohols with silanes. Iron metal complexes bearing iso-butyl and n-butyl wingtips displayed slightly better catalytic performances than the related complexes (Cp*-NHCR)Fe(CO)I (R = Et, CH2CH2OMe, CH2Ph), affording quantitative yields of the corresponding silylethers in 8 h at 70 °C in acetonitrile.

Peroxidative oxidation of cyclic and linear hexane catalysed by supported iron complexes under mild and sustainable conditions

The development of economical heterogeneous catalysts based on first row transition metal complexes that work under mild and sustainable reaction conditions in the activation of CH bonds is very important. Herein, commercially available iron(II) and iron(III) acetylacetonate were immobilised onto amine functionalised economical and environmentally acceptable solid porous supports: hexagonal mesoporous silica and activated carbon. The materials prepared by this very simple and straightforward methodology were characterised by elemental analysis, ICP-AES, FTIR, isotherms of adsorption at 77K and thermogravimetry. It showed that both porous materials were conveniently functionalised with amine groups and that the iron metal complexes could be effectively anchored onto these materials. The immobilised iron salts were active as heterogeneous catalysts in the oxidation of cyclohexane and n-hexane at room temperature with hydrogen peroxide, giving the respective alcohols and ketones. They could also be recycled at least two times without loss of catalytic activity in the oxidation of cyclohexane. In the oxidation of n-hexane this was only true for the anchored Fe(II) salts. In the oxidation of cyclohexane, both iron salts are more active heterogeneous catalysts anchored onto the activated carbons than onto the hexagonal mesoporous silicas. The opposite is observed in the oxidation of n-hexane. The heterogeneous catalysts reported herein are economical and work under mild reaction conditions and thus could be valuable for the improvement of the sustainability and environmental impact of processes currently used in industry.

PH-Dependent reactivity of oxidants formed by iron and copper-catalyzed decomposition of hydrogen peroxide

The decomposition of hydrogen peroxide catalyzed by iron and copper leads to the generation of reactive oxidants capable of oxidizing various organic compounds. However, the specific nature of the reactive oxidants is still unclear, with evidence suggesting the production of hydroxyl radical or high-valent metal species. To identify the reactive species in the Fenton system, the oxidation of a series of different compounds (phenol, benzoic acid, methanol, Reactive Black 5 and arsenite) was studied for iron- and copper-catalyzed reactions at varying pH values. At lower pH values, more reactive oxidants appear to be formed in both iron and copper-catalyzed systems. The aromatic compounds, phenol and benzoic acid, were not oxidized under neutral or alkaline pH conditions, whereas methanol, Reactive Black 5, and arsenite were oxidized to a different degree, depending on the catalytic system. The oxidants responsible for the oxidation of compounds at neutral and alkaline pH values are likely to be high-valent metal complexes of iron and copper (i.e., ferryl and cupryl ions).

Nonlinear absorption reversing between an electroactive ligand and its metal complexes

We present the nonlinear absorption investigation of an electroactive ligand and two ruthenium and iron metal complexes under 532 nm, 30 ps laser excitation, by the "open aperture" Z-scan technique. Significant nonlinear optical parameters have in all cases been measured, while the nonlinear attribute has been found to change from saturable to reverse saturable absorption between the initial ligand and its complexes.

Transition metal complexes of a super rigid anthyridine ligand: structural, magnetic and DFT studies

Transition metal complexes of iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) with a plane, super rigid ligand, 1,13,14-triaza-dibenz[a,j]anthracene (L), [M2L4](ClO4)4 (M = Fe, Co, Ni, Cu, Zn), were synthesized and their magnetic properties were studied. All complexes are dinuclear, tetracationic complexes bridged by four tridentate ligands. In a complex each L coordinates to two metal atoms with two nitrogen atoms chelating to one metal and the third nitrogen atom mono-coordinating to another metal. Crystal structure analysis indicated that the molecular structures of the five complexes are essentially the same despite significant distortion from the Jahn–Teller effect of the copper complex. The Cu–Cu distance is 2.907(1) A, and all other M–M distances are ca. 3.3 A. Antiferromagnetic couplings were observed for the Fe, Co, Ni and Cu complexes. The exchange parameters were J = −6 and −129 cm−1 for Ni and Cu complexes, respectively. The mechanism was discussed by spin-polarization, superexchange coupling and DFT calculations. The J value obtained from the density functional B3LYP calculations is in good agreement with the experimentally determined value.

Zinc-rich compounds of iron and cobalt: Formation of [Fe2Znn] (n = 2–4) and [Co2Zn3] cores

The reactions of heteroleptic GaCp*/CO containing transition metal complexes of iron and cobalt, namely [(CO)(3)M(μ(2)-GaCp*)(m)M(CO)(3)] (Cp* = pentamethylcyclopentadienyl; M = Fe, m = 3; M = Co, m = 2) and [Fe(CO)(4)(GaCp*)], with ZnMe(2) in toluene and the presence of a coordinating co-solvent were investigated. The reaction of the iron complex [Fe(CO)(4)(GaCp*)] with ZnMe(2) in presence of tetrahydrofurane (thf) leads to the dimeric compound [(CO)(4)Fe{μ(2)-Zn(thf)(2)}(2)Fe(CO)(4)] (1). Reaction of [(CO)(3)Fe(μ(2)-GaCp*(3))Fe(CO)(3)] with ZnMe(2) and stoichiometric amounts of thf leads to the formation of [(CO)(3)Fe{μ(2)-Zn(thf)(2)}(2)(μ(2)-ZnMe)(2)Fe(CO)(3)] (2) containing {Zn(thf)(2)} as well as ZnMe ligands. Using pyridine (py) instead of thf leads to [(CO)(3)Fe{μ(2)-Zn(py)(2)}(3)Fe(CO)(3)] (3) via replacement of all GaCp* ligands by three{Zn(py)(2)} groups. In contrast, reaction of [(CO)(3)Co(μ(2)-GaCp*)(2)Co(CO)(3)] with ZnMe(2) in the presence of py or thf leads in both cases to the formation of [(CO)(3)Co{μ(2)-ZnL(2)}(μ(2)-ZnCp*)(2)Co(CO)(3)] (L = py (4), thf (5)) via replacement of GaCp* with {Zn(L)(2)} units as well as Cp* transfer from the gallium to the zinc centre. All compounds were characterised by NMR spectroscopy, IR spectroscopy, single crystal X-ray diffraction and elemental analysis.

ChemInform Abstract: Highlights of Current Research Involving Superoxide and Perhydroxyl Radicals in Aqueous Solutions

SummarySelected topics of current research on HO2/O−2 radical reactions in aqueous solutions are described. The subject is introduced by a brief review of the fundamental background chemistry of HO2/O−2, including a description of the rates and mechanisms of formation and decay as well as their spectral properties, current research on self-exchange rates, etc. This is followed by examples of their reactivity with simple metal complexes of iron, manganese and copper and extended to some biological significant metal-containing systems such as porphyrins, haem enzymes and superoxide dismutases. Some recent results on the interaction of these oxy-radicals with antioxidants, specifically vitamin C and E, are discussed. A brief review of some topical chemistry describing HO2/O−2 involvement in atmospheric and aquatic chemistry is given. Finally, some new trends in the areas of heterogeneous catalysis and reactor chemistry that involve these species are described.