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In this work, synthesis, characterization, and antioxidant activities of two Schiff base monomers (1 and 2) and their corresponding oxidation products (3 and 4) were reported. The monomers were prepared by condensation of 8-amino-2-naphthol with 2,4-dihydroxybenzaldehyde and 3,4-dihydroxybenzaldehyde, and then, they were oxidized to in alkaline medium by NaOCl to obtain the corresponding oxidation products. The compounds 1-4 were characterized by various spectral techniques. The analysis results indicated that the oxidation products had a chain structure consisting of randomly ordered phenylene and oxyphenylene units. In vitro antioxidant activities of 1-4 were evaluated against a ABTS cation radical and a DPPH free radical and compared with standard natural antioxidants, vitamin C (ascorbic acid), and vitamin E ([alpha]-tocopherol). The ferric reducing antioxidant power and ferrous-ion chelating activities of 1-4 were also determined. Key words: oxidative polymerization, Schiff base, phenol, antioxidant activity. Dans le cadre des presents travaux, nous decrivons la synthese, la caracterisation et l'activite antioxydante de deux bases de Schiff employees comme monomeres (1 et 2) et de leurs produits d'oxydation respectifs (3 et 4). Nous avons prepare les monomeres par condensation du 8-amino-2-naphtol avec le 2,4-dihydroxybenzaldehyde et le 3,4-dihydroxybenzaldehye, puis nous les avons soumis a une oxydation par le NaOCl en milieu alcalin pour obtenir les produits d'oxydation correspondants. Nous avons caracterise les composes 1 a 4 a l'aide de diverses techniques spectrales. Les resultats de l'analyse indiquent que les produits d'oxydation presentent une structure en chaine composee d'unites de phenylene et d'oxyphenylene ordonnees de maniere aleatoire. Nous avons evalue l'activite antioxydante in vitro des composes 1 a 4 a l'egard du radical cationique ABTS et du radical libre DPPH, et nous l'avons comparee a celle d'antioxydants naturels, a savoir la vitamine C (acide ascorbique) et la vitamine E ([alpha]-tocopherol). Nous avons egalement soumis les composes 1 a 4 au test de capacite de reduction des ions ferriques et au test de capacite chelatrice des ions ferreux. [Traduit par la Redaction] Mots-cles : polymerisation oxydante, base de Schiff, phenol, activite antioxydante., Introduction The polymers we use in our daily life are often exposed to various oxidative stresses. This leads to deterioration in their physical and mechanical properties and shortens their shelf [...]

Abstract: Soft X-ray-induced radiation chemistry in selected Fe molecular compounds and some aliphatic polymers was studied using soft X-ray absorption spectroscopy, and scanning transmission X-ray microscopy. X-ray absorption near-edge structure [...]

Abstract: The effects of solvation on iron salts has been studied by in situ X-ray absorption spectroscopy (XAS). It was seen that the solvated iron is significantly different from the [...]

Abstract: The adsorption of ferroin by graphite oxide was studied by changing different parameters, i.e., pH, duration, concentration of ferroin, adsorbent dose, and temperature. The removal of ferroin in aqueous [...]

An important parameter of the quality of petroleum products is the concentration of metals, including aluminum and iron, that can be present in petroleum products as various inorganic and organic [...], A procedure is developed for the cyclic-injection spectrophotometric determination of iron and aluminum in petroleum products; it includes microwave sample mineralization followed by the determination of analyses as their complexes with Chrome Azurol S at pH 5. The classical least-squares technique is used for the simultaneous determination of iron and aluminum. The analytical range for elements covers from 10 to 100 mg/kg at a sample weight of 1 g. The limits of detection for both elements are 3 mg/kg. The developed procedure was used for the determination of iron and aluminum in the spent engine oil and marine fuel. Keywords: cyclic-injection analysis, spectrophotometry, chemometrics, classical least-squares technique, petroleum products, iron, aluminum, Chrome Azurol S DOI: 10.1134/S1061934814120132

Captopril, 1-[(2s)-3-mercapto-2-methylpropionyl]-L-proline (Scheme 1), is an orally active inhibitor of the angiotensin converting enzyme and is widely used for the treatment of hypertensive disease on its own or in combination [...], A modified carbon paste electrode was prepared by incorporating multi-wall carbon nanotubes with a ferrocene-based polyamide (FDADO-IPC). A mixture of fine graphite powder with 10 wt % of multi-wall carbon nanotubes was applied to the preparation of the carbon paste (by dispersing in paraffin) that was finally modified with a ferrocene polyamide complex. The electrocatalytic oxidation of captopril (CAP) was investigated on the surface of the FDADO-IPC multi-wall carbon nanotubes modified carbon paste electrode (FDADO-IPC-MCNTPE) using cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry (CHA) and chronocoloumetry (CHC). Using the modified electrode, the kinetics of CAP electrooxidation was considerably enhanced by lowering the anodic overpotential through a catalytic fashion. A linear dynamic range of 0.2-200 µM for CAP was obtained in buffered solutions at pH 7.0. The detection limit was 0.08 µM. Differential pulse voltammetry as a simple, rapid, sensitive, and selective method was developed for the determination of CAP in tablet and human urine without any treatment. Keywords: captopril, ferrocene-based polyamide, carbon nanotubes paste electrode, electrocatalysis DOI: 10.1134/S106193481402004X

The interaction among topological defects can induce novel phenomena such as disclination pairs in liquid crystals and super-conducting vortex lattices. Nanoscale topological vortices with swirling ferroelectric, magnetic, and structural antiphase relationships were found in multiferroic h-YMn[O.sub.3]. Herein, we report the discovery of intriguing, but seemingly irregular configurations of a zoo of topological vortices and antivortices. These configurations can be neatly analyzed in terms of graph theory and reflect the nature of self-organized criticality in complexity phenomena. External stimuli such as chemistry-driven or electric poling can induce the condensation and eventual annihilation of topological vortex--antivortex pairs. doi/ 10.1073/pnas.1011380107

[Fe.sup.III]-[O.sub.2.sup.*-] intermediates are well known in heme enzymes, but none have been characterized in the nonheme mononuclear [Fe.sup.II] enzyme family. Many steps in the [O.sub.2] activation and reaction cycle of [Fe.sup.II]-containing homoprotocatechuate 2,3-dioxygenase are made detectable by using the alternative substrate 4-nitrocatechol (4NC) and mutation of the active site His200 to Asn (H200N). Here, the first intermediate (Int-1) observed after adding [O.sub.2] to the H200N-4NC complex is trapped and characterized using EPR and Mossbauer (MB) spectroscopies. Int-1 is a high-spin ([S.sub.1] = 5/2) [Fe.sup.III] antiferromagnetically (AF) coupled to an [S.sub.2] = 1/2 radical (J [approximately equal to] 6 [cm.sup.-1] in H = [JS.sub.1]*[S.sub.2]). It exhibits parallel-mode EPR signals at g = 8.17 from the S = 2 multiplet, and g = 8.8 and 11.6 from the S = 3 multiplet. These signals are broadened significantly by [sup.17][O.sub.2] hyperfine interactions ([A17.sub.O] [approximately equal to] 180 MHz). Thus, Int-1 is an AF-coupled [Fe.sup.III]-[O.sub.2.sup.*-] species. The experimental observations are supported by density functional theory calculations that show nearly complete transfer of spin density to the bound [O.sub.2]. Int-1 decays to form a second intermediate (Int-2). MB spectra show that it is also an AF-coupled [Fe.sup.III]-radical complex. Int-2 exhibits an EPR signal at g = 8.05 arising from an S = 2 state. The signal is only slightly broadened by [sup.17][O.sub.2] ( oxygen activation | oxygenase | spectroscopy | superoxide doi/ 10.1073/pnas.1010015107

The hetero-Diels--Alder reactions of butadiene with Fe[(CO).sub.3]-coordinated formylbutadiene and formyltrimethylenemethane catalyzed by Lewis acids have been theoretically studied through density functional calculations. The results obtained show that, for the reaction with (formylbutadiene)Fe[(CO).sub.3], the kinetically most favourable product is the one corresponding to the attack of butadiene on the s-cis conformer of the formylbutadiene fragment when the reaction is catalyzed by [BF.sub.3], and the one corresponding to the attack on the s-trans conformer when the catalyst is Ti[Cl.sub.4]. On the other hand, for the reaction with (formyltrimethylenemethane) Fe[(CO).sub.3] catalyzed by [BF.sub.3], the product corresponding to the attack on the s-trans conformer is predicted to be favoured. These results have been interpreted through an energy decomposition analysis of the potential-energy barriers. Key words: Fe[(CO).sub.3] complexes, hetero-Diels--Alder reactions, density functional theory, Lewis acid catalysis. Faisant appel a la methode de calcul de la fonctionnelle de la densite, on a etudie d'une facon theorique les reactions d'hetero-Diels--Alder catalysees par des acides de Lewis du butadiene avec du formylbutadiene et du formyltrimethyle nemethane coordines au Fe[(CO).sub.3]. Les resultats obtenus montrent que, pour la reaction avec le (formylbutadiene) Fe[(CO).sub.3] catalysee par le [BF.sub.3], le produit le plus favorable d'un point de vue cinetique correspond a celui obtenu par une attaque du butadiene sur le conformere s-cis du fragment formylbutadiene alors que pour la reaction catalysee par le Ti[Cl.sub.4] le produit le plus favorable correspond a une attaque sur le conformere s-trans. Par ailleurs, pour la reaction avec le (formyltrimethyle nemethane) Fe[(CO).sub.3], catalysee par le [BF.sub.3], les calculs predisent que le produit favorise serait celui correspondant a une attaque sur le conformere s-trans. On interprete ces resultats par le biais d'une analyse par decomposition de l'energie des barrieres a l'energie potentielle. Mots-cles : complexes Fe[(CO).sub.3], reactions hetero-Diels--Alder, theorie de la fonctionnelle de la densite, catalyse par un acide de Lewis. [Traduit par la Redaction], Introduction Diene tricarbonyl iron complexes are very valuable tools in organic synthesis. (2-12) The iron tricarbonyl unit is a very efficient protecting group for 1,3-diene and facilitates an excellent chirality [...]

The reduction kinetics of two explosives, 2,4,6-trinitrotoluene (TNT) and hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX), by Fe(II) was investigated in aqueous systems. A dilute ferrous iron solution effectively reduces these nitroaromatic (NAC) and nitramine (NAM) compounds between pH 6.75 and 9.2. Observed reaction rates are first order in monohydroxl and dihydroxyl ferrous iron [FeO[H.sup.+] or Fe[(OH).sup.0.sub.2]], and NAC/NAM concentrations. The reaction does not require the presence of a mediating surface. Intrinsic rate constants for TNT and RDX reduction by monohydroxyl ferrous iron are 2.00([+ or -] 0.17)E + 09 and 2.04([+ or -] 0.24)E + 06 [M.sup.- 2] [s.sup.-1], respectively. The reduction half-lives at neutral pH were on the order of minutes for TNT and hours for RDX, yielding rates faster than any known natural process or current bioremediation technique. The use of a mobile reductant, such as hydroxyl-complexed Fe(II) or other aqueous Fe(II) complexes, for NAC/NAMs could be an effective remediation technique at contaminated sites. DOI: 10.1061/(ASCE)0733-9372(2008)134:12(937) CE Database subject headings: Kinetics; Groundwater pollution; Organic matter; Toxicity; Remedial action.

Thermochemical cycles are a type of heat engine that utilize high-temperature heat to produce chemical work. Like their mechanical work producing counterparts, their efficiency depends on the operating temperature and on the irreversibility of their internal processes. With this in mind, we have invented innovative design concepts for two-step solar-driven thermochemical heat engines based on iron oxide and iron oxide mixed with other metal oxide (ferrites) working materials. The design concepts utilize two sets of moving beds of ferrite reactant materials in close proximity and moving in opposite directions to overcome a major impediment to achieving high efficiency--thermal recuperation between solids in efficient countercurrent arrangements. They also provide an inherent separation of the product hydrogen and oxygen and are an excellent match with a high-concentration solar flux. However, they also impose unique requirements on the ferrite reactants and materials of construction as well as an understanding of the chemical and cycle thermodynamics. In this paper, the counter-rotating-ring receiver/reactor/ recuperator solar thermochemical heat engine concept is introduced, and its basic operating principles are described. Preliminary thermal efficiency estimates are presented and discussed. Our results and development approach are also outlined. Keywords: solar, thermochemical, hydrogen, metal oxide, ferrite, redox, heat engine

The studies have shown that in both native and reconstituted [4Fe-4S] FNR, the reaction environment and the presence of [Fe.sup.2} and [Fe.sup.3} chelators have influenced the cluster conversion reactions. The sensitivity of FNR cluster conversion kinetics to chelators has disclosed mechanism by which the cell can fine-tune its response to the onset of aerobic conditions.

The effects of 10 paramagnetic metal complexes on [F.sup.-] ion [super 19]F NMR transverse relaxation rates are studied in aqueous solutions as a function of temperature. The results have shown that [F.sup.-] [super 19]F NMR relaxation is used for predicting the reactivities of other [Fe.sup.III] complexes toward reduction by [O.sub.2.sup.-], which is a key step in the biological production of reactive oxygen species.

Author(s): Justin F. Acheson [1]; Lucas J. Bailey [1]; Thomas C. Brunold [2]; Brian G. Fox (corresponding author) [1] Aromatic rings are among the most widely distributed and recognizable forms [...], Electrophilic aromatic substitution is one of the most important and recognizable classes of organic chemical transformation. Enzymes create the strong electrophiles that are needed for these highly energetic reactions by using O[sub.2], electrons, and metals or other cofactors. Although the nature of the oxidants that carry out electrophilic aromatic substitution has been deduced from many approaches, it has been difficult to determine their structures. Here we show the structure of a diiron hydroxylase intermediate formed during a reaction with toluene. Density functional theory geometry optimizations of an active site model reveal that the intermediate is an arylperoxo Fe[sup.2+]/Fe[sup.3+] species with delocalized aryl radical character. The structure suggests that a carboxylate ligand of the diiron centre may trigger homolytic cleavage of the OO bond by transferring a proton from a metal-bound water. Our work provides the spatial and electronic constraints needed to propose a comprehensive mechanism for diiron enzyme arene hydroxylation that accounts for many prior experimental results.

The iron(III) complexes of 1,4,8,11-tetraaza[14]annulenes are prepared as catalase mimics. A non-oxygen releasing pathway of hydrogen peroxide decomposition is disclosed besides oxygen production.

The crystal structure, thermal studies and magnetic properties of [Fe[(bpp).sub.2]][[Cr(L)[(ox).sub.2]].sub.2].n[H.sub.2]O complexes are described. The effect of lattice solvent in the magnetic properties of these spin-crossover complexes is examined by a combined structural, calorimetric and magnetic study.

Ab initio calculations are used for studying the origin of the spin-transition behavior of the Prussian blue analogue cesium iron hexacyanochromate CsFe[Cr[(CN).sub.6]]. The studies have shown that the spin-transition phenomenon in the Prussian blue analogue CsFe[Cr[(CN).sub.6]] compound is driven by charge reorganization within the matrix.

The rates of proton transfer to synthetic Fe-S-based clusters with a binuclear core composition [{MeFe[S.sub.2]}.sup.n} (M = Fe, Mo or W) containing [[mu].sub.2]-S are analyzed. The results have helped in examining the affects of metal composition, terminal ligands and nuclearity on the rates of proton transfer.

The uncatalyzed reactions of [O.sub.2] (S = 1) with organic substrates (S = 0) are thermodynamically favorable but kinetically slow because they are spin-forbidden and the one-electron reduction potential of [O.sub.2] is unfavorable. In nature, many of these important [O.sub.2] reactions are catalyzed by metalloenzymes. In the case of mononuclear non-heme iron enzymes, either [Fe.sup.II] or [Fe.sup.III] can play the catalytic role in these spin-forbidden reactions. Whereas the ferrous enzymes activate [O.sub.2] directly for reaction, the ferric enzymes activate the substrate for [O.sub.2] attack. The enzyme-substrate complex of the ferric intradiol dioxygenases exhibits a low-energy catecholate to [Fe.sub.III] charge transfer transition that provides a mechanism by which both the Fe center and the catecholic substrate are activated for the reaction with [O.sub.2]. In this Perspective, we evaluate how the coupling between this experimentally observed charge transfer and the change in geometry and ligand field of the oxidized metal center along the reaction coordinate can overcome the spin-forbidden nature of the [O.sub.2] reaction.

The synthesis of a family of iron(II) spin crossover monomers containing the bis-meridional ligands 2-(1-pyridin-2-ylmethyl-1H-pyrazol-3-yl)-pyrazine (picpzpz) and 2-(3-(2-pyridyl)pyrazol-1-ylmethyl)pyridine) (picpypz) is described.

We report evidence for high ferric iron to total iron ([Fe.sup.3+]/[SIGMA]Fe) ratios in Al-bearing akimotoite coexisting with other high-pressure silicates and Fe-Ni metal from shock melt-veins in the Sixiangkou (L-6) chondrite. The measurements were made using electron energy-loss near-edge structure (ELNES) spectroscopy. The results demonstrate that akimotoite in shock-melt veins of this meteorite has high proportions of [Fe.sup.3+], with a [Fe.sup.3+]/[SIGMA]Fe ratio of 0.67(3). In contrast, the coexisting majoritic garnet and ringwoodite, which are the typical Fe-bearing phases in shock veins in this meteorite, are enriched in [Fe.sup.2+] rather than [Fe.sup.3+], with [Fe.sup.3+]/[SIGMA]Fe ratios of 0.10(5) and 0.15(5), respectively. We conclude that the higher affinity of [Fe.sup.3+] for akimotoite, rather than for the other dense silicate phases, is related strongly to the substitution mechanism of trivalent cations. This mechanism is described as [sup.VI(A)][Fe.sup.3+] + [sup.VI(B)][Al.sup.3+] = [sup.VI(A)][Mg.sup.2+] + [sup.VI(B)][Si.sup.4+] in the AB[O.sub.3] structural formula of MgSi[O.sub.3]-ilmenite under high pressures and temperatures, and operates even at a low oxygen fugacity where Fe-Ni metal is stable. Keywords: Meteorite, L-6 chondrite, electron microscopy, Fe-bearing silicates, akimotoite, high pressure, shock-melt vein

The mechanisms of highly selective ferric ion sorption, as well as the exchange by the crystalline metal phosphonates that are constructed from the tetraphosphonic acids are described. These materials exhibit excellent ferric ion uptake capacities due to the electrostatic attraction between them.

The fabrication of thin films of stabilized-[Fe.sub.3][O.sub.4] nanoparticles and a vast monolayer of [Fe.sub.3][O.sub.4] magnetic nanoparticles which was prepared by Langmuir-Blodgett are reported.

Experimental and theoretical methods are used for characterizing a series of Ir(III)-based heteroleptic complexes with phenylpyridine (ppy) and 2-(5-phenyl-4H-[1,2,4]-triazol-3-yl)pyridine (ptpy) derivatives as coordinating ligands. The results have shown that the extent of charge-transfer contributions have depended on the energy gaps between the relevant molecular orbitals, which can be modified by the substitution pattern.

Femtosecond fluorescence up-conversion and transient absorption (TA) studies are used for characterizing the ultrafast relaxation of aqueous iron(II)-tris(bipyridine) upon excitation into the singlet metal-to-ligand charge-transfer band (MLCT). A simple model of avoided crossings between singlet and triplet potential curves is proposed that is induced by the strong spin-orbit interaction.

A series of experiments are described that have elucidated the mechanism of N[double bond]N cleavage by an iron-hydride complex. It is shown that the high-spin iron(II) hydride can break N-N bonds through both nonradical and radical insertion mechanisms, which is a special feature that enables novel reactivity.

The synthesis and two-step spin crossover behavior of Fe[(bpp).sub.2]][Pt[(ox).sub.2]].[H.sub.2]O where bpp is 2,6-bis(pyrazol-3-yl)-pyridine and ox is oxalate, is described. The complex and unique transitional behavioral changes over many cycles are discussed.

The characterization and preparation of the first sphere mutant of soybean lipoxygenase-1, N694C which allows evaluation of the [sigma]-organoiron mechanism showing a significant deuterium isotope effect for kinetic data of N694C is presented.

A combination of studies is employed to analyze the thiolate bonding to [{FeNO}.sup.2]/[{[FeO.sub.2]}.sup.8] complexes of isopencillin N synthase (IPNS). The determination of oxidase substrate versus the oxygenase activity in nonheme Fe enzymes shows that the single center reaction in IPNS allows it to avoid the oxygen bridged binding completely.

The synthesis and reactivity of the EPR-active, anionic [{Fe[(NO).sub.2]}.sup.9], [[(S[C.sub.6][H.sub.4]-o-NCOPh)Fe[(NO).sub.2]].sup.-], [[[(S[C.sub.6][H.sub.4]-o-COO)Fe[(NO).sub.2]].sup.-], and [[[([N.sub.3]).sub.2]Fe[(NO).sub.2]].sup.-] containing a wide range of S/N/O ligation and the EPR-active, dimeric [{Fe[(NO).sub.2]}.sup.9]-[{Fe[(NO).sub.2]}.sup.9] DNICs [[Fe([mu]-S[C.sub.7][H.sub.4]SN)[(NO).sub.2]].sub.2] is presented.

The investigation of the thermal decomposition of iron(II) acetyl acetonate, Fe[([C.sub.5][H.sub.7][O.sub.2])].sub.2] in a closed cell at 700 degree Celsius conducted under a magnetic field of 10 T is reported.

The nonheme iron(IV)-oxo complexes give rise to oxygen during the oxidation and there is no removal of hydrogen atom as studied in the hydroxylation of aromatic compounds by these complexes.

The study presents a spectroscopic and computational analysis of the structure and properties of the high-spin Fe(IV)-oxo intermediates that are often used as the catalysts for the reactions of different proteins, including taurine. The methodology used here has probed to be extremely efficient and helpful, as it proves the existence of different residual structures in such intermediates, which include the [alpha]-ketoglutarate dioxygenase from Escherichia coli and its His99Ala ligand variant.

The X-ray structure of the blue complex, [Cu(L)(N[O.sub.3])][N[O.sub.3]] obtained from the reaction of Cu[(N[O.sub.3]).sub.2]*3[H.sub.2]O with the ligand 1-(ferrocenemethyl)-1,4,7,10-tetraazacyclododecane (L) in acetonitrile showed an unexpected binding of a nitrate anion in that C[u.sup.II] center. The nitrate anion in the C[u.sup.II] center is observed to be surrounded by four N atoms of the 1,4,7,10-tetraazacyclododecane (cyclen) macrocycle and two O atoms from chelating nitrate anion, both Cu-O distances being below the sums of the van de Waals radii.

Three pathways for the reaction of bispidine-iron(II) complexes are studied where bispidine is a rigid tetradentate amine/pyridine ligand with [H.sub.2][O.sub.2]. The findings reveal that there is a direct conversion of the dispidine-iron(II)-hydrogen peroxide complex to the corresponding iron(IV)-dihydroxo compound which is a novel possible oxidant for the dihyroxylation of olefins.

The electronic structure and bonding of the [{Fe(PhN[O.sub.2])}.sup.6] units were studied using model nitrobenzene complexes with cationic, neutral, and anionic forms of the ferrous center. The findings revealed that excess negative charge on the ferrous center, enhances the reduction of nitrobenzene, where as a positive charge effectively prevents this process.

A well-resolved vibronic fine structure is disclosed by the luminescence spectra of [[(tpy).sub.2]Ir[(CN-t-Bu).sub.2]](C[F.sub.3]S[O.sub.3]) in methylcyclohexane glass and frozen n-nonane at 15 K. The analysis has shown that the most highly distorted normal modes involve atomic motions on the tpy ligand, which is consistent with the metal to ligand/ligand centered assignment of the electronic transition.

The development of numerical modeling of reactive transport relies on the availability of thermodynamic properties for the solid, surface, aqueous, and vapor species stable at the conditions of interest. The lack of experimental studies and comprehensive activity-composition models severely limits the predictive capabilities of these models in systems involving highly saline fluids or low-density volatile-rich fluids. X-ray absorption near-edge structure spectroscopy (XANES) is a powerful technique to study the speciation of transition metals in aqueous fluids: it is element specific; sensitive to the oxidation state of the metal, the ligand field and the coordination geometry of the complex; and it is suitable for measuring trace amounts of metals ( Formation constants for the aqueous complexes of transition metals can be determined from a series of XANES spectra obtained on solutions containing a constant amount of the metal of interest and variable concentrations of a ligand. The method relies on a non-linear, least-squares-fitting approach, with full distribution of species calculations based on a complete thermodynamic model for the experimental system under consideration. The technique is particularly suitable for following octahedral to tetrahedral transitions among weak chloride complexes of transition metals. The log K for the reaction [Zn.sup.2+.sub.(octahedral)] + 4[Cl.sup.-] = Zn[Cl.sup.2-.sub.4 (tetrahedral)] at 25 [degrees]C is retrieved to be 0.1(6), within error of the accepted literature value. The same method applied to [Fe.sup.2+]-chloride complexes shows that the log K for the reaction [Fe.sup.2+.sub.(octahedral)] + 4[Cl.sup.-] = Fe[Cl.sup.2-.sub.4 (tetrahedral)] increases from -6.2(6) at 25 [degrees]C to -2.9(3) at 150 [degrees]C. This study confirms that tetrahedral chloride complexes play an important role in Fe transport in hypersaline brines especially at elevated temperatures, and shows that XANES is well suited to study systems that may be difficult to study with other techniques. Keywords: Fe and Zn chloride complexes, XAS, XANES, stability constants, thermodynamics, hydrothermal solutions

The synthesis of two cyclopropyl-containing tripeptide analogues designed as probes for the mechanism of isopenicillin N synthase is described. Findings reveal that key differences were found to exist in substrate orientation and water occupancy, which allow for an explanation of the differences in reactivity of these substrates.

The syntheses and reactivity of haloacetates of iron(II) are presented. The isolated compounds are formed due to C-X activation (X = Cl, Br) and haloacetato decomposition, which occurs with concomitant oxidation at the metal centers.

Two tricyanometallate precursors with low spin [Fe.sup.III] center are synthesized and characterized. The results have shown that the mononuclear compounds are the versatile building blocks for assembling new cyanide-bridged heterometallic high-spin clusters with interesting magnetic properties.

A two-dimensional (2D) iron(II) spin crossover (SC) complex, [[Fe.sup.II][(H[L.sup.H,Me]).sub.2][(Cl[O.sub.4]).sub.2].1.5MeCN, where (H[L.sup.H,Me] = imidazol-4-yl-methylidene-8-amino-2-methylquinoline), is synthesized. The effect of the solvent molecule and the coexistence of bifurcated hydrogen bonds and [pi]-[pi] interactions on SC behavior are examined.

A series of K, Fe, and Mn doped samples L[a.sub.1.95]K[0.05]M[o.sub.2-x][T.sub.x][O.sub.9-[delta]] (T=Fe, Mn; x=0,0.025,0.05,0.1) were prepared with conventional solid-state reaction method based on the oxygen ion conductor L[a.sub.2]M[o.sub.2][O.sub.9]. The findings reveal that the high-temperature conductivity of L[a.sub.2]M[o.sub.2][O.sub.9] could be improved by the Fe or Mn doping at Mo site and the low-temperature conductivity could be increased by the simultaneous K doping at La site.

The substitution reactions at the nickel site of the cubane type [[([Ph.sub.3]P)Ni[Fe.sub.3][S.sub.4](L[S.sub.3])].sup.2-] clusters relevant to the C-clusters of carbon monoxide dehydrogenase were investigated. It was found that [[([Ph.sub.3]P)Ni[Fe.sub.3][S.sub.4](L[S.sub.3])].sup.2-] supports substitution reactions with phosphine displacement by thiolate ligands to yield clusters with tetrahedral or planar stereochemistry at the nickel site.