Iron Cyanide Complexes Research Articles

Spectrophotometric determination of total cyanide, iron-cyanide complexes, free cyanide and thiocyanate in water by a continuous-flow system

A combination of three automated methods has been developed to determine total cyanide, free cyanide [i.e., HCN(aq)+ CN–], iron-cyanide complexes and thiocyanate. The methods are based on a continuous-flow technique, combined with spectrophotometric detection, and have a detection limit of 0.6 µg l–1. The distinction between iron-cyanide complexes and free cyanide plus thiocyanate was made by UV irradiation and distillation with citric acid. The distinction between free cyanide and thiocyanate was made by masking free cyanide with formaldehyde. Rapid and complete recovery of iron-cyanide complexes was obtained; the interference from nitrate was minimised. Shielding the samples from diffuse daylight appeared to be necessary to prevent rapid photolysis of the iron-cyanide complexes.

Determination of metal ion complexes in electroplating solutions using capillary zone electrophoresis with uv detection

Capillary zone electrophoresis with on-column UV detection at 214 nm was used to detect and determine iron cyanide complexes in liquid samples from zinc electroplating processes. Using a cathodic injection and anodic detection scheme, hexacyanoferrate(II) and -(III) ions were separated with separated with baseline resolution in under 5 min. A linear relationship between peak area and concentration was obtained for both ions, and the detection limit was lower than 10 μ M. The experiments were extended to detect the presence of zinc hydroxo complexes in plating solutions. The electrophoretic mobility of this species was determined from the migration times, sampling simultaneously the zinc species at the cathode and adenosine, a neutral molecule that migrates with the electroosmotic flow, at the anode. The results seem to indicate the rpesence of the doubly charged species Zn(OH) 2− 4 in Zn 11 solutions at pH > 10.5.

The effect of copper and iron complexation on removal of cyanide by ozone

not detected during ozonation of iron-cyanide complex. Complete destruction of free cyanide ion in aqueous solution has been reported unanimously by numerous re- searchers (Gurol and Bremen, 1985; Rowley and Otto, 1980; Zeelvalkink et al., 1979; Matsuda et al., 1975a,b; Balyanskii et al., 1972; Sondak and Dodge, 1961a,b; Khandelwal et al., 1959; Selm, 1959; Walker and Zabban, 1953). However, there is disagreement as to the effects of metal complexation

Simultaneous flow injection speciation of iron(II) and iron(III) cyano complexes utilizing electrochemical and atomic absorption detectors in series

A method is described for the simultaneous speciation of Fe(CN) 6 4− and Fe(CN) 6 3− in a flow injection (FIA) system comprising electrochemical (EC) and flame atomic absorption spectrometry (AAS) detectors in series. One of these species is detected amperometrically at a Pt-electrode by applying the required potential and measuring the resulting reduction or oxidation current of the appropriate iron cyanide complex. Total iron in both species is determined by an AAS detector. The EC detector is inherently more sensitive, with a detection limit of 0.5 Μg Fe l−1 and a relative standard deviation of 1.0% for a 0.040 Μg Fe ml−1 sample. The limit of detection for the AAS detector is 0.5 Μg Fe ml−1, and the relative standard deviation for a 5.70 Μg Fe ml−1 sample is 0.40%. The method enables up to 60 analyses (120 speciations) per hour and obviates the problem of easy oxidation of Fe(CN) 6 4− .

A photochargeable device composed of bilayer membranes of poly(3-methylthiophene) and prussian blue

A photochargeable device which can be charged under irradiation and discharged in the dark should open a new field of photoenergy conversion and storage. Such a device can be used also for information storage. Such a device can be used also for information storage. Some model cells for photoenergy conversion and storage have been constructed by using liquid-junction inorganic semiconductors in contact with a redox electrolyte solution [l-5]. Recently, organic semiconductors such as poly(acetylene) [6,7], poly(pyrrole) [&lo], poly(aniline) [ll], and poly(thienylene) [12,13] were reported to give photocurrents in the form of a Schottky type device. Although the light-to-electricity conversion efficiency of these organic semiconductor devices is inferior to that of inorganic semiconductor ones, they have merits in their easy fabrication, utilization as a film, and fairly high stability, except for poly(acetylene), in contrast to the corrosive narrow bandgap inorganic semiconductors. Prussian Blue (PB) is a polynuclear iron cyanide complex with the composition, Fe~‘[Fe”(CN),]~-. The electrochemical behavior of PB has been well characterized [14-161. Since PB is both oxidized and reduced reversibly, it can work as both the anode and cathode active material of a secondary battery [17-191. PB can be used as a fihn because of its high molecular weight structure. The photoelectrochemical reaction of a PB film coated on a TiO, liquid-junction photoanode was reported in ref. 20. In the present paper we will report the first example of an organic bilayer device composed of poly(3-methylthiophene) and PB which can be charged under irradiation and discharged in the dark reversibly.

The active site of aromatase cytochrome P-450. Differential effects of cyanide provide evidence for proximity of heme-iron and carbon-19 in the enzyme-substrate complex.

19-Norandrostenedione and androstenedione are shown to be metabolized by purified, reconstituted human placental aromatase cytochrome P-450. Kinetic evidence indicates that both steroids share a common catalytic site: 19-norandrostenedione is a competitive inhibitor of androstenedione aromatization, and the Ki value for its inhibition (120 nM) is similar to the Km value for its metabolism (132 nM). The two substrates differ, however, in their sensitivity to inhibition by the heme-iron ligand cyanide; 19-norandrostenedione is approximately 3-fold more sensitive to cyanide inhibition. Spectroscopic studies show that this differential inhibition by cyanide occurs because androstenedione competes with cyanide, whereas 19-norandrostenedione promotes cyanide binding to the heme-iron. It is proposed that these opposite effects on cyanide-iron coordination are due to the proximity of the heme-iron and C-19 of androstenedione in the enzyme-substrate complex, which results in steric exclusion of cyanide from the active site by the C-19 methyl group of androstenedione. Dioxygen is not excluded from binding to the heme-iron during catalysis, presumably because it bonds at an angle, in contrast to the linear bond of iron-cyanide complexes. A model for the active site of aromatase cytochrome P-450 is presented.

ChemInform Abstract: Mößbauer Spectroscopic Studies on Protoporphyrin IX Iron(III) Cyanide Complexes.

Chemischer InformationsdienstVolume 17, Issue 43 Physical Organic Chemistry ChemInform Abstract: Mößbauer Spectroscopic Studies on Protoporphyrin IX Iron(III) Cyanide Complexes. B. LUKAS, B. LUKASSearch for more papers by this authorJ. SILVER, J. SILVERSearch for more papers by this author B. LUKAS, B. LUKASSearch for more papers by this authorJ. SILVER, J. SILVERSearch for more papers by this author First published: October 28, 1986 https://doi.org/10.1002/chin.198643045Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume17, Issue43October 28, 1986 RelatedInformation

Chemical evolution of iron containing enzymes: mixed ligand complexes of iron as intermediary steps.

Activities of the iron complexes of evolutionary importance like K4[Fe(CN)6], K4[Fe(CN)5(gly)], and K4[Fe(CN)5(trigly)] have been tested towards some redox reactions of biological significance, namely, decomposition of hydrogen peroxide, dehydrogenation of NADH and ascorbic acid both coupled with reduction of methylene blue. It has been observed that the catalytic activities of iron (II) complexes towards the redox reactions studied at pH 9.18 followed the order, K4[Fe(CN)6] less than K4[Fe(CN)5(gly)] less than K4[Fe(CN)5(trigly)]. Decomposition of H2O2 catalysed by cyanocomplexes of iron (II) has been discussed through the formation of an innersphere complex in which loosly bound ligands like, glycine and triglycine are replaced by hydroperoxide ion. A tentative mechanism for the catalysed decomposition of H2O2 has been discussed. Based upon the experimental observations a hypothesis on the evolution of iron containing enzymes has been envisaged as: iron(II) ion----iron(II) cyanide complexes----mixed ligand iron(II) cyanide and amino acid complexes----iron(II) complexes of macromolecules----pŕoenzyme or early enzyme containing iron(II).

Characteristics of zeolite-supported iron catalysts prepared from iron cyanide complexes

This chapter discusses the catalytic properties of metal clusters in zeolites. Zeolites and molecular sieves offer a particularly intriguing option for providing channels and cage structures, in which small clusters might be formed and stabilized. The unusual properties of small particles might then be exploited, and the zeolitic structure may itself be utilized to fine-tune the catalytic properties. Several characterization techniques have been used in the examination of clusters in zeolites. The most widely used and/or useful appear to be extended X-ray absorption fine structure (EXAFS), the radial electron distribution (RED) method using X-ray scattering data (XRD), magnetic methods, electron microscopy, electron spin resonance (ESR), nuclear magnetic resonance (NMR) of adsorbed xenon, Mössbauer spectroscopy, X-ray photoelectron spectroscopy (XPS), chemisorption, including the use of temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO) and related methods and infrared (IR) spectroscopy. The chapter reveals that n-Butane conversion has been used as a test reaction for determining the catalytic properties of metal particles in zeolites and the parameters influencing these properties. Platinum has received the most attention and in these studies parameters such as particle size, support acidity, addition of other, metals, and sulphur poisoning are examined.

An electrochemical study of depression of flotation of chalcocite by cyanide and iron-cyanide complexes

The depression of chalcocite flotation with cyanide, ferrocyanide and ferricyanide was investigated through measurements of the potential of chalcocite electrodes (E) and the redox potential of the solution (Eh). Cyanide was found to be the strongest depressant, and its action is time dependent. The potential of chalcocite changed markedly in the presence of cyanide, decreasing rapidly to negative values, and this was associated with the depression of flotation. After a certain time the E is recovered along with the flotation. In this system flotation of chalcocite is only possible at E values >−40 mV. Evidence supporting the chemical dissolution of the collector coating and the decomposition of dixanthogen by cyanide are reported.

An electrochemical study of depression of flotation of chalcocite by cyanide and iron-cyanide complexes

The depression of chalcocite flotation with cyanide, ferrocyanide and ferricyanide was investigated through measurements of the potential of chalcocite electrodes (E) and the redox potential of the solution (Eh). Cyanide was found to be the strongest depressant, and its action is time dependent. The potential of chalcocite changed markedly in the presence of cyanide, decreasing rapidly to negative values, and this was associated with the depression of flotation. After a certain time the E is recovered along with the flotation. In this system flotation of chalcocite is only possible at E values >−40 mV. Evidence supporting the chemical dissolution of the collector coating and the decomposition of dixanthogen by cyanide are reported.

The reaction of nitrogen dioxide with iron(III) cyanide complexes

The kinetics of reaction of [Fe III 2(CN) 10] 4− with nitric and nitrous acids has been shown to fit the following rate law: rate = k h 1 2 [HNO 2] 1 2 [nitrate] 1 2 [Fe III 2(CN) 2− 10] The primary product appears to be a binuclear Fe III, Fe II cyanide complexes with an NO + ligand in the coordination shell of the ferrous ion. The kinetics of reaction and the properties of the product show a close resemblance to those of the reaction [Fe III(CN) 6] 3− with nitric and nitrous acids follow a similar rate law, though the dependence of rate upon acidity and nitrate concentration has not been determined. Rate = k[HNO 2] 1 2 [complex] It is concluded that the reaction of iron(III) cyanide complexes with nitric and nitrous acids to form iron(II) cyano nitrosyl products occurs through NO • 2 as the active nitrogen species.

Radiation-induced oxidation and reduction of iron–cyanide complexes

The species [Fe(CN)6]3− was generated by ionizing radiation in single crystals of Na4Fe(CN)6⋅10H2O maintained at 4.2°K. Three different conformations of the complex were obtained giving g tensors whose principal values are the following: 2.68, 2.53, 1.19; 2.74, 2.43, 0.63, and 2.81, 2.28, 1.45. Reduction products are formed in which the unpaired electron occupies an antibonding molecular orbital formed from iron and ligand orbitals.

Structure of cyanide methemoglobin

X-ray difference Fourier analysis at 2.8 Å resolution shows that the tertiary structures of horse cyanide methemoglobin and methemoglobin differ significantly. The conformations of the heme groups and their interactions with the globin are altered. Short contacts with globin side chains affect cyanide binding to the hemes, and the changes in globin-ligand contact upon substitution of cyanide for water in turn directly affect globin structure. Although the ligand peaks lie off the heme axes, the atoms FeCN may still lie on a straight line (as they do in small iron cyanide complexes), with this line not normal to the mean heme plane. This linear binding configuration is consistent with the observed motion and deformation of the porphyrin. Although motion of the iron atoms is not directly apparent, there is evidence that some changes in tertiary structure are induced by shortening of the iron-pyrrol nitrogen bond lengths. This and other studies suggest that the structural changes responsible for co-operativity in hemoglobin may be initiated not merely by an alteration in the covalent porphyrin-proximal histidine linkage, but by changes in the noncovalent interactions of the globin with the ligand and porphyrin as well.

Investigation of oxidation ? Reduction reactions in iron cyanide complexes by the method of gamma resonance spectroscopy

1. Isotopic and electron exchange was studied in the systems Fem+[Fe(CN)6]n−. 2. The parameters of the spectra of iron within and outside the sphere, entering into ferri-ferro-cyanides, were refined by a combination of gamma resonance spectroscopy and the labeled atom method, 3. In the system Fe2+−[FeIII(CN)6]3−, at a reagent ratio of 1∶1, there is a rapid oxidation-reduction process with transfer of an electron from iron within the sphere to iron outside the sphere. 4. In the presence of excess high-spin iron, at first the starting materials react in a 1:1 ratio, forming the soluble blue KFe3+[Fe(CN)6], and only then is there a slow replacement of potassium cations of the iron — cyanide complex by Fe3+ ions. If in this case the blue is produced from an excess of Fe3+ and the ferrocyanide ion [Fe(CN)6]4−, then at the second stage the initial high-spin ferri-eations enter into the reaction. If, however, the starting materials were Fe2+ ions (in excess) and the ferricyanide anion [FeIII ·(CN)6]3−, then first the stoichiometric amount of Fe2+ is rapidly oxidized by the [Fe(CN)6]3− anions, forming the soluble blue KFe3+[FeII(CN)6], and then the excess iron is gradully oxidized by atmospheric oxygen, giving an insoluble blue. 5. For the systems Fe3++[FeII(CN)6]4−, where the Fe3+ ion is taken in excess, a slow isotopic exchange Fe3+ ⇆ [Fe(CN)6]4− is detected, the occurrence of which necessitates the presence of Fe3+ ions in the system that are not contained in the insoluble and soluble blues.

Some patterns in the?-resonance and IR spectra of ferro- and ferricyanide complexes

1. Data on theγ-resonance spectra and IR spectra of iron-cyanide complexes were compared. 2. With increasing polarizing effect of the extrasphere cation, the NM bonds are strengthened on account of a shift of electrons from the antibonding orbitals of the CN group (the free pair of electrons of the nitrogen atom), which leads to strengthening of the CN bond. This influence is transmitted through the CN groups to the CFe bonds, which leads to a repulsion of electrons from the iron atom toward the CN groups. 3. In ferrocyanides the displacement occurs along the system both of σ- and of π-bonds (there is first a displacement along the system of π-bonds), while in ferricyanides it occurs chiefly along the system of σ-bonds. 4. The strengthening of the NM bonds with increasing polarizing ability of the extrasphere cation and weakening of the FeC bond from ferro- to ferricyanides produce an increase in this direction in the instability of the complex cyanides with respect to decomposition into the simple cyanides composing them.

Extraction of group VIII metals by long chain alkyl amines-V: Liquid ion-exchange behaviour of the cyanide complexes of iron, cobalt and nickel

The cyanide complexes of Fe(II), Fe(III), Co(III) and Ni(II) have been investigated with respect to their extractability by solutions of long chain alkyl amines in various solvents. The distribution of the anions, Fe(CN) 6 4− and Co(CN) 6 3− was determined by tracer methods using 59Fe and 58Co3 labelled potassium salts. For Fe(CN) 6 3− and NI(CN) 4 2− spectrophotometric methods were used. The results show the same trends as a previous study of the corresponding oxalate complexes, namely that the free base amines show virtually no extraction but good extraction is realized by using various salts of the amines. The cyanides are more readily extracted than their oxalate counterparts but the same ion-exchange behaviour is apparent.

Proton Affinities of Some Cyanide and Aromatic Diimine Complexes of Iron, Ruthenium and Osmium

<b>Proton Affinities of Some Cyanide and Aromatic Diimine Complexes of Iron, Ruthenium and Osmium</b>