Hexacyanoferrate Anions Research Articles

Redox anion doped polypyrolle films; electrochemical behaviour of polypyrrole prepared in Fe(CN) 6 solution

Polypyrrole films were formed with hexacyano-ferrate (HCF) anions as exclusive dopants. It was observed that a portion of the built-in HCF displayed reversible electro-chemistry, but the majority of the doping anions are non-electroactive, while they are inside the polymers. Calculations showed that one excess positive charge on the polymer backbone was compensated by one HCF ion, thus, the entrapment of these multivalent anions was accompanied by the inclusion of a large amount of cations as well. These films were sensitive for the size of the cations present in the solution.

Effect of the water of crystallization on the Mössbauer spectra of hexacyanoferrates (II and III)

Mossbauer spectra were recorded on hydrated, dehydrated and rehydrated hexacyanoferrate (II and III) samples including alkaline, alkaline-earth, transition metal and rare-earth salts. The location of the water molecules around the complex hexacyanoferrate anion has a decisive role on the quadrupole splitting of the low-spin FeIII cation.

Effects of temperature on the photo-oxidation quantum yield of aqueous hexacyanoferrate(II) anion

The photo-oxidation quantum yield of aqueous hexacyanoferrate(II) anion in the presence of N2O is found to be moderately dependent on temperature at 253.7 nm, but at 228.8 nm only very slightly dependent, and with a substantially lower quantum yield. In considering models of the photoionization process, it is deduced that, at least at the lower wavelength of irradiation, the charge-transfer metal-to-ligand state produced by light absorption does not quantitatively populate the CTTS state believed to be the intermediate in solvated electron production. At 253.7 nm, where the slope of the plot of In(Φ–1e–– 1) against T–1 is somewhat less than for iodide ion, the involvement of some other fate for the CTML state (but to a much lesser extent than at the higher quantum energy) is a clear possibility.

Bioavailability of Iron and Cyanide from 59Fe-and 14C-Labelled Hexacyanoferrates(II) in Rats

"Soluble" (KFe(III)[Fe(II)(CN)6]) and "insoluble Prussian blue" (Fe(III)4[Fe(II)(CN)6]3 labelled with 59Fe either in the ferric (Fe(III)) or ferro (Fe(II)) position and 14C in the cyanide group were synthesized and administered intraperitoneally or orally to adult female rats with normal body iron stores. Following i.p. injection of KFe[Fe(CN)6], the colloidal complex is disintegrated into ferric iron and hexacyanoferrate(II) anion almost completely. About 96% of the ferric iron was retained in the body. Nearly 90% of both ferrous iron and cyanide were excreted with the urine within 7 days after i.p. injection, indicating that most of the undissociated hexacyanoferrate(II) anion ([Fe(CN)6]4-) was excreted through the kidney. Only 9% of the ferrous iron from [Fe(CN)6]4- was found mainly in carcass, liver and gut. As the 59Fe/14C-ratios in organs were found close to 1.0, the dissociation of the hexacyanoferrate(II) anion can only be small in vivo. No detectable 14CO2-activity (less than 0.01%) was monitored in the breath of rats after i.p. injection of the 14C-labelled KFe[Fe(CN)6], also indicating that no significant amounts of cyanide were released after parenteral administration. After oral administration of the soluble and insoluble Prussian blue, 0.3-0.7% of the ferric iron was absorbed and retained mainly in carcass, liver and blood. Only 0.06-0.18% of the ferrous iron was absorbed and mostly excreted with the urine (0.05-0.15%), so that only 0.01-0.03% of the oral ferrous 59Fe was retained in the body after 7-10 days. Very small fractions of 14C-label from the 14CN-group of the soluble and insoluble hexacyanoferrate(II) were observed in the exhaled air (0.04-0.08% of the oral dose). From the 14CO2-exhalation, the 14C-urine excretion and the distribution of iron in blood and organs it can be concluded that the hexacyanoferrate(II) moiety disintegrated only to a small extent in the intestinal tract after oral administration. From a dose of 36 mg hexacyanoferrate(II)/kg, an amount of free (non-complex bound) cyanide can be calculated which is in maximum two orders of magnitude below the LD100-level. Thus, the very low bioavailability of iron and cyanide from hexacyanoferrate(II) compounds after oral application is demonstrated in rats. In the case of a severe nuclear accident, appropriate doses of "soluble" and "insoluble" Prussian blue can be used as safe and effective antidote against radiocaesium contamination.

Anion coordination chemistry. Hexacyanoferrate(II) anion complexed by a large polycharged azacycloalkane. Potentiometric and electrochemical studies

Etude des interactions entre l'anion hexacyanoferrate(II) et le macrocycle heptaazacycloheneicosane. Constantes de stabilite des complexes en solution aqueuse

Solvent effects on redox potentials studies in N-methylformamide

The redox behaviour of LiClO 4 , NaClO 4 , KClO 4 , RbClO 4 , CsClO 4 , TiClO 4 , Ba(ClO 4 ) 2 , Cu(CF 3 SO 3 ) 2 , Cd(CF 3 SO 3 ) 2 , Zn(CF 3 SO) 2 , Zn(ClO 4 ) 2 ·2 H 2 O, (Et 4 N) 3 Fe(CN) 6 , (Bu 4 N) 3 Fe(CN) 6 , (Et 4 N) 3 Mn(CN) 6 , (Bu 4 N) 3 Mn(CN) 6 , ferrocene (biscyclopentadienyl-iron(II), bis(biphenyl)chromium tetraphenylborate and perylene has been studied in N-methylformamide employing polarography and cyclic voltammetry. Standard redox potentials have been estimated from polarographic half wave potentials—measured versus bis(biphenyl)chromium as a reference redox system—of reversible or nearly reversible electrode processes. The data have been compared with the redox potentials versus bis(biphenyl)chromium in formamide and N,N-dimethylformamide. Since the dielectric constants of these three solvents differ considerably, models for the correlation of redox potentials with solvent parameters have been evaluated with regard to their ability to predict differences in redox potentials of a given system in these solvents. Purely electrostatic concepts could not account for the observed changes in redox potentials from one solvent to another. Considering interactions of the solvent molecules as donors with cations as acceptors yielded a good correlation between the donor number of the solvents and the redox potentials for cations that were reduced to the respective metal amalgams. The redox potentials of the hexacyanomanganate and hexacyanoferrate anions were found to be a function of the acceptor properties of the solvents.

Solvent effects on redox potentials: Studies in N-methylformamide

The redox behaviour of LiClO 4, NaClO 4, KClO 4, RbClO 4, CsClO 4, TiClO 4, Ba(ClO 4) 2, Cu(CF 3SO 3) 2, Cd(CF 3SO 3) 2, Zn(CF 3SO) 2, Zn(ClO 4) 2·2 H 2O, (Et 4N) 3 Fe(CN) 6, (Bu 4N) 3Fe(CN) 6, (Et 4N) 3 Mn(CN) 6, (Bu 4N) 3 Mn(CN) 6, ferrocene (biscyclopentadienyl-iron(II), bis(biphenyl)chromium tetraphenylborate and perylene has been studied in N-methylformamide employing polarography and cyclic voltammetry. Standard redox potentials have been estimated from polarographic half wave potentials—measured versus bis(biphenyl)chromium as a reference redox system—of reversible or nearly reversible electrode processes. The data have been compared with the redox potentials versus bis(biphenyl)chromium in formamide and N,N-dimethylformamide. Since the dielectric constants of these three solvents differ considerably, models for the correlation of redox potentials with solvent parameters have been evaluated with regard to their ability to predict differences in redox potentials of a given system in these solvents. Purely electrostatic concepts could not account for the observed changes in redox potentials from one solvent to another. Considering interactions of the solvent molecules as donors with cations as acceptors yielded a good correlation between the donor number of the solvents and the redox potentials for cations that were reduced to the respective metal amalgams. The redox potentials of the hexacyanomanganate and hexacyanoferrate anions were found to be a function of the acceptor properties of the solvents.

Ion association and charge-transfer excitation between N-heterocyclic cations and cyanoiron complexes

N-Heterocyclic cations form with substituted pentacyanoferrates a series of outer-sphere complexes of general formula Fe(CN)5L//N-Het, suitable for systematic studies in aqueous solution. The equilibrium constants for the association of dipositive cations (e.g. N,N′-dimethyl-4,4-bipyridyl, or paraquat ion) and monopositive cations (e.g. N-methylpyrazinium) with the hexacyanoferrate(II) anion are typically in the range of 30–40 M−1and 10–13 M−1. The optical charge-transfer energies depend on the nature of the N-heterocyclic acceptor, and on the binding properties of the ligand L as they modify the ionization potentials of the Fe(CN)5Ln− complexes. A linear correlation between the optical charge-transfer energies and ΔE0 was found, with a slope (ΔEop/ΔG0) of 1.03 ± 0.03. The results were interpreted on the light of Hush's theory for intervalence transitions, with the aid of the equation Eop = 2(ΔG11* + ΔG22*) + ΔG120, which correlates the optical energy (Eop) for electron-transfer with the intrinsic barriers (ΔG11* + ΔG22*) of the donor and acceptor ions, and the free energy change (ΔG120) for the process.

Removal of Hexacyanoferrate from Selected Photographic Process Effluents by Ion Exchange

An ion-exchange process has achieved almost complete removal of hexacyanoferrate anion Fe(CN) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> from the bleach wash of Eastman color-print processes that use ferricyanide bleaches. A weak-base, gel-type resin column that has an adsorption capacity of approximately 50 g of Fe(CN) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> per liter of wet resin was used. For resin regeneration, the hexacyanoferrate was eluted from the resin with sodium hydroxide, and the resulting solution was then oxidized for use as a bleach replenisher. This technique provides a route to complete recovery and recycling of the ferricyanide. Similar treatment was also applied to a final wash of Process K-14 for Kodachrome films, with equal success in removal of the hexacyanoferrate. However, reuse of the ferrocyanide recovered by this process is complicated by the presence of thiosulfate anion which is also removed from the effluent by the resin.

Kinetics of the oxidation of formazans. I. Hexacyanoferrate(III) oxidations

A study is reported of the hexacyanoferrate(III) oxidations of several formazans in ammonia containing solutions. The reactions were performed in water as well as in ethanol (45.5 wt%) water mixtures at a temperature of 25°C and at an ionic strength of 0.09. With only one exception the reactions appeared to be first order in the formazan, hexacyanoferrate(III) and ammonia. Variation of the ammonium nitrate concentration at constant ionic strength revealed two competing reactions: oxidation by the Fe(CN) 6 3− and by the NH 4Fe(CN) 6 2− anion. The predominant reaction was found to be the oxidation of the formazan anion by the hexacyanoferrate(III) anion.

Infrared Spectroscopic Study on Ion Association of Hexacyanoferrate(III) and Hexacyanoferrate(II) Ions

Abstract The ion association of hexacyanoferrate(III) and hexacyanoferrate(II) anions with univalent or bivalent cations in aqueous solutions has been studied by the measurement of the infrared absorption band due to the C≡N stretching vibrations. All the solutions measured in which ion-pairs with hexacyanoferrates(III) predominated gave an absorption maximum at 2121 cm−1, and those in which ion-pairs with hexacyanoferrates(II) predominated, at 2020 cm−1, although hexacyanoferrates(III) and hexacyanoferrates(II) of potassium and alkaline earth metals gave different spectra from each other in solid state. No difference in absorption band obtained with different solutions was supported by the distance between two ions in ion-pair, which was estimated from the structures of hexacyanoferrate(III) and hexacyanoferrate(II) ions and the closest approach of the ion-pair; this indicates that there is no direct interaction between the complex anion and the cation, but one or more water molecules interpose between the two ions.