A cation selective electrode based on copper(II) and nickel(II) hexacyanoferrates: dual response mechanisms, selective uptake or adsorption of analyte cations

Porous Hexacyanometallate(III) Complexes as Catalysts in the Ring-Opening Copolymerization of CO2 and Propylene Oxide

In this work, six porous hexacyanometallate complexes (Ni3[Co(CN)6]2, Co3[Co(CN)6]2, Fe3[Co(CN)6]2, Ni3[Fe(CN)6]2, Co3[Fe(CN)6]2, Fe4[Fe(CN)6]2) were synthesized by a complexing agent assisted coprecipitation method and thoroughly characterized via X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), in situ high-temperature X-ray diffraction (HT-XRD), elemental analysis (EA), X-ray fluorescence (XRF), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 physisorption, and gas–solid phase titration with NH3. The thermal stability, chemical composition, pore size and volume, crystallite size and density of surface acid sites were strongly sensitive to both the transition metal and the cyanometallate anion employed. On that basis, transition metal hexacyanometallates must be perceived as an adaptable class of zeolite-like microporous materials. The catalytic properties of these compounds were tested by copolymerization of propylene oxide and CO2, a green route to obtain biodegradable aliphatic polycarbonates. All compounds under study showed moderate activity in the target reaction. The obtained copolymers were characterized by modest CO2 content (carbonate units ranging from 16 to 33%), random structure (RPEC ≈ 70%), and moderate molecular weight (Mw = 6000–85,400 g/mol) with broad dispersity values (ĐM = 4.1–15.8).

Electronic Communication in Luminescent Dicyanorhenate-Bridged Homotrinuclear Rhenium(I) Complexes

A series of cyano-bridged homotrinuclear Re(I) complexes with the general formula of {[Re]'[Re][Re]'}⁺ {[Re]' = -[Re^I(CO)₂(LL)(X)]; [Re] = -[(NC)Re^I(CO)₂(phen)(CN)]-; LL = diimine, diphosphine, or two carbonyl ligands; X = triphenylphosphine or carbonyl ligand} and the corresponding mononuclear complex analogues were synthesized. The structures of most of the trinuclear Re(I) complexes have been determined by X-ray crystallography. The relative orientations of peripheral to central Re(I) units in these structures vary considerably. The photophysical properties of these trinuclear Re(I) complexes have been examined. Except for the trinuclear Re(I) complex with Br₂phen ligand, all the other triads display orange to red photoluminescence derived from the ³MLCT [dπ(Re) → π*(phen)] origin of the central Re(I) unit, suggestive of efficient energy transfer between the peripheral chromophores and the central unit. In addition to the efficient energy transfer processes between the Re(I) chromophores in these trinuclear complexes, the ability of the [NC-Re-CN] bridging ligands for electronic coupling between the rhenium metal centers is evidenced by ca. 0.2-0.3 V separation of the two rhenium metal-based oxidation potentials of the chemically equivalent peripheral units.

New faces of porous Prussian blue: interfacial assembly of integrated hetero-structures for sensing applications

Prussian blue (PB), the oldest synthetic coordination compound, is a classic and fascinating transition metal coordination material. Prussian blue is based on a three-dimensional (3-D) cubic polymeric porous network consisting of alternating ferric and ferrous ions, which provides facile assembly as well as precise interaction with active sites at functional interfaces. A fundamental understanding of the assembly mechanism of PB hetero-interfaces is essential to enable the full potential applications of PB crystals, including chemical sensing, catalysis, gas storage, drug delivery and electronic displays. Developing controlled assembly methods towards functionally integrated hetero-interfaces with adjustable sizes and morphology of PB crystals is necessary. A key point in the functional interface and device integration of PB nanocrystals is the fabrication of hetero-interfaces in a well-defined and oriented fashion on given substrates. This review will bring together these key aspects of the hetero-interfaces of PB nanocrystals, ranging from structure and properties, interfacial assembly strategies, to integrated hetero-structures for diverse sensing.

Mechanism for interplay between electron and ionic fluxes in KhFek[Fe(CN)6]l.mH2O compounds

This paper develops a framework for the interpretation of ionic insertion/deinsertion reactions in an aqueous environment taking place in transition-metal hexacyanoferrates of the general formula K(h)[Fe(2+) (CN)(6)](l).mH(2)O, also called Prussian Blue. Three different processes were fully separated in the electrochemistry of these films. It was clearly identified that one of these electrochemical processes involves the insertion/deinsertion of H(3)O(+) (hydrated protons) through the channels of the K(h)[Fe(2+) (CN)(6)](l).mH(2)O structure to reach the film electroneutrality during the electron transfer between Everitt's Salt and Prussian Blue. The other electrochemical processes involve K(+) or H(+) (proton) exchange through the water crystalline structure existing in the channels of the K(h)[Fe(2+)(CN)(6)](l).mH(2)O structure.

An amperometric hydrogen peroxide sensor based on immobilization of hemoglobin in poly(o-aminophenol) film at iron–cobalt hexacyanoferrate-modified gold electrode

A series of hybrid iron-cobalt hexacyanoferrate (FeCoHCF) films were electrodeposited on gold electrodes from solutions containing 6mM Fe(CN)(6)(3-) with different concentrations of Co(2+) and Fe(3+). FeCoHCF films deposited from solutions with different molar ratios of iron were studied by cyclic voltammetry, and their solid states were characterized by Fourier transform infrared spectroscopy. The kind of FeCoHCF film that deposited from a solution with a molar ratio of iron of 0.4 showed the largest response current to H(2)O(2) and was characterized by energy-dispersive X-ray spectroscopy. Therefore, the optimized FeCoHCF film was combined with nonconducting poly(o-aminophenol) (POAP) film that entrapped the hemoglobin (Hb) to construct hydrogen peroxide biosensor. The response current of the Hb/POAP/FeCoHCF/Au electrode (29.8 nA) was nearly 40 and was 1.5 times that of the Hb/POAP/Au (0.7 nA) and POAP/FeCoHCF/Au (20 nA) electrodes, respectively. The Michaelis-Menten constant of Hb in the Hb/POAP/FeCoHCF/Au film was 9.31 mM. These results show that the immobilized Hb in the Hb/POAP/FeCoHCF/Au film exhibits higher catalytic activity and larger response current to H(2)O(2) by the mediation of FeCoHCF. In addition, effects of applied potential, solution pH, and electroactive interferent on the response current of the Hb/POAP/FeCoHCF/Au electrode were investigated in detail.

Investigation of the effects of Au-colloid modification on cobalt hexacyanoferrate film growth and mass transport by electrochemical quartz crystal microbalance

The growth of cobalt hexacyanoferrate (CoHCF) films on bare and Au-colloid-modified electrodes in nitrate or sulfate solutions was monitored by electrochemical quartz crystal microbalance. The average efficiency of CoHCF film growth for Au colloid modified electrodes is 23 and 12 ng cm(-2) s(-1) in KNO3 and K2SO4 solutions, respectively, while those values for the bare gold electrode are 15 and 9 ng cm(-2) s(-1), respectively. In K2SO4 solution, the apparent molar masses for the Au-colloid-modified electrode at lower and higher potential is 58.4 and 37.3 g mol(-1), respectively, which is larger than those for the bare gold electrode (51.7 and 26.3 g mol(-1), respectively). The respective results were also obtained in KNO3 solution. Furthermore, the difference of the apparent molar masses at lower and higher potential for Au-colloid-modified electrodes is smaller than that for bare gold electrodes in the same electrolyte. Additionally, the mechanism of charge propagation is dependent on different anions in electrolyte solutions at higher potentials where the second redox reaction of CoHCF occurs. Therefore, the existence of Au colloids can accelerate CoHCF film growth and weaken the effect of anions on mass transport.