Middle Phase Electrochemistry of Two Pentacyano(L)Ferrates(II)

The electrochemical behaviour of two water soluble redox species (pentacyano(L)ferrate(II) complexes, where L is 4,4\u27-bipyridine and ammonia), belonging to cyanoferrate(II) series, was investigated by using cyclic voltammetry (CV) technique in a "middle phase microemulsion" (MPME). The microemulsion (ME) is formed between water and toluene, by using, besides the redox species, sodium dodecyl sulphate as surfactant, 1-butanol as cosurfactant and sodium chloride as supporting electrolyte. Three different three-electrode configuration arrangements were used. In each case reversible behaviour for both species was obtained. Different behaviour was found in "middle phase" for the two investigated electroactive species based on the presence of the sixth ligand (coligand). The coligand determines, on one hand, different electronic influence on the electron transfer reaction at Pt working electrode and, on the other hand, specific interaction with the "microscopic organic phase" from "middle phase". This paper demonstrates, based on Randles-Sevcik equation, that [Fe(CN)5(4,4\u27–bpy)]3– is distributed between the "water phase" and "microscopic aqueous phase" rather in latter phase. For [Fe(CN)5(NH3)]3–, its distribution is similar with that of the common hexacyanoferrate(III) or hexacyanoferrate(II). The CV study of the two different electroactive species illustrates an almost reversible behaviour both in "middle phase" and "water phase". (doi: 10.5562/cca1999

Electrochemical preparation and characterisation of bilayer films composed by Prussian Blue and conducting polymer

Preparation and electrochemical behaviour of bilayer films consisting of iron(III) hexacyanoferrate, well known as Prussian Blue, and of poly[4,4′-bis(butylsulphanyl)-2,2′-bithiophene], on a platinum electrode, are reported. The electrochemical features of the Prussian Blue/conducting polymer bilayer system are examined in aqueous and acetonitrile solutions. Cyclic voltammetric studies show that, in acetonitrile solvent, the inner layer Prussian Blue is electroactive to some extent, though the electrochemical response of the system is mainly accounted for by poly[4,4′-bis(butylsulphanyl)-2,2′-bithiophene] outer layer. On the other hand, in aqueous solution Prussian Blue exhibits good electroactivity. Under specific experimental conditions, the individual redox behaviour of each constituent of the bilayer is evidenced in the two solvents separately, i.e., that of PB and that of poly[4,4′-bis(butylsulphanyl)-2,2′-bithiophene] in aqueous and in organic solvent, respectively. However, interesting reciprocal influences are evident in the current/potential curves recorded under conditions which are discussed. Keywords: Prussian Blue, Conducting polymer, Bilayer electrodes, Modified electrode

Synthesis and properties of fluorescent 4′-azulenyl-functionalized 2,2′:6′,2″-terpyridines

4′-Azulenyl-substituted terpyridines were efficiently synthesized following the Kröhnke methodology via azulenylchalcone intermediates. These azulenyl-containing terpyridines showed fluorescent emission with a fluorescence quantum yield varying from 0.14, in the case of parent terpyridine, to 0.64 when methyl groups are grafted on the azulenyl seven-membered ring. According to the crystal structures and TDDFT calculations, different twisting of the aromatic constituents is responsible for the observed fluorescent behavior. The electrochemical profile contains one-electron oxidation/reduction steps, which can only be explained on the basis of the redox behavior of the azulene unit. The ability of the 4′-azulenyl 2,2′:6′,2″-terpyridine to bind poisoning metal cations was studied by UV–vis titrations using aqueous solutions of Hg(II) and Cd(II) chlorides as illustrative examples

Development of Amperometric Biosensors Based on Nanostructured Tyrosinase-Conducting Polymer Composite Electrodes

sensor