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The Os 2+ functionalised pyrrole monomer, Osmium-bis-N,N'-(2,2'-bipyridyl)-N-(pyridine-4-ylmethyl-(8-pyrrole-1yl-octyl)-amine)chloride, 1, has been synthesised and characterised by spectroscopic (UV/Vis, 1 H NMR, IR spectroscopy) techniques and cyclic voltammetry.Solution phase studies of 1 gave a redox couple associated with the Os 3+/2+ and an irreversible wave associated with the oxidation of the pyrrole moiety. Attempts to form stable polymeric films of 1 onto vitreous carbon electrodes, by homopolymerisation, proved unsuccessful. However electroactive films of 1 were obtained by the electrooxidation of 1 through the Os 3+/2+ couple in low dielectric media such as toluene/acetonitrile mixtures.

Copolymerisation of an Osmium (II) functionalised pyrrole moiety, Osmium -bis-N,N'-(2,2'-bipyridyl)-N-(pyridine-4-ylmethyl-(8-pyrrole-1yl-octyl)-amine)chloride(1) with 3-methylthiophene was carried out. The resulting conducting polymer film exhibited a clear redox couple associated with the Os 3+/2+ response and the familiar conducting polymer backbone signature. The effect of film thickness upon the redox properties of the copolymer was investigated in organic electrolyte solutions. Scanning electron micrographs (SEM) along with energy dispersive X-ray (EDX) spectra of the copolymerised films were undertaken, both after formation and redox cycling in neutral buffer solution. These clearly show that electrolyte is incorporated into the polymer film upon redox cycling through the Os 3+/2+ redox system. The Os 3+/2+ response associated with the copolymer was seen to be significantly altered in the presence of ascorbic acid both in acidic and neutral pH buffer solutions. This pointed to an electrocatalytic reaction between the ascorbic acid and the Os 3+ form of the copolymer. Under acidic conditions the copolymer film exhibited a sensitivity of 1.76 (± 0.05) uA / mM with a limit of detection (LOD) of 1.45 µM for ascorbic acid. Under neutral pH conditions the copolymer exhibited a sensitivity of 19.26 (±1.05) uA / mM with a limit of detection (LOD) of 1.28 µM for ascorbic acid.Keywords: Osmium, Pyrrole, Copolymerisation, ascorbic properties of an Os(II) functionalised pyrrole monomer, namely, osmium-bis-N,N'-(2,2'-bipyridyl)-N-(pyridine-4-yl-methyl-(8-pyrrole-1-yl-octyl)-amine) chloride (1). Attempts to polymerise this pyrrole monomer proved unsuccessful probably due to the closeness of the bulky Os(II) bipyridyl moiety to the pyrrole ring. Our interest lies in the surface immobilisation of 1 through the employment of the well known copolymerisation technique. In terms of copolymerisation, the conducting polymer of choice has been polypyrrole [17,18], this being primarily due to its "low oxidation potential" and "high conductivity" [19]. However recently thiophenes and its derivatives have been explored as possible matrixs for copolymerisation [20][21][22]. In this paper we report on the successful copolymerisation of 1 with 3- Apparatus and ProceduresElectrochemical experiments were performed in a single compartment three-electrode cell.The reference electrode employed, for the organic phase electrochemistry, was a silver wire . This ratio between 1 and the 3-MTHP was found to be ideal. Previous experiments were attempted with a range of 1:3MTHP ratios being employed (i.e.: 5mM:5mM; 2.5mM:10mM; 3mM:20mM; 3mM;30mM; 5mM:40mM; 5mM:10mM). However it was found that these films all exhibited either poor stability or low redox loadings of the Os 2+ centre. After formation, each film was rinsed with the solvent-electrolyte system that its electrochemical behaviour was going to be investigated in. Scanning electron microscopy (SEM) was performed using a Hitachi S-2400N system. For SEM investigations, films were ...

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A ruthenium(II) functionalized pyrrole, Ruthenium-bis-N,N'-(2,2'-bipyridyl)-N-(pyridine-4-ylmethyl-(8-pyrrole-1-yloctyl)amine)chloride, 1, has been synthesized and characterized by spectroscopic (UV/vis, 1 H NMR) techniques and cyclic voltammetry. In solution 1 gave a redox couple associated with the Ru 3þ/2þ redox system and an irreversible wave associated with the oxidation of the covalently linked pyrrole moiety. What is believed to be homopolymerization, redox active surface films of 1 have been prepared by electrooxidation of the monomeric solution. The resulting polymeric film exhibited clear redox activity associated with the incorporated Ru 2þ redox centre, which is covalently linked ruthenium centre to the pyrrole moiety in 1. The effect of surface coverage upon the electrochemical behavior of the deposited films has been undertaken. Preliminary investigations into the homogeneous charge transport dynamics of the polymeric film deposited onto platinum microelectrodes has been undertaken. Copolymerization with 3-methylthiophene was carried out and a clear ruthenium response was seen. Films were formed by both cyclic voltammetry and chronocoulometry and studied. Various ratios were attempted but the ideal was found to be 52 : 5 mmol (3-methylthiophene: 1).

The corrosion performance and electrical contact resistance were investigated for a trivalent chromium passivation layer and a cobalt-free version of that same passivation layer on γ-ZnNi-coated Al 6061-T6. Both passivation layers had a similar surface morphology, were amorphous, had similar thicknesses, and contained pores within the passivation layer. The cobalt-containing passivation layer initially had an exchange current density of 9.5 × 10–4 A/cm2 and a polarization resistance of 290 Ω/cm2. The cobalt-free passivation layer initially had an exchange current density of 10.6 × 10–4 A/cm2 and a polarization resistance of 116 Ω/cm2. After 500 h of exposure to neutral salt spray, the cobalt-containing passivation layer showed no visible corrosion and had an exchange current density of 2.9 × 10–4 A/cm2 and a polarization resistance of 136 Ω/cm2. The cobalt-free passivation layer showed uniform corrosion and had an exchange current density of 5.2 × 10–4 A/cm2 and a polarization resistance of 80 Ω/cm2. After 500 h of exposure to neutral salt spray on specimens which were scribes down to the Al substrate, the cobalt-free passivation layers were uniformly corroded, but scribed specimens with the cobalt-containing passivation layers were only partially corroded. Both the cobalt-containing and cobalt-free passivation layers were found to be viable alternatives to hexavalent chromium as per the requirements of cobalt-containing MIL-DTL-81706 offering protection comparable to hexavalent chromium and cobalt-free offering less. The presence of cobalt in the TCP layer was found to improve corrosion performance and suggested that an intermediate species such as cobalt is beneficial to the oxidation of Cr­(III) to Cr­(VI).