Preparation and characterisation of electrodes modified with iron porphyrins immobilised in a poly(amino acid) matrix

Abstract

Controlled reaction of 1-(3-aminopropyl)imidazole with poly(γ-ethyl L-glutamate) leads to conversion of some side-chain ester groups to amides. The functionalised polymer is characterised by ¹H NMR spectroscopy. Imidazole complexes have been formed between this functionalised polymer and 5,10,15,20-tetraphenylporphyrin iron(III) chloride and also deuteroporphyrin-IX dimethyl ester iron(III) chloride. Films of the polymer-porphyrin complexes formed on platinum and on tin oxide coated glass show reversible redox activity in acetonitrile and in aqueous electrolytes. Both redox states of iron are characterised as bis-imidazole ligated by their UV–VIS spectra. The influence of the degree of polymerisation of the starting poly(γ-ethyl L-glutamate), the composition of the aqueous electrolyte and the oxidation state of the iron centre on the stability of the hydrogel films towards redox cycling is examined.