The electrochemistry of tetraphenyl porphyrin iron(III) within immobilized droplets supported on platinum electrodes

Journal article

For the first time, the voltammetry of an ensemble of immobilized benzonitrile microdroplets containing 5,10,15,20-tetraphenyl-21H,23H-porphine iron (III) chloride, TPPFeCl immobilized at platinum electrodes immersed in various aqueous electrolytes has been explored. The reduction of TPPFeCl was observed with the voltammetric response seen to be highly dependent on the nature of ions in the surrounding aqueous phase. Unlike voltammetry in purely homogeneous solution the nature of the aqueous electrolyte can influence the voltammetry in the droplet phase. The electrochemical reduction of TPPFeCl contained within tetrabutylammonium chloride (TBACl) supported benzonitrile (PhCN) microdroplets immersed into an aqueous solution of TBACl was first studied. During TPPFeCl reduction the resulting [TPPFeCl]- species is stabilized due to the excess of chloride anions inside the oil droplet. Voltammograms of homogeneous solutions of PhCN supported with TBACl show similar chemically reversible process which is also attributed to the stable [TPPFeCl]- species. This anion stabilization was not observed when the oil droplets were supported with tetrabutylammonium perchlorate (TBAP) or when the PhCN solution bathing the microdroplet ensemble was supported with TBAP resulting in a chemically irreversible process. The voltammetry of unsupported droplets immobilized on a platinum electrode immersed in different aqueous electrolytes was also explored and the fate of the [TPPFeCl]- species formed considered during the reduction sweep. Similarities and difference to voltammetry in purely homogeneous media are noted and the use of droplet voltammetry provides complimentary information. © 2006 Wiley-VCH Verlag GmbH and Co. KGaA.

Authors: Munoz, R; Banks, C; Davies, T; Angnes, L; Compton, R

• Publication status: Published
• Journal: ELECTROANALYSIS
• Volume: 18
• Issue: 7
• Pages: 649-654
• Publication date: 2006-04-01
• DOI: 10.1002/elan.200503460
• EISSN: 1521-4109
• ISSN: 1040-0397
• Language: English
• Keywords: three phase boundary; iron(III) porphyrin; oil microdroplets; liquid-liquid interface; modified electrodes; Fe(III)/Fe(II) reduction; lon transfer