THIOL-DERIVATIZED METALLOPORPHYRINS - MONOMOLECULAR FILMS FOR THE ELECTROCATALYTIC REDUCTION OF DIOXYGEN AT GOLD ELECTRODES

This paper describes preliminary results in the design, construction, and characterization of cobalt(II) porphyrins derivatized with alkanet hiol appendages. The use of the thiol appendages leads to the formatio n of a chemisorbed monolayer of the corresponding thiolate at gold ele ctrodes. Our findings suggest that this approach may serve as a beginn ing for fabricating electrocatalytic monolayers with a preselected arc hitecture through the manipulation of the number and location of the a ppendages. Voltammetric data indicate that monolayers from both I(Co) and II(Co) catalyze the two-electron reduction of O2 to H2O2. The mono layer from I(Co), however, has a lower electrocatalytic activity. Infr ared, X-ray photoelectron, and visible spectroscopic data are presente d that argue the difference in reactivity arises from a difference in interfacial architecture. The results from attempts to metalate monola yers from I(H-2) and II(H-2) support this interpretation. Findings are also reported that indicate the preparation of mixed monolayers (e.g. , two-component monolayers from I(Co) and CH3(CH2)3SH) may prove valua ble to this area of research.