Chlorination and Oxygenation of Carbon Electrodes for Covalent Attachment of Thiol-Terminated Molecules

This study investigated the reactivity of two carbon electrodes (glassy carbon - GC and carbon powder - CP), with iodine monochloride for surface chlorination and subsequent covalent attachment of thiol-terminated molecules, (6-mercaptohexyl)ferrocene and benzene-1,2,4,5-tetrathiol. X-ray photoelectron spectroscopy analysis revealed that the iodine monochloride treatment resulted in chlorination and iodination of both carbon electrodes, with post-reaction GC exhibiting significant Cl:C ratios. However, chlorination of either carbon electrode did not enhance reactivity with thiol-terminated molecules. For GC, inherent or anodized surface oxide groups were found to be equally effective for covalent attachment of thiol-terminated molecules through Michael addition as chlorine-termination through nucleophilic aromatic substitution. In contrast, CP, despite its lower surface reactivity, could directly tether (6-mercaptohexyl)ferrocene without pretreatment or chlorination. Furthermore, a tetrathiolate bridge was successfully employed to covalently attach a molybdenum complex to anodized GC.