Recognition of metal cations with surface immobilized crown ether functionalized poly(ferrocenylsilane)

For the design of an electrochemical sensor, a functionalized benzo-18-crown-6 is required for the attachment to iodopropyl-functionalized poly(ferrocenylsilane) (PFS). Various acylation reactions were investigated, as this was the crucial step in view of obtaining a clean product of hydroxyl-functionalized benzo-18-crown-6. The different reactions were carried out at 50°C or room temperature using solid catalysts and acids. The acylation performed at room temperature using Eaton’s reagent as catalyst yielded 69% of 4’-acetylbenzo-18-crown-6 without by-products. 4’-Hydroxybenzo-18-crown-6 could be obtained after the Baeyer-Villiger oxidation and hydrolysis, with 17% of unfunctionalized crown ether startingmaterial present. The electrochemical sensor, consisting of 4’-aminobenzo-18-crown-6 attached to a PFS-modified gold substrate, was successfully tested since it responded to very low potassium ion concentrations in aqueous solution.