On the oxidation of Wurster’s reagent and the Wurster’s crown analog of 15-crown-5 in the presence of alkali metal cations

Experimental evidence of the – electrochemically controlled – release of an alkali metal cation from the cage of a substituted crown ether has been obtained through the use of in situ FTIR spectroelectrochemistry. Crown ethers have been modified by grafting an electroactive para-phenylenediamine moiety to a macrocyclic framework to generate the class of compounds known as the “Wurster’s Crowns”. These ligands exist in three discrete oxidation states and, as such, behave as redox-active complexing agents. Their electrochemistry shows two reversible one-electron oxidations that were studied in situ by FTIR and UV–visible spectroelectrochemistry. Of the two techniques, only FTIR provides information on the interaction of alkali metal cations with the crown ether as well as evidence that in the dicationic state of the molecule, cations were no longer tied to the crown ether. DFT simulation of infrared spectra was successfully used to attribute vibrational motions to the experimentally observed frequencies.