In pursuit of the ideal chromoionophores (part II): The structure-property relationship for electrochemical signaling capacities of aza-12-crown-4 ethers substituted with an anthraquinone moieties

The manuscript presents the electrochemical characteristics of aza-12-crown-4 ethers substituted with an anthraquinone moiety. The pH-spectroscopic dependencies of these dyes have already been proven by us (part I). The aim of this work is to demonstrate pH-dependent electrochemical signaling capabilities of these ethers, which may be utilized as an alternative to their optical ones. This dualistic signaling nature makes the presented group of compounds potentially very attractive molecular recognition systems. Therefore, the detailed discussion of the effect of the structure of the macrocycle on the mechanism of electrode reactions provided here, seems to be crucial, as it may allow to design other systems of such diverse capabilities. The sensitivity of the electro-phores to interactions with protons was thoughtfully scrutinized. Voltametric measurements presented new phenomena: the formation of three reduction peaks, which is unusual for quinones. Quantum chemical simu-lations allowed the attribution of these effects to the presence of amino groups in the macrocycle and their ability to form intramolecular hydrogen bonds. The combination of electrochemical, spectroscopic and acid-base properties of the studied compounds clearly demonstrates their versatility and potential applicability in new sensors.