A simple aza-crown ether containing an anthraquinone fluorophore for the selective detection of Mg(II) in living cells

A new aza-crown ether anthraquinone-coupled chemosensor (2) has been synthesized and employed for the selective fluorescence detection of Mg(II) in the nanomolar range with limited interference by Ca(II) ion. The binding stoichiometry for the chemosensor with Mg(II) is found to be 2:1, and the binding constant was determined to be 2.9×109 M−2 and 5.1×109 M−2 in acetonitrile and DMSO, respectively. The chemosensor also shows negligible fluorescence enhancement from other alkali, alkaline earth, and transition metals. Chemosensor 2 has been used in the bioimaging of Mg(II) in embryonic mouse fibroblast NIH3T3 cells at both native concentrations and cells incubated with excess Mg(II). The chemosensor can access Mg(II) ions in both the cytoplasm and nucleus of the cells. The corrected total cell fluorescence is also calculated to confirm the uptake of the chemosensor in living cells.