Development of a fluorescent chemosensor towards sensing and separation of Mg2+ ions in chlorophyll and hard water

A dyad bearing a disulfide spacer and a naphtholyl terminal group with imine functionality has been synthesised (compound LH2) and assessed for its metal ion binding ability in an aqueous medium. This receptor molecule selectively binds Mg2+, with an enhancement in fluorescence intensity of the band at 550 nm. The results show a turn-on response for Mg2+ binding through a PET mechanism. The photophysical properties of the receptor in different solvents, at various pH values and with various metal ions are studied. The receptor molecule shows visible sensing for Mg2+ ions in a (Cynodon dactylon) plant leaf extract which contains chlorophyll. Also, a polysulphone memberane is prepared by incorporating the receptor in it and used for filtering water containing an excess of Mg2+ ions. Fluorescence signal output-based molecular logic gates (NOR, X-NOR) are proposed using H+ and Mg2+ ions as inputs into the molecule.