A novel biphenolic ligand for selective Mg 2+ and Zn 2+ ions sensing followed by colorimetric, spectroscopic and cell imaging methods.

The (E)-2-((2-hydrohy-5-methylphenylimino) methyl) phenol ligand was synthesized. The receptor was characterized by IR, 1 H and 13 C NMR and CHN analysis. The ligand exhibits colorimetric and fluorometric sensing of Zn2+ and Mg2+ ions in semi-aqueous medium (DMSO-H2O). The receptor was tested with series of transition metal ions (Cr2+ , Fe2+ , Ni2+ , Co2+ , Cu2+ , Zn2+ ) and heavy metal ions (Sn2+ , Pd2+ , Ce2+ , Hg2+ , Cd2+ ) and the essential human body elements like Ca2+ , Mg2+ , Na+ and K+ ions. The naked eye colorimetric sensing was absorbed only for Zn2+ and Mg2+ . Both ions (ZnCl2 and MgCl2 in H2 O), when added to the colorless solutions of the receptor of about 1 equivalence in incremental additions turn the solution into bright turmeric yellow. All other ions remain inactive, in colorimetric sensing. Further the Zn2+ and Mg2+ ions were probed by absorption and emission spectroscopy through incremental addition of respective metal ions. The in-situ deprotonation of the ligand on both Mg2+ and Zn2+ ions binding was confirmed by 1 H NMR titration studies. The imino nitrogen of the receptor is not coordinated to the metal ions. The Job's plot studies reveal the 1:2 binding ratio of metal ions to the receptor. The high fold fluorescence output on metal ions binding was positively used to sense the Zn2+ and Mg2+ ions, separately and together in HeLa cancer cells through cell imaging.