A novel biphenolic ligand for selective Mg and Zn 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, H and C NMR and CHN analysis. The ligand exhibits colorimetric and fluorometric sensing of Zn and Mg ions in semi-aqueous medium (DMSO-H2O). The receptor was tested with series of transition metal ions (Cr, Fe, Ni, Co, Cu, Zn) and heavy metal ions (Sn, Pd, Ce, Hg, Cd) and the essential human body elements like Ca, Mg, Na and K ions. The naked eye colorimetric sensing was absorbed only for Zn and Mg. Both ions (ZnCl and MgCl in HO), 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 Zn and Mg ions were probed by absorption and emission spectroscopy through incremental addition of respective metal ions. The in-situ deprotonation of the ligand on both Mg and Zn ions binding was confirmed by 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 Zn and Mg ions, separately and together in HeLa cancer cells through cell imaging.