The metal-ligand complex 1 ([Mg (L)] (2+)) (or 2 ([Ca (L)]( 2+))) was demonstrated to selectively bind HSO(4)(-) (or H(2)PO(4)(-)) over other anions by using UV-vis absorption and fluorescence spectroscopy. The studied complex exhibits the remarkable color change and fluorescence quenching upon introducing HSO(4)(-) (or H(2)PO(4)(-)) anion in acetonitrile. Both the mechanism and structure of the secondary complex of complex 1 with anion were proposed on the basis of theoretical computation.