Biphenyl-containing amido Schiff base derivative as a turn-on fluorescent chemosensor for Al3+ and Zn2+ ions

A hydrazine-derived bis(2-hydroxybenzylidene)-[1,1'-biphenyl]-2,2'-dicarbohydrazide (sensor 1) has been synthesized and its sensing properties toward metal ions have been demonstrated using simple UV-visible spectroscopy, fluorometry and visible color change techniques. The sensor 1 showed high fluorescence selectivity and sensitivity toward Al3+ and Zn2+ ions in aqueous DMF media. The fluorescence intensity of 1 increases in the presence of Al3+ at 458 nm and in the presence of Zn2+ at 478 nm. Visual color change under 350 nm UV light exhibits a bluish-white and bluish-yellow fluorescence light in the presence of Al3+ and Zn2+ ion, respectively. The ESI-MS and Job's plot analysis show that sensor 1 and metal ions formed a 1: 2 coordination complex. A fluorescenct switch based on the control of Zn2+ and EDTA proved that sensor 1 could act as a reversible chemosensor. However, on the addition of the EDTA into 1-Al3+ complex, there was no spectral change and naked-eye color change was observed. The sensing behavior was also studied with the molecular logic function of the AND gate. Furthermore, "Test Kits" coated with sensor 1 showed the successful selective detection of Al3+ ion under UV light.