A guanidine based bis Schiff base chemosensor for colorimetric detection of Hg(II) and fluorescent detection of Zn(II) ions

A novel guanidine base colorimetric and fluorescent bis Schiff base chemosensor L has been designed synthesized and characterized by elemental analyses,H-1 NMR, FT-IR and ESI-MS spectral analysis. The chemosensor L could detect Hg2+ by "naked eye" colour change from yellow to red and Zn2+ through selective fluorescence enhancement in CH3OH-tris buffer (1/1, v/v) over other metal ions commonly obtained in physiological and environmental samples. The Job's plot analysis revealed that 1:2 and 1:1 coordination patterns for L-Hg2+ and LZn2+ complexes respectively, which have further been confirmed by ESI-MS spectra. The DFT calculations are also in agreement with the experimental results. The limit of detection for Hg2+ and Zn2+ are found to be 9.89 x 10(-7) M and 1.23 x 10(-6) M respectively, which are far below than the guidelines provided by World Health Organization (WHO) for drinking water. Moreover the chemosensor L has applications in real sample analysis in environmental and biological samples and building molecular logical devices. To the best of our knowledge, this observation is the first case where a guanidine base bis Schiff base is being utilized for sensing of metal ions.