A Probe for Multi Detection of Al3+, Zn2+ and Cd2+ Ions via Turn-On Fluorescence Responses

The hydrazide (LH) using 6-(hydroxymethyl)picolinohydrazide and 2-hydroxynapthaldehyde was synthesized and characterized. This acts as a TURN-ON fluorescence sensor for Al3+, Zn2+ and Cd2+ ions by giving different emission maxima. The LH itself is weakly emissive having the maximum at 495 nm. Gradual addition of chloride salts of Al3+, Zn2+ and Cd2+ ions to LH, gave rise to emission peaks at 485, 570 and 540 nm, in MeOH-HEPES buffer solution (5 mM, pH = 7.3, 7:3, v/v). Addition of AP+, Zn2+ and Cd2+ ions to a solution of LH generate new absorbance and fluorescencepeaks due to binding of r with Al3+ ion in 2:1 ratio; Zn2+ and Cd2+ ions in 1:1 ratios. Fluorescence reversibility was also studied by adding Al3+., Zn2+ and Cd2+ ions with Na(2)EDTA. Calculated detection limits of LH towards Al3+, Zn2+ and Cd2+ ions are 5.7 x10(-9),1.09 x 10(-6) and 1.64 x 10(-6)M repectively. Based on experimental and theoretical results the formulae [Al(L)(2)](+), lZh(L)Cl(H2O)(2)] and [Cd(L)Cl(H2O)(2)] were assigned and these complexes generated in situ are useful fluorophore to detect fluoride and dihydrogen phosphate ions, which act by quenching the fluorescence responses. The results of DFT/TDDFT calculations on LH, [Al(L)(2)](+), [Zn(L)Cl(H2O)(2)] and [Cd (L)Cl(H2O)(2)] were consistent with the experimental results. (C) 2017 Elsevier B.V. All rights reserved.