Highly selective and sensitive colorimetric probe for Al3+ and Fe3+ metal ions based on 2-aminoquinolin-3-yl phenyl hydrazone Schiff base

Abstract A novel colorimetric probe based on 2-aminoquinolin-3-yl phenyl hydrazone Schiff base ligand (SBL) derivatives for the detection of metal ions viz. Al 3+ and Fe 3+ in ethanol solution was designed and synthesized. The SBL displayed quick response to Al 3+ with red shift of 34 nm at 427 nm in visible region and at 420 nm for Fe 3+ over the other metal ions. SBL when titrated with Fe 3+ from 0 to 100 equivalent, at 233 nm and 402 nm isosbestic points are observed with increasing concentration of Fe 3+ with binding constant 3.81 × 10 5  M −1 . This clearly shows the affinity of SBL towards Fe 3+ . Similar titration was carried out for Al 3+ and binding constant value was found to be 8.15 × 10 5  M −1 by Benesi Hildebrand method. Moreover, electrochemical studies by using cyclic voltammetry were also performed to know the reversibility of complex. SBL-Fe 3+ was found to be reversible after addition of EDTA, thus SBL can be effectively used as switch chemosensor for detection of Fe 3+ . Job’s plot method shows 1:1 stoichiometry for SBL-Al 3+ complex and 2:1 for SBL-Fe 3+ complex. In addition, 1 H NMR titration experiments of SBL with Al 3+ confirms the binding mechanism as 1:1 host guest complex.