A new fluorene-based Schiff-base as fluorescent chemosensor for selective detection of Cr3+ and Al3+

2-((9H-fluoren-2-ylimino) methyl)phenol (F3) was synthesized by condensation reaction of 9H-fluoren-2-amine and 2-hydroxybenzaldehyde in EtOH and characterized by its melting point, H-1-, C-13 NMR and molecular mass. F3 exhibits a high selectivity for detection of Cr3+ and Al3+ ions as a fluorescent chemosensor and showed a single emission band at 536 nm upon excitation at 333 nm according to fluorescence emission studies. The addition of Cr3+ and Al3+ make a significant increase in fluorescent intensity at 536 nm in CH3CN, while other metal ions have almost no influence on the fluorescence. The fluorescence enhancement was attributed to the inhibited C=N isomerization and the obstructed excited state intra-molecular proton transfer (ESIPT) of compound F3. Job's plot and DFT calculations data showed that the binding stoichiometries of F3 with Cr3+ and Al3+ are 2:1. The association constants (K-a) for Cr3+ and Al3+ were calculated and found to be 8.33 x 10(4) M-1 and 5.44 x 10(4) M-1, respectively. The detection limits were also calculated for Cr3+ and Al3+ and found to be 2.5 x 10(-7) mol/L and 3.1 x 10(-7) mol/L, respectively. (C) 2017 Published by Elsevier B.V.