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, 1H-,13 C-NMR and molecular mass. F3 exhibits a high selectivity for detection of Cr3+and Al3+ionsas 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 (Ka) for Cr3+and Al3+ were calculated and found to be 8.33 × 104M-1and 5.44 × 104M-1 , respectively. The detection limits were also calculated for Cr3+and Al 3+and found to be 2.5 × 10-7mol/L and 3.1 × 10-7mol/L, respectively.
