A Novel Naphthylidene-diimine Chemosensor for Selective Colorimetric and Fluorometric Detection of Al 3+ and CN - Ions.

A naphthylidene-diimine L 2 was newly designed, and its structure was identified by elemental analysis and spectroscopic methods. The effect of temperature, acid-base and light on enol-keto tautomerism in this Schiff base was evaluated by colorimetry, UV-Vis and fluorescence spectroscopy. Under irradiation 365 nm, L 2 emitted yellow, orange and strong green emission in pure, basic and aqueous DMSO media (v/v, 1/1), respectively. Its ionochromic behavior against various cations (Fe 3+ , Al 3+ , Cr 3+ , Cu 2+ , Co 2+ , Ni 2+ , Zn 2+ , Cd 2+ , Pb 2+ , Ba 2+ and Ag + ) and anions (F - , Cl - , CH 3 COO - , SO 3 2- , S 2 O 3 2- , HSO 4 - , H 2 PO 4 - , NO 3 - , CN - , and OH - ) was investigated in aqueous DMSO media (v/v, 1/1) by UV-Vis and fluorescence experiments. Dark yellow color of L 2 changed to colorless for Fe 3+ , Cr 3+ and HSO 4 - ions, and turned to light yellow for Al 3+ and Cu 2+ ions, and to orange for CN - and OH - ions. According to UV-Vis data, the chemosensor displayed selective recognition towards Fe 3+ , Al 3+ , Cu 2+ , HSO 4 - , CN - and OH - with a 1:1 stoichiometric ratio. At the excitation wavelength of 365 nm, L 2 gave strong yellowish white emission (λ em = 445 and 539 nm) in the presence of Al 3+ , and the intensity increased about 12.5 times. On the other hand, the chemosensor displayed one emission band at 452 nm and 450 nm in the presence of CN - and OH - with 1.9 fold and 2.3 fold fluorescence enhancement, respectively.