Abstract:

A fluorescent chemosensor, N′-((2-hydroxynaphthalen-1-yl)methylene)-2-naphthohydrazone(3), was designed and synthesized. Compound 3 was confirmed by IR, 1H NMR and ESI-MS. Compound 3 was investigated to recognize transition metal ions such as Zn²⁺, Cd²⁺, Cu2+, Hg²⁺, Pb²⁺ and Ni²⁺ via the fluorescence spectroscopic method. Mechanism of enhancement of the fluorescence of compound ]3 by Zn²⁺ was briefly discussed. The experiments show that acceptor 3 has a good selectivity of Zn²⁺ in acetonitrile. A new peak in the absorption spectrum of acceptor 3 at 435 nm appears for the addition of Zn²⁺ with the gradually increasing absorbancy, while five clear absorption points can be observed at 239, 302, 330, 342 and 387 nm, respectively. The fluorescence of acceptor 3 shows a highly selective response to Zn2+only. In acetonitrile Zn²⁺ induced a dramatic enhancement in the fluorescence of acceptor 3 by 101 folds at 516 nm, whereas the other transition metal ions had little influence on the fluorescence of acceptor 3. Job′s test showed acceptor 3 coordinated to Zn²⁺ to form a 1∶1 model complex.

Key words: naphthoylhydrazone, Zn²⁺, fluorescence enhancement, molecular recognition