Turkish Journal of Chemistry




Two new azo-Schiff base receptors (L$_{{1}}$ and L$_{{2}})$ containing azo and azomethine groups with a conjugated group (benzyl ring of anthranilic acid, in L$_{{1}})$ and electron-donating group (alkyl chain of hexanoic acid, in L$_{{2}})$ were synthesized and characterized. Azo-hydrazone/phenol-keto tautomerism and solvatochromism were investigated. Studying their sensing ability towards cations (Co$^{2+}$, Cu$^{2+}$, Zn$^{2+}$, Ni$^{2+}$, Pb$^{2+}$, Cd$^{2+}$, Mn$^{2+}$, Fe$^{3+}$, Cr$^{3+}$, and Al$^{3+})$, high sensitivity and selectivity were recorded for Fe$^{3+}$ by naked eye and UV-Vis spectra in DMF-aqueous HEPES buffer (v:v, 1:1, pH 6.8). The color of L$_{{1}}$ and L$_{{2}})$ solutions instantly changed from yellow to deep orange and pale orange. L$_{{2}})$ sensed Cu$^{2+}$ and Al$^{3+}$ ions selectively by UV-Vis spectra. The interactions of receptors with F$^{-}$, Cl$^{-}$, CH$_{3}$COO$^{-}$, C$_{2}$O$_{4}^{2-}$, H$_{2}$PO$_{4}^{-}$, and OH$^{-}$ anions were also investigated in DMF-HEPES 1:1 and 4:1 solvent mixtures. L$_{{1}})$ sensitively responded to anions according the order of OH$^{-}$ > C$_{2}$O$_{4}^{2-}$ > F$^{-}$ in the 1:1 mixture and OH$^{-}$ > F$^{-}$ > CH$_{3}$COO$^{-}$ > C$_{2}$O$_{4}^{2-}$ in the 4:1 mixture in UV-Vis spectra with color changing from pale yellow to dark yellow. However, L$_{{2}})$ showed weak spectral changes in the UV-Vis spectra, so its sensitivity was poorer than L$_{{1}})$, attributed to the effect of alkyl chains.


Azo-Schiff bases, tautomerism, cation sensing, anion sensing, Fe$^{3+}$/Cu$^{2+}$/Al$^{3+}$ sensors, F$^{-}$/CH$_{3}$COO$^{-}$/ C$_{2}$O$_{4}^{2-}$ sensors

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