Ferrocenyl-based unsymmetrical azines as multisignaling sensors for Hg2+, Cu2+ in aqueous environment

Abstract Seven ferrocenyl-based unsymmetrical azines 3a – 3f and 5a were synthesized under metal-free conditions in good yields. Ferrocene-based unsymmetrical azines 3f and 5a have shown to be excellent multichannel chemosensors for Hg 2+ and Cu 2+ ions in aqueous environment. The color of the solution containing chemosensor 3f changed from yellow to colorless, upon the addition of Hg 2+ and Cu 2+ ions. Quantification of the absorption titration analysis shows that the detection limit was 6.77 × 10 −7  M for 3f -Cu 2+ and 7.19 × 10 −7  M for 3f -Hg 2+ , respectively. For 5a , the detection limit can reach 1.29 × 10 −7  M and 2.40 × 10 −7  M for Cu 2+ and Hg 2+ , respectively. Moreover, 1-substituted ferrocene-based unsymmetrical azines 3a–3e with electron-rich, electron-neutral, and electron-deficient aryl groups have significant influence on the sensitivity.