Design and synthesis of a hydrazinopthalazine derived chemosensor to detect metal ions Zn²⁺, Al³⁺ via CHEF effect with biological study and theoretical calculation

A multiple metal ion detector, H3L [H3L 1/4 4-methyl-2,6-bis((E)-(2-(phthalazin-1-yl)hydrazono)methyl)phenol] has been synthesized upon mixing 2,6-diformyl-4-methylphenol (DFP) and hydrochloride salt of hydrazinopthalazine in 1:2 ratio. H3L successfully detects Zn2+ and Al3+ ions through fluorescence enhancement in HEPES buffer (1:9, MeOH:H2O, v/v, pH 7.4). The fluorescent probe and its metal-bound compounds (1 and 2) are characterized using different spectroscopy and mass spectrometric techniques. The turn-on fluorescence response towards Zn2+ and Al3+ was explained based on PET-OFF, and chelation enhanced fluorescence (CHEF) ON processes. The binding mode and sensing mechanism of compounds 1 and 2 were confirmed using DFT calculations. H3L exhibits low detection limits and strong binding constants towards Zn2+ (2.37 x 10-6 M and 3.49 x 104 M-1) and Al3+ (1.32 x 10-6 M and 2.67 x 104 M-1) ions. It is successfully used in paper strips for the detection of Zn2+ and Al3+. Biocompatible H3L also applied as a visual probe for the practical determination of Zn2+ and Al3+ on cervical cancer cells.