A benzimidazole-based chemodosimeter for the fluorometric detection of Zn and Cu via 1,5 proton shifts and C-N bond cleavage.

Here, we report the design and synthesis of the fluorescent probe APBHN, which was derived from 2-(1H-benzo[d]imidazol-2-yl)benzenamine and is capable of detecting intracellular Zn and Cu ions in the micromolar range. Single-crystal X-ray analysis revealed that the structure of the ligand comprises a fused cyclic system with a pendent naphthol moiety. With the addition of Zn and Cu ions the inherent fluorescence behaviour of the ligand APBHN is perturbed via a chemodosimetric change that involves a 1,5 proton shift followed by C-N bond cleavage. Upon detailed analysis, it was found that the ligand forms 1 : 1 and 1 : 2 (metal to ligand) complexes with the corresponding metal ions. The detection limits of Zn2+ and Cu2+ were 5.59 μM and 0.148 μM, respectively, with APBHN, which are lower than the WHO guidelines (76 μM for Zn2+ and 31.5 μM for Cu2+) for drinking water. Moreover, APBHN could be used as a practical, visible colorimetric test kit for both Zn2+ and Cu2+. APBHN can efficiently detect Zn2+ and Cu2+ in liver carcinoma cells with insignificant cytotoxicity.