A novel bifunctional fluorescent probe for selectively sensing Hg2+ or ClO− and its application in living cell imaging

A new triazole compound, 2H-1,2,3-triazole-4,5-dicarboxylate containing double ester groups was firstly synthesized by one-step reaction and further combined with rhodamine B to generate a novel "turn-on" fluorescent probe L2 characterized by 1H NMR, 13C NMR, and HRMS techniques, respectively. The structural properties, quantum chemical parameters, and physiochemical parameters of the compound L2 were investigated using the computational chemistry method. The probe L1 showed good selectivity and sensitivity to Hg2+ in DMF/Tris-HCl (1:1, v/v, pH = 6.0, 20 μM) solution and to ClO− in MeOH (20 μM) solution. The spectral sensing behaviors of L1 toward 19 kinds of metal ions and 14 kinds of anions were respectively determined by fluorescence spectra and UV absorption spectra. A new emission peak appeared at 585 nm in the presence of Hg2+ and 576 nm in the presence of ClO− respectively. Meanwhile, the fluorescence intensity enhanced significantly along with naked-eye sensitive color changes, which indicated that the spiro-ring moiety of rhodamine was converted to the open-ring state in the presence of Hg2+ and formed the new complex as 1:2 M ratios confirmed by using MS, Job's plot, 1H NMR titrations, and TD-DFT calculation. Moreover, the limits of detection (LOD) for Hg2+ and ClO− were calculated as 4.73 nM and 0.21 μM based on the 3σ/k method, respectively. In addition, the results of the biological activity assay revealed that L1 showed less low cytotoxicity to HeLa cells. Furthermore, the probe L2 was successfully used for bioimaging Hg2+ and ClO− in HeLa cells, thereby indicating its great potential for the micro-detection of Hg2+ and ClO− in vivo.