Ruthenium(II) Complex-based Highly Specific Luminescence Light-up Probe for Detecting HOCl via C(sp2)-H Chlorination

A bis-heteroleptic Ru(II) complex, 1[PF6](2) of a benzimidazole substituted pyridyl-1,2,3-triazole ligand (BiPT) for highly selective luminescence turn-on detection of hypochlorous acid (HOCl) is reported. Detection of HOCl is achieved by the Markovnikov addition of HOCl to the C=C bond of 1,2,3-triazole and a successive highly specific C(sp(2))-H chlorination at the C5 position of 1,2,3-triazole. The chlorination at C5 in 1,2,3-triazole is supported by high-resolution mass spectrometry and H-1 NMR study. 1[PF6](2) shows high sensitivity towards HOCl in PBS buffer (pH 7.4) containing 5 % acetonitrile with a 37-fold luminescence light-up and a detection limit as low as 7.5 mu M. HOCl mediated C(sp(2))-H chlorination increases the (MC)-M-3-(MLCT)-M-3 energy gap as well as the population of the (MLCT)-M-3 excited state and exhibits the radiative decay from the excited state of 1. The probe showed low cytotoxicity and efficiently permeated the cell membrane. The cell-imaging experiments revealed rapid staining of the HeLa cells in the presence of exogenous HOCl.

Automated summary

A bis-heteroleptic Ru(II) complex, 1[PF6](2), with a benzimidazole substituted pyridyl-1,2,3-triazole ligand (BiPT) is utilized for the highly selective luminescence turn-on detection of hypochlorous acid (HOCl). The detection of HOCl is achieved through Markovnikov addition and specific C(sp(2))-H chlorination reactions. The Ru(II) complex shows high sensitivity and low cytotoxicity, allowing for efficient cell imaging in the presence of exogenous HOCl.