Isoquinoline-Fused Benzimidazoles Based Highly Selective Fluorogenic Receptors for Detection of Cu, Fe, and Cl Ions: Cytotoxicity and HepG2 Cancer Cell Imaging.

An efficient isoquinoline-fused benzimidazole-based "turn-on" fluorescence receptor 9,10-bis(2-phenylhydrazineyl)-7H-benzo[de]imidazo[2,1-a]isoquinolin-7-one OXPH(ANQ) and "turn-off" fluorescence receptor 9,10-bis((3-(1H-imidazol-1-yl)propyl)amino)-7H-benzo[de]imidazo[2,1-a]isoquinolin-7-one OXPID(ANQ) were prepared and characterized by various spectral techniques. The sensing behavior of receptors was demonstrated by UV-vis and fluorescence experiments, and naked-eye detection exhibited prominent visual emission color change toward Cu/Cl and Fe over other testing cations/anions in DMSO:water (9:1, ν/v) solution. The 1:1 binding stoichiometry was confirmed by Job's plot, FT-IR, mass spectral titration, and also DFT studies with target ions as evidence for the binding nature of OXPH(ANQ)/OXPID(ANQ) with Cu/Cl and Fe ions, respectively.