A cell-compatible red light-emitting multianalyte chemosensor via three birds, one stone strategy

The design and synthesis of red light-emitting multianalyte chemosensors have always been a challenging task because of its specific requirement of coordination pocket and selective fluorescence mechanism. Herein, we develop a chemosensor via “three birds, one stone” strategy in which we can detect three metal ions with one ligand. A highly sensitive new azo functionalized rhodamine based luminescent sensor is synthesized for selective fluorogenic recognition of Al³⁺, Cr³⁺, and chromogenic recognition of Cu²⁺ in ethanol: H₂O medium in the red light-emitting zone. Among the guest metals, Cu²⁺ efficiently quenches the emission whereas Al³⁺ and Cr³⁺ induce increased luminescent 4.76 fold for Al³⁺ and 2.47 fold for Cr³⁺ through chelation-enhanced fluorescence (CHEF) and photo-induced electron transfer (PET) regulated mechanism with the formation of 1:1 complex. The restricted imine isomerization through complex formation inhibits ongoing PET process with the instantaneous onset of CHEF. The mechanism is in good consonance with NMR (¹H & ¹³C), FT-IR, elemental analysis, DFT, TCSPC, and pH-dependent studies. Micromolar range detection of 1.1 μM, 1.3 μM, and 1.5 μM for Cu²⁺, Al³⁺, and Cr³⁺ respectively, easy penetration into HLCs cells and higher imaging resolution increase its potentiality to assess Al³⁺ and Cr³⁺ in vitro. Moreover, paper strip application increases its viability as an onsite naked-eye portable solid probe.