A quinoline-based Cu²⁺ ion complex fluorescence probe for selective detection of inorganic phosphate anion in aqueous...

A quinaldine functionalized probe QP has been designed and synthesized. It exhibited selective turn-off fluorescence response toward Cu²⁺ ion over most of the biologically important ions at physiological pH. The binding ratio of the probe QP and Cu²⁺ ion was determined to be 1:1 through fluorescence titration, Job's plot and ESI-MS. The binding constant (K) of Cu²⁺ to probe QP was found to be 2.12×10⁴M^-1. Further, the Cu²⁺ ensemble of probe QP was found to respond H₂PO₄^- and HPO₄^2- among other important biological anions via fluorescence turn-on response at physiological pH. Fluorescence microscopy imaging using living Hela cells showed that probe QP could be used as an effective fluorescent probe for detecting Cu²⁺ cation and H₂PO₄^- and HPO₄^2- anions in living cells.