Novel “turn-off” and “turn-on” fluorescent responses for Zr4+ enabled by rare-earth coordination polymers based on the 2,5-dihydroxyterephthalic acid ligand

Abstract

Two novel isostructural coordination polymers, [[Tb₂(H₂dhtp)₃(DMF)₂(H₂O)₄]·2DMF·H₂O]_n (1) and [[Y₂(H₂dhtp)₃(DMF)₂(H₂O)₄]·2DMF·H₂O]_n (2) (H₄dhtp = 2,5-dihydroxyterephthalic acid), were synthesized via solvent evaporation and thoroughly characterized. Fluorescence studies revealed that both compounds exhibit significant quenching upon exposure to Fe³⁺. Notably, they exhibit a unique and concentration-dependent dual-response to Zr⁴⁺ ions, characterized by distinct fluorescence turn-off (0–100 μM for 1; 0–90 μM for 2) and turn-on (100–700 μM for 1; 90–500 μM for 2) regions. To our knowledge, these materials represent the first example of Zr⁴⁺-sensing probes based on Tb³⁺/Y³⁺ coordination complexes with the H₄dhtp ligand, showcasing significant potential for the design of novel switchable sensors.