Construction of a new three-dimensional fluorescent probe based on BaII ions and 2,5-bis-(4-carboxy-phenylsulfanyl)-terephthalic acid

Highlights: • A Ba-based framework of [Ba(PSTP)_0.5(H₂O)]_n (1) with excellent chemical stability was assembled. • It emits blue light (λ_em = 440 nm) when it is excitated at 360 nm. • The water solvent, acting as the luminescence quencher, leading to the fluorescence intensity of 1 greatly decrease. • Complex 1 can be used as a good fluorescent probe to detect TNP and 4-NA with high selectivity and sensitivity. -- Abstract: A new barium(II)-based coordination polymer, poly[half[μ₇-2,5-bis-(4-carboxy-phenylsulfanyl)-terephthalic acid-κ⁷O¹:O²:O^3#3:O^4#1:O^4#4:O^5#2:O^5#4]barium(II)], [Ba(PSTP)_0.5(H₂O)]_n (1), was synthesized through a simple solvothermal method using Ba^II ions and 2,5-bis-(4-carboxy-phenylsulfanyl)-terephthalic acid (H₄PSTP). The asymmetric unit includes one Ba^II center, half of PSTP⁴⁻ ligand and one coordinated water molecule. Thermal stability, IR spectroscopy, el. emental analysis, powder X-ray diffraction, solid-state photoluminescence, and the ability to detect small organic molecules as a fluorescent probe were investigated. Experimental results indicate that 2,4,6-trinitrophenol (TNP) and p-nitroaniline (4-NA) have a strong quenching effect on the fluorescence of 1 (dispersed in DMF solution), and the quenching rate is as high as 99.7% and 99.2%, respectively. The quenching constant K_sv is 9.6 × 10⁵ M⁻¹ and 5.4 × 10⁵ M⁻¹, respectively. The calculated LOD (limit of detection) values are 0.56 ppm (for 4-NA) and 0.31 ppm (for TNP), respectively. It can be used as a good fluorescent probe to detect TNP and 4-NA effectively with high selectivity and high sensitivity.