New Tritopic Terpyridine-based Fluorescent Probe for the Efficient Determination of Th⁴⁺, Zn²⁺ and F^- Ions

The present work demonstrates the determination of thorium (Th4+), zinc (Zn2+) and fluoride (F-) ions by employing a substituted tripodal terpyridine (TP) as a fluorescence sensor. The distinct fluorescence intensities of the free TP and TP-M complexes (M=Zn(2+)or Th4+) with the same emission wavelength at 468 nm were observed in steady-state photoluminescence (PL) spectra at pH 7.0 with a 1 : 3 ratio of metal to the ligand. A ratiometric dual fluorescence signals for Zn2+ and Th4+ were displayed by the probe TP at varied concentrations. Furthermore, the quantitative determination of F- ions was achieved through the addition of F- to the tripod-terpyridine-zinc complex (TP-Zn2+) where the fluorescence intensity decreases gradually. Notably, the present work facilitates the LOD (limit of detection) as 1.1x10(-10) M, 1.01x10(-8) M and 3.18x10(-10) M and further LOQ (limit of quantification) as 0.37x10(-9) M, 0.33x10(-7) M and 5.26x10(-9) M for Zn2+, Th4+ and F- ions, respectively. The predicted absorption spectra of TP show HOMO to LUMO+2 electronic excitation at 358 nm whereas the complex TP-Th4+ exhibits HOMO to LUMO+1 electronic excitation at 568 nm.