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=Zn2+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 1.1×10−10 M, 1.01×10−8 M and 3.18×10−10 M and further LOQ (limit of quantification) as 0.37×10−9 M, 0.33×10−7 M and 5.26×10−9 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. A new stable tripodal terpyridine is demonstrated as a ‘ratiometric’ dual fluorescence probe for sensitive and selective detection and determination of zinc and thorium ions in aqueous solutions. The F‐ ion is quantitatively determined by decreasing the fluorescence intensity of the tripodal terpyridine‐zinc(II) complex.