Hexaphenylbenzene-based fluorescent probes for the detection of fluoride ions

Abstract

Novel hexaphenylbenzene derivatives (HPB-1 and HPB-2) were synthesized and their structural and optical properties were characterized using ¹H NMR, ¹³C NMR, HRMS, absorption and fluorescence spectroscopies. The effect of various anions (AcO⁻, NO₃⁻, HSO₄⁻, ClO⁻, ClO₄⁻, SCN⁻, CN⁻, F⁻, Cl⁻, Br⁻, I⁻ and H₂PO₄⁻) on the optical properties of these new compounds was investigated in THF. Among the different anions, significant changes in the fluorescence spectra of HPB-1 and HPB-2 were observed in the presence of only F⁻ ions. The interaction ratios of HPB-1 and HPB-2 with F⁻ ions were determined to be 1 : 1 and the binding constants (K_A) were found to be 0.0417 M⁻¹ and 0.982 M⁻¹ for HPB-1 and HPB-2, respectively. The LOD values were calculated as 2.79 μM and 1.04 μM for HPB-1 and HPB-2, respectively. The mechanism of F⁻-ion sensing was investigated via¹H NMR titration. The obtained results show that the newly synthesized HPB-1 and HPB-2 compounds can be a turn-on fluorometric sensor with high selectivity for F⁻ ions.