A reversible dual-channel chemosensor for fluoride anion

A colorimetric and fluorescent fluoride probe bearing phenolic hydroxy and imine groups has been designed and synthesised. This receptor could visually and spectroscopically recognise F⁻  with high selectivity over other anions. After the addition of fluoride ions to the solution of ([1,1′-biphenyl]-4,4′-diylbis (azanylylidene)) bis (methanylylidene)) bis (naphthalen-2-ol) (TY), since the deprotonation reaction occurred between the sensor and fluoride, the fluorescence intensity of the solution changed significantly. Furthermore, the quenched fluorescence caused by fluoride ions could be recovered upon the addition of calcium ions to this complex solution. This resulted in an ‘OFF-ON-OFF’ type sensing. In particular, an IMP logic gate has been proposed using the output obtained from the fluorescence studies. The fluorescence, UV-vis titration and ¹H NMR titration experiments indicated that the effects might occur via a combined process including hydrogen bond and deprotonation between the sensor and F⁻ .