Dual mode selective chemosensor for copper and fluoride ions: a fluorometric, colorimetric and theoretical investigation

A pyrene containing chemosensor viz. 1 has been designed for the efficient and selective detection of Cu2+ and F(-)ions in dual sensing mode which do not interfere with each other. The chemosensing behavior of 1 towards Cu2+ was demonstrated through fluorescence, time resolved fluorescence spectroscopy, and visual fluorescence colour changes, and towards F-through naked-eye colour changes, absorption and H-1 NMR titrations. The chemosensor 1 shows excellent selectivity towards Cu2+ through an excimer switch-off mechanism. Density Functional Theory (DFT) calculations were performed to show the structure and electronic properties of 1 and its copper complex [1-Cu2+]. The selectivity and sensitivity towards F-were explained in terms of H-bonding interactions between 1 and F-, then deprotonation of 1. The biological application of 1 has been evaluated in HEK 293 cells and it exhibits good membrane permeability for the detection of Cu2+. The sensor also shows appreciable sensitivity towards fluoride in toothpaste.