Computational study on fluoride recognition by an urea-activated phthalimide chemosensor

The mechanism of the fluoride anion recognition by an urea–phthalimide chemosensor has been studied in detail by means of CASPT2//CASSCF calculations. Computational data are in well-agreement with changes in the photophysical properties previously reported experimentally in the presence or absence of fluoride anion. In both cases, fast relaxation from the S2 potential energy surface leads to S1 population. Deactivation of the excited state is in agreement with the experimental change in fluorescence observed when the anion is present. Mechanistic information obtained allows to provide an explanation of the experimental data and to suggest some modifications to improve the synthetic applicability of this type of chemosensors.