Sensing of diclofenac by a porphyrin-based artificial receptor

The reported studies deal with the synthesis of porphyrin chemosensor 2, designed for the detection of the emerging pollutant diclofenac. Owing to the peculiar structure of its molecular frame, which is composed of a tetrapyrrolic platform linked to a rhodamine B residue, receptor 2 reversibly interacts with diclofenac sodium salt (DCF)Na. The resulting 2@DCF adduct was detected by UV-Vis spectroscopy in a large pH range (5.5-9.0) as well as in the presence of competitive analytes. Both static and time-resolved fluorescence, resonance light scattering (RLS) and UV-Vis spectroscopies allowed for the evaluation of the binding behaviour, in terms of the association constant and structural features of the formed 2@DCF. In particular, the host-guest recognition event occurs with the growth of large porphyrin aggregates, as stated by the quenching of the fluorescence emission as well as the enhancement of RLS intensities, and with an overall 1 : 1 binding constant of about 105 M−1.