Photochemical and photophysical properties of indoprofen

The photophysical properties and photochemistry of indoprofen (INP) have been investigated. Absorption and emission spectroscopies in phosphate buffer, ethanol and ether show that INP photophysics is dominated by a singlet-singlet transition of pipi* character. INP fluoresces at room temperature, with a quantum yield approximately 0.04. Flash photolysis experiments together with the lack of phosphorescence at room temperature point to a very weak intersystem crossing. The photoreactivity of INP is centered on the propionic acid chain and gives rise to photoproducts similar to those obtained with other arylpropionic acids (ethyl, hydroxyethyl and acetyl derivatives). Thus, irradiation of INP in aqueous buffer results in photodecarboxylation and leads mainly to oxidative compounds whose proportions increase with increasing oxygen concentration. These data suggest a photoreactivity occurring from the excited singlet state.