Naphthoxazole-Based Singlet Oxygen Fluorescent Probes

In this study, we report the synthesis and photochemical behavior of a new family of photoactive compounds to assess its potential as singlet oxygen (O-1(2)) probes. The candidate dyads are composed by a O-1(2) trap plus a naphthoxazole moiety linked directly or through an unsaturated bond to the oxazole ring. In the native state, the inherent great fluorescence of the naphthoxazole moiety is quenched; but in the presence of O-1(2), generated by the addition and appropriate irradiation of an external photosensitizer, a photooxidation reaction occurs leading to the formation of a new chemical entity whose fluorescence is two orders of magnitude higher than that of the initial compound, at the optimal selected wavelength. The presented dyads outperform the commonly used indirect fluorescent O-1(2) probes in terms of fluorescence enhancement maintaining the required specificity for O-1(2) detection in solution.