Synthesis and characterization of new fluorene-based singlet oxygen sensitizers

The synthesis, photophysical characterization, and determination of singlet oxygen quantum yields (Phi(Delta)) for a class of fluorene derivatives with potential application in two-photon photodynamic therapy (PDT) is reported. It has been demonstrated that these compounds possess the ability to generate singlet oxygen (O-1(2)) upon excitation. A photochemical method, using 1,3-diphenylisobenzofuran (DPBF) as O-1(2) chemical quencher, was employed to determine the singlet oxygen quantum yields (Phi(Delta)) of the fluorene- based photosensitizers in ethanol. Phi(Delta) values ranged from 0.35 to 0.75. These derivatives may have potential application as two-photon photosensitizers when pumped via two-photon excitation in the near-IR spectral region.