Attaching electron donating groups on the meso-phenyl and meso-naphthyl make aryl substituted BODIPYs act as good photosensitizer for singlet oxygen formation

meso-phenyl and meso-naphthyl substituted BODIPY derivatives were synthesized as singlet oxygen photosensitizers. Strengthening the electron donating ability of the phenyl or naphthyl by attaching OCH3 or OH group makes these BODIPYs efficiently generate singlet oxygen in polar solvents accompanied by strong fluorescence quenching. The BODIPYs exhibited higher fluorescence quantum yields in non polar solvents, but became much less emissive in polar solvents. The results are explained by the involvement of photoinduced electron or charge transfer process in the lowest lying excited singlet state (S1). These results indicate that these BODIPY dyes can be potential singlet oxygen photosensitizers for the application in PDT and theranostics.