Dual functioning thieno-pyrrole fused BODIPY dyes for NIR optical imaging and photodynamic therapy: Singlet oxygen generation without heavy halogen atom assistance

We discovered a rare phenomenon wherein a thieno-pyrrole fused BODIPY dye (SBDPiR690) generates singlet oxygen without heavy halogen atom substituents. SBDPiR690 generates both singlet oxygen and fluorescence. To our knowledge, this is the first example of such a finding. To establish a structure-photophysical property relationship, we prepared SBDPiR analogs with electron-withdrawing groups at the para-position of the phenyl groups. The electron-withdrawing groups increased the HOMO-LUMO energy gap and singlet oxygen generation. Among the analogs, SBDPiR688, a CF₃ analog, had an excellent dual functionality of brightness (82290-m^-1-cm^-1) and phototoxic power (99170-m^-1-cm^-1) comparable to those of Pc 4, due to a high extinction coefficient (211-000-m^-1-cm^-1) and balanced decay (Φ_flu=0.39 and Φ_Δ=0.47). The dual functionality of the lead compound SBDPiR690 was successfully applied to preclinical optical imaging and for PDT to effectively control a subcutaneous tumor. Being in a relationship: We discovered and identified key structure-photophysical property relationships within BODIPY dyes that produce singlet oxygen without heavy halogen atom assistance. The exclusion of heavy atoms increases their brightness, which we successfully translated in vivo. We also demonstrate the phototoxic power through optical-guided photodynamic therapy.