Synthesis of Extended Isocorroles as a Photosensitizer for Photodynamic Therapy

• Elizabeth Bodio, Chemistry, University of Delaware

• Joel Rosenthal, Chemistry and Biochemistry, University of Delaware

Photodynamic Therapy (PDT) is an alternative cancer treatment that utilizes a photosensitizer to target tumor cells by generating highly reactive singlet oxygen upon irradiation with light, effectively eradicating nearby cancer cells. To enhance the efficacy of PDT, an ideal photosensitizer should yield a high amount of singlet oxygen and strongly absorb light within the phototherapeutic region (between 650 to 900 nm), however current commercial photosensitizers do not absorb strongly within the phototherapeutic region. The Rosenthal Lab has synthesized a nontraditional tetrapyrrole, titled the 10,10-dimethylbiladiene (DMBil), which has been metalated with palladium to generate Pd[DMBil]. Pd[DMBil] has shown efficient production of singlet oxygen, but lacks strong absorbance bands within the phototherapeutic region. Ring closure of the biladiene to the isocorrole using an iodine(III) reagent successfully red-shifted the absorbance profile to approximately 850 nm. To further redshift the absorbance, the isocorrole conjugation has been extended via introduction of vinyl groups. Addition of vinyl groups will provide handles for Heck couplings, which should push the absorbance further into the red region, making the extended isocorroles a good candidate for PDT applications.