Synthesis and Purification of Novel Non-Aromatic Non-Cyclic Tetrapyrrolic Derivatives for Use in Photodynamic Therapy

• Liam Dress, Chemistry, University of Delaware

• Joel Rosenthal, Chemistry and Biochemistry, University of Delaware

Photodynamic therapy (PDT) is a cancer treatment option that ablates cancerous cells and tumors through photoinduced sensitization of singlet oxygen. We have developed a nontraditional, non-cyclic, non-aromatic tetrapyrrole ligand scaffold called a dimethylbiladiene (DMBil1), which can serve as an alternative to traditional photosensitizer complexes. Investigation into this structure has shown that substituting the functional groups has profound effects on the photochemical properties of the scaffold. These effects are further amplified through the insertion of a Pd(II) metal center in the scaffold, producing palladium biladiene (Pd[DMBil1]) which allows for increased levels of singlet oxygen sensitization when irradiated by visible light. In an effort to extend the absorption profile for Pd[DMBil1] further into the phototherapeutic window (650 – 850 nm) and increase the singlet oxygen quantum yield, synthetic modifications to the Pd[DMBil1] architecture were carried out. Specifically, a 6-membered carbon ring was substituted into the 10 position, in the place of the dimethyl groups, producing the precursors for 10-cyclohexanebiladiene (CHBil). The synthesis of this novel class of compounds is intended for the study of the effect of the cyclohexyl group on the overall scaffold’s photochemical properties, potentially allowing for its use as a phototherapeutic agent through absorption within the phototherapeutic window and increased singlet oxygen generation.