Photodynamic therapy (PDT) is a non-invasive, pharmaceutical method utilizing light-activated reactions between a photosensitizer and molecular oxygen (3O2). Its medicinal use is based on the generation of cytotoxic singlet oxygen (ROS) and its ability to manage drug activity at a targeted area. Iridium (III) complexes are of increasing interest due to their desirable photophysical properties and stability; thus, they can be applied for use as photosensitizers. Ideally for photodynamic therapy, a red-shifted, and thus more easily penetrating complex with longer excited-state lifetimes and large quantum yields is desired. Such photophysical properties of iridium (III) complexes can be enhanced depending on which cyclometallating and dative ligands are incorporated. The way in which the complex is delivered for site-specific targeting must also be considered. Using a microwave-assisted approach, we have synthesized a water-soluble novel iridium complex with 2-phenylpyridine as the cyclometallating ligand and 4 4'-dicarboxy-2 2'-bipyridine acting as the dative ligand. The functional groups of the dative ligand serve as a means to tether the complex to a peptide. We will discuss how the use of microwave synthesis addresses several issues of chemical sustainability present in more traditional methods and promotes the twelve principles of green chemistry. In using a one-pot microwave method, we have successfully eliminated intermediate steps, lowered energy input, minimized the production of waste, and altogether avoided the use of hazardous synthesis techniques. We have also investigated the efficiency of the zwitterionic iridium (III) compound to act as a PDT agent through photophysical analysis and explored the pKas for the ground and excited states.

Green synthesis of heteroleptic iridium (III) complex for applications in photodynamic therapy

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.