Ir(III) Complexes for Photodynamic Therapy

Ir(III) Complexes for Photodynamic Therapy

Author: Chemistry – A European Journal

Photodynamic therapy (PDT) is a chemotherapeutic protocol against cancer. It acts selectively in cancerous tissues after local activation with light. Upon light excitation, a photosensitizer (PS) initiates a photochemical reaction that produces biologically active species at cytotoxic levels.

Gustavo Espino, Begoña Garcí­a, Universidad de Burgos, Spain, and colleagues have prepared neutral biscyclometalated Ir(III) complexes (pictured) as potential PS agents against colon cancer. The complexes have the general formula [Ir(C^N)2(N^O)], where the N^O ligands are 2‐(benzimidazolyl)phenolate‐N,O or 2‐(benzothiazolyl)phenolate‐N,O, and the C^N ligands are 2‐(phenyl)pyridinate derivatives. The compounds are phosphorescent, generate singlet oxygen (1O2) photocatalytically, and accumulate in cancer cells.

The team identified the complex of formula [Ir(dfppy)2(L)] (dfppy = 2‐(4,6‐difluorophenyl)pyridinate, L = 2‐(benzimidazolyl)phenolate‐N,O) as a potential agent for PDT. This complex combines excellent photophysical properties, internalization in cancer cells, and a good ability for 1O2 production. It shows an eightfold rise in cytotoxic activity upon blue-light irradiation versus in the dark. The team found that the photophysical and electrochemical properties of the described complexes depend preeminently on the N^O ligand. More studies are necessary to better understand the strong effects on the anticancer properties derived from the subtle structural change in the O^N ligand.


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