Dirhodium partial paddlewheel complexes featuring electron donating bridging ligands and electron accepting chelating diimine ligands have been shown to act as excellent PDT agents due their ability to bind and photocleave DNA, as well as to generate 1O2 upon irradiation. The bridging ligands p-chlorobenzylformamidinate, p-bromobenzylformamidinate, and p-iodobenzylformamidinate were used in the synthesis of two new series of dirhodium complexes, building upon the previous work in the Dunbar Group with the p-fluoroformamidinate ligand. Through the heavy atom effect, these substituted formamidinate ligands may facilitate an increase in the population of the long-lived triplet excited state of the dirhodium complex, which is important for improving efficiency of the complex as a photosensitizer. Diimine ligands were used in conjunction with the above bridging ligands to yield complexes of the type [Rh2(X-Form)2(NN)2](BF4)2. These complexes were studied for their in vitro photocytotoxicity, and show excellent promise as PDT agents due to their high photocytotoxicity index and good absorption in the visible region. DNA photocleavage experiments and Resazurin cell viability assays were performed, showing great difference in LC50 irradiated versus LC50 values in the dark. Cell microscopy studies with HeLa cells were also performed to elucidate the mechanism of action of these dirhodium complexes. This systematic investigation of the effect of halogen substitution on the photophysical properties and photocytotoxicity of these dirhodium complexes will be presented and discussed.

Photocytotoxicity of dirhodium (II,II) complexes featuring formamidinate bridging ligands with halogen substitution

2019 Fall National Meeting

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