The two isomers of a cyclometallated palladium sensitizer show different photodynamic properties in cancer cells.

This report demonstrates that changing the position of the carbon-metal bond in a polypyridyl cyclopalladated complex, i.e. going from PdL1 (N<^>N<^>C<^>N) to PdL2 (N<^>N<^>N<^>C), dramatically influences the photodynamic properties of the complex in cancer cells. This effect is primarily attributed to the significantly difference in absorbance and singlet oxygen quantum yields between the two isomers.