Tuning the Organelle-Specific Imaging and Photodynamic Therapeutic Efficacy of Theranostic Mono- and Trinuclear Organometallic Iridium(III) Complexes

The organelle-specific localization of mononuclear and
trinuclear
iridium(III) complexes and their photodynamic behavior within the
cells are described herein, emphasizing their structure–activity
relationship. Both the IrA2 and IrB2 complexes possess a pair of phenyl-benzothiazole
derived from the −CHO moieties of mononuclear organometallic
iridium(III) complexes IrA1 and IrB1, which chelates IrCp*Cl (Cp*
= 1,2,3,4,5-pentamethylcyclopentadiene) to afford trinuclear complexes
IrA3 and IrB3. Insights into the photophysical and electrochemical
parameters of the complexes were obtained by a time-dependent density
functional theory study. The synthesized complexes IrA2, IrA3, IrB2,
and IrB3 were found to be nontoxic to human MCF7 breast carcinoma
cells. However, the photoexcitation of complexes using LED light could
effectively trigger intracellular reactive oxygen species (ROS) generation,
leading to cell death. Furthermore, to check the organelle-specific
localization of IrA2 and IrB2, we observed that both complexes could
selectively localize in the endoplasmic reticulum. In contrast, trinuclear
IrA3 and IrB3 accumulate in the nuclei. The photoexcitation of complexes
using LED light could effectively trigger intracellular reactive oxygen
species (ROS) generation, leading to cell death.