fac-[Re(phen)(CO)3(MMB)]

fac-[Re(phen)(CO)3(MMB)] is a neutral rhenium(I) tricarbonyl complex that has been investigated for its cell imaging properties and anti-proliferative activity, particularly in human breast cancer cell lines such as MDA-MB-231 and MCF-7. It exhibits anti-proliferative effects, with an IC50 of approximately 10 μM at 72 hours treatment in thiol-depleted MDA-MB-231 cells. Notably, unlike some related complexes, its activity is not diminished by the presence of extracellular glutathione, suggesting a distinct mechanism of action related to cellular thiols. The complex also shows promise as an organelle probe for multimodal imaging, including phosphorescence, carbonyl tag for vibrational spectroscopy, and as a rhenium tag for X-ray fluorescence microscopy, with specific localization in lysosomes and partial migration to mitochondria over longer treatment times.