A series of Re(I) tricarbonyl complexes with the general formula, fac-[Re(CO)3(2,2’-bipyridine)(X)]-/0 (X= L-cysteine; N-acetyl-L-cysteine; thiosulfate) were characterized using spectroscopic techniques and single-crystal X-ray diffraction. Photophysical, as well as singlet oxygen (1O2) generation and CO releasing properties were assessed. Cell viability of the complexes against the MDA-MB-231 breast cancer cell line were determined. Cellular localization and accumulation were investigated using synchrotron-based X-ray fluorescence microscopy (XFM). The results of this study show the cytotoxicity, cellular uptake and photophysical properties of fac-[Re(CO)3(bpy)X]+/0/- complexes (X= H2O, HCys-, NAC2-, S2O32-; bpy=2,2’-bipyridine). The cytotoxicity of fac-[Re(CO)3(bpy)(H2O)]+ is diminished when the aqua ligand is replaced by cysteine or thiosulfate.