nm, respectively (supporting information). The lifetimes of emission are in the µs range and the complex is sensitive to the presence of oxygen (k[O2] = 0.31-0.61 10 9 /L.mol -1 .s, in EtOH and CH2Cl2 respectively). The emission is slightly sensitive to the solvent polarity with a 4 nm (~194 cm -1 ) bathochromic shift from CH2Cl2 to EtOH. Furthermore, at low temperature in a glassy solution in benzonitrile, complex 8 displays a structured emission accompanied with a small bathochromic shift (see SI). Thus, the emission can be attributed to the radiative deactivation of a mixture of 3 IL/ MLCT excited states to the ground state. Such interplay between excited states is well documented in cyclometallated iridium(III) complexes. The photophysical parameters and emission profile, i.e. λem and Φ, are highly similar to those observed for similar complexes with phenanthroline ancillary ligand and 2-phenylquinoline as cyclometallating ligand. The ability of complex 8 to sensitize cytotoxic singlet oxygen was measured by a comparative method using phenalenone (φΔ(CHCl3) = 0.97 ± 0.02) as reference. The quantum yield of 1 O2 generation was found to be 0.68. The 1 O2 species facilitate cell death through oxidation of surrounding biomolecules, leading to the production of cytotoxic agents. Usually, cell death occurs through initiation of apoptotic and necrotic pathways, and less frequently through oncosis or ferroptosis, all of which are mechanisms that underpin PDT for the treatment of cancer. The viability of utilising the brightly luminescent complex 8 for bioimaging applications using a 488 nm excitation source was first assess throughflow cytometry analysis. Initial experiments indicated that treatment of T lymphoblast Jurkat cells (ATCC ® TIB-152 ™ ) with 1µM solution of the complex 8 in PBS buffer led to uptake of the complex by 97% of the cells within 30 minutes (supporting information), confirming that complex 8 is capable of staining live mammalian live in vitro. Complex 8