Half-sandwich Iridium(III) complexes with triphenylamine-substituted dipyridine frameworks and bioactivity applications

Nine half-sandwich IrIII complexes [(η5-Cpx)Ir(NˆN)Cl]PF6, where Cpx is Cp* or its phenyl Cpxph or biphenyl Cpxbiph derivative and NˆN is a triphenylamine (TPA)-substituted bipyridyl ligand, were synthesized and characterized. MTT assay revealed that the complexes show potent antitumor activity with IC50 values of 1.2–36.3 μM against A549 lung cancer cells. The IrIII complexes bound to BSA and oxidized NADH to NAD+, leading to production of H2O2 (maximum turnover number, 37.9), which plays an important role in regulating cell apoptosis. Confocal microscopy showed that the complexes could target lysosomes effectively in cells with a high Pearson's colocalization coefficient (∼0.5) and followed an energy-dependent cellular uptake mechanism.