Photoswitchable arene ruthenium and pentamethylcyclopentadienyl rhodium complexes containing o-sulfonamide azobenzene ligands: Synthesis, characterization and cytotoxicity

A new series of arene chlorido ruthenium and pentamethylcyclopentadienyl chlorido rhodium complexes containing o-sulfonamide azobenzene ligands with an exocyclic N=N bond coordination pattern have been synthesized. These complexes undergo readily E -> Z photoisomerization followed by thermal Z -> E isomerization (upon resting in the dark). The ruthenium complexes showed low-micromole-ranged cytotoxicity towards a panel of cancer cells. Western blotting and flow cytometric analyses suggest that 1) they are potent apoptotic inducers for cancer cells, probably through a caspase-3 dependent apoptotic pathway, and that 2) they have a much stronger ability to induce HeLa cancer cell apoptosis than cisplatin, a commercial anticancer drug. (C) 2016 Elsevier B.V. All rights reserved.