Structurally Simple Osmium(II) Polypyridyl Complexes as Photosensitizers for Photodynamic Therapy in the Near Infrared.

Five osmium(II) polypyridyl complexes of the general formula [Os(4,7-diphenyl-1,10-phenanthroline)2 L]2+ were synthesized as photosensitizers for photodynamic therapy by varying the nature of the ligand L. Thanks to the pronounced π-extended structure of the ligands and the heavy atom effect provided by the osmium center, these complexes exhibit a high absorption in the near-infrared (NIR) region (up to 740 nm), unlike related ruthenium complexes. This led to a promising phototoxicity in vitro against cancer cells cultured as 2D cell layers but also in multicellular tumor spheroids upon irradiation at 740 nm. The complex [Os(4,7-diphenyl-1,10-phenanthroline)2 (2,2'-bipyridine)]2+ was found to be the most efficient against various cancer cell lines, with high phototoxicity indexes. Experiments on CT26 tumor-bearing BALB/c mice also indicate that the OsII complexes could significantly reduce tumor growth following 740 nm laser irradiation. The high phototoxicity in the biological window of this structurally simple complex makes it a promising photosensitizer for cancer treatment.

Crystal structure of tris-(4,7-diphenyl-1,10-phenanthroline-κ2 N,N')cobalt(III) tris-(hexa-fluoro-phosphate) monohydrate.

The title compound, [Co(C72H48N6)](PF6)3·H2O, crystallizes with one tripositive complex mol-ecule, three hexa-fluoro-phosphate anions and one solvent mol-ecule of water in the asymmetric unit. The N6 coordination set around the central CoIII atom defines a distorted octa-hedral environment. Four fluorine atoms of one hexa-fluoro-phosphate anion are disordered over two sets of positions with site-occupancy factors of 0.697 (5) and 0.303 (5). In the crystal, inter-molecular π-π stacking inter-actions, C-H⋯π, C-H⋯F and O-H⋯F and inter-actions are present.