Photoactivatable Organometallic Pyridyl Ruthenium(II) Arene Complexes

Abstract

The synthesis and characterization of a family of piano-stool Ru II arene complexes of the type [(η 6 -arene)Ru(N,N')(L)] [PF 6 ] 2 where arene is para-cymene (p-cym), hexamethylbenzene (hmb) or indane (ind); N,N' is 2,2'-bipyrimidine (bpm), 1,10-phenanthroline (phen), 1,10-phenanthroline-5,6-dione (phendio), 4,7-diphenyl-1,10-phenanthroline (bathophen), and L is pyridine (Py), 4-methylpyridine (4-MePy), 4-methoxypyridine (4-MeOPy), 4,4'-bipyridine (4,4'-biPy), 4-phenylpyridine (4-PhPy), 4-benzylpyridine (4-BzPy), 1,2,4-triazole (trz), 3-acetylpyridine (3-AcPy), nicotinamide (NA), or 3-acetatepyridine (3-AcOPy) are reported; including the X-ray crystal structures of [(η 6 -p-[(η 6 -p-cym)Ru(phen)(Py)] 2+ (10), and [(η 6 -ind)Ru(bpy)(Py)] 2+ (13). These complexes can selectively photodissociate the monodentate ligand (L) when excited with UVA or white light allowing strict control of the formation of the reactive aqua species [(η 6 -arene)Ru(N,N')(OH 2 )] 2+ that otherwise would not form in the dark. The photoproducts were characterized by UV-vis absorption and 1 H NMR spectroscopy. DFT and TD-DFT calculations were employed to characterize the excited states and to obtain information on the photochemistry of the complexes. All the Ru II pyridine complexes follow a relatively similar photochemical L-ligand dissociation mechanism, likely to occur from a series of 3 MC triplet states with dissociative character. The photochemical process proved to be much more efficient when UVA-range irradiation was used. More strikingly, light activation was used to photo-trigger binding of these potential anticancer agents with discriminating preference towards 9-ethylguanine (9-EtG) over 9-ethyladenine (9-EtA). Calf-thymus (CT)-DNA binding studies showed that the irradiated complexes bind to CT-DNA whereas the non-irradiated forms, bind negligibly.

Cytotoxicity of Ru(II) piano–stool complexes with chloroquine and chelating ligands against breast and lung tumor cells: Interactions with DNA and BSA

“…The UV-Vis absorption spectra of the complexes in dimethylsulfoxide ( Figure 1S and Table 1) were characterized by an intense high energy band centered at about 300 nm, which can be assigned to a ligand-localized, intra-ligand π-π* transition. Complexes 1-5 exhibited lower-energy bands in the range of 340-400 nm, which can be attributed as metal to ligand charge transfer (MLCT) transitions from Ru (dπ) to the ligand (π*) [28][29]. substituting the chloride atom [31].…”

The photochemistry of transition metal complexes using density functional theory

“…In a recent study, Sokolov & Schaefer [93,94]. It has been shown that irradiated Ru-arene complexes bind to nucleobases such as 9-ethylguanine and to calf thymus DNA, whereas non-irradiated complexes bind negligibly.…”

Synchrotron ultrafast techniques for photoactive transition metal complexes

“…A challenge for the TR-XSS technique is to extend its use to detect photoprocesses involving the release of multiatomic fragments formed by low-Z atoms such as, for example, C, N and O. For these reasons and for our interest in the photochemistry of Ru-diimine complexes [86,[230][231][232][233], we investigated, by TR-XSS, the ligand photodissociation reaction of the model compound cis-[Ru(bpy) 2 (py) 2 ]Cl 2 in aqueous solution (20 mm solution, ξ = 1.1 × 10 −4 ) [54]. This Ru-polypiridil derivative efficiently releases one pyridine ligand upon excitation of the metal-to-ligand charge-transfer (MLCT) band and subsequently coordinates a solvent molecule.…”