Selective Photoinduced Ligand Exchange in a New Tris–Heteroleptic Ru(II) Complex

Abstract

The complex cis-[Ru(biq)(phen)(CH3CN)2](2+) (1, biq = 2,2'-biquinoline, phen = 1,10-phenathroline) displays selective photosubstitution of only one CH3CN ligand with a solvent molecule upon irradiation with low energy light (λ(irr) ≥ 550 nm), whereas both ligands exchange with λ(irr) ≥ 420 nm. In contrast, [Ru(phen)2(CH3CN)2](2+) (2) and [Ru(biq)2(CH3CN)2](2+) (3) exchange both CH3CN ligands with similar rates upon irradiation with a broad range of wavelengths. The photolysis of 1 in the presence of pyridine (py) results in the formation of the intermediate cis-[Ru(biq)(phen)(py)(MeCN)](2+), which was isolated and characterized by X-ray crystallography, revealing that the CH3CN positioned trans to the phen ligand is more photolabile than that positioned trans to the biq ligand when irradiated with low energy light. These results are explained using the calculated stabilities of the two possible products, together with the molecular orbitals involved in the lowest energy excited state.

Steric and Electronic Factors Associated with the Photoinduced Ligand Exchange of Bidentate Ligands Coordinated to Ru(II)

“…No changes are observed in the spectra when the complex is kept in the dark for over 4 h in H 2 O and CH 3 CN. The peaks of the photoproduct in water at 585 nm and that in CH 3 CN at 535 nm are in agreement with those reported for [Ru (biq) 2 (H 2 O) 2 ] 2+ and [Ru(biq) 2 (CH 3 CN) 2 ] 2+ , respectively (46), indicating that the dpb ligand is exchanging with the two solvent molecules.…”

Red‐Light‐Controlled Release of Drug–Ru Complex Conjugates from Metallopolymer Micelles for Phototherapy in Hypoxic Tumor Environments

“…Because solid tumors have a hypoxic microenvironment especially in the areas far away from the blood vessels (>70 µm), PDT does not work in hypoxic tumor environment. In contrast, PACT using Ru complexes is better suited than PDT for hypoxic tumor treatment because ligand photosubstitution is oxygen independent . Thus, PACT represents a promising approach against hypoxic tumors.…”

An Amphiphilic Ruthenium Polymetallodrug for Combined Photodynamic Therapy and Photochemotherapy In Vivo

“…[3d] Additionally, Ru complexes can directly absorb visible or near‐infrared (NIR) light, which can penetrate deeply into tissue and causes less photodamage to biological systems than UV light . Photocaged Ru complexes can be activated by NIR light via a one‐photon process[4a,8] or a photon upconversion process. [7b,9] Because of these interesting features, photocaged Ru complexes have had many successful applications in vitro.…”