Visible Light-Activated CO Release and ¹O₂ Photosensitizer Formation with Ru(II),Mn(I) Complexes

Abstract

Two diimine-bridged Ru(II),Mn(I) complexes with a [(bpy)Ru(BL)Mn(CO)Br] architecture, where bpy = 2,2'-bipyridine and BL = 2,3-bis(2-pyridyl)pyrazine (dpp; Ru(dpp)Mn) or 2,2'-bipyrimidine (bpm; Ru(bpm)Mn), were designed to both dissociate multiple equivalents of CO and produce O when irradiated with visible light. Analysis of the complexes by Fourier transform infrared (FTIR) spectroscopy and cyclic voltammetry suggest a stronger π-accepting ability for bpm compared to that of dpp. Both complexes absorb light throughout the UV and visible regions with lowest energy absorption bands comprising overlapping Ru(dπ)→BL(π*) and Mn(dπ)→BL(π*) singlet metal-to-ligand charge transfer (MLCT) and Br(p)→dpp(π*) singlet halide-to-ligand charge transfer (XLCT) transitions. This lowest energy band is centered at 510 nm (ε = 12 000 Mcm) for Ru(dpp)Mn and 553 nm (ε = 3240 Mcm) for Ru(bpm)Mn, and the absorption band extends to nearly 700 nm in each case. Irradiation with visible light (both 470 and 627 nm) releases all three CO ligands, as observed by a combination of UV-vis, FTIR, and gas chromatography. The exchange of the first CO ligand with a solvent molecule occurs more efficiently for Ru(dpp)Mn (Φ = 0.22 ± 0.03 in HO; 0.37 ± 0.06 in CHCN) than for Ru(bpm)Mn (Φ = 0.049 ± 0.008 in HO and 0.16 ± 0.03 in CHCN), and the CO dissociation efficiency is unaffected by irradiation wavelength. The differences between Ru(dpp)Mn and Ru(bpm)Mn are proposed to result from the variation in electron density distribution across each formally reduced BL in the Mn(dπ)→BL(π*) MLCT excited state based on the nature of BL. Exhaustive photolysis causes the decomplexation of oxidized Mn(II), and the resulting [(bpy)Ru(BL)] complexes produce O with quantum yields (Φ) of 0.37 ± 0.03 and 0.16 ± 0.01 for Ru(dpp) and Ru(bpm), respectively, with 460 nm irradiation. This bimetallic architecture presents the opportunity to use visible light to codeliver both CO and O, both of which have biological relevance in photoactivated therapeutics, with spatiotemporal control.

Trifluoromethyl substitution enhances photoinduced activity against breast cancer cells but reduces ligand exchange in Ru(ii) complex

“…[1][2][3][4] As such, these complexes exhibit useful photophysical properties for many applications, such as luminescent sensors, 5,6 photoswitches, 7,8 molecular machines, 9 photoredox catalysis, 10,11 and solar energy conversion. [12][13][14][15][16][17] Ruthenium(II) complexes have also been shown to act as agents for photodynamic therapy (PDT) through the sensitization of 1 O 2 , [18][19][20][21] and for the photoinduced release of therapeutics with spatiotemporal control, photochemotherapy (PCT). [22][23][24][25] Whereas PDT requires a stable complex, the latter features the dissociation of a ligand upon irradiation with low energy, red or near-IR light.…”

Photochemistry of P,N-bidentate rhenium(i) tricarbonyl complexes: reactive species generation and potential application for antibacterial photodynamic therapy

“…[39][40][41] Recently, the synergic action of singlet oxygen generation and photoinduced release of carbon monoxide by tricarbonyl metal complexes has been proposed as promising treatment against cancer. [42][43][44] In this framework, rhenium complexes have been classied as good photoCORMs and photosensitizers for singlet oxygen generation, holding also great potential for antibacterial treatments. 45 Today, there is an urgent need for novel agents to ght bacterial infections.…”

A red light‐activable MnI(CO)3‐functionalized gold nanocomposite as the anticancer prodrug with theranostic potential

“…[ 15–30 ] The salutary effect of a low dose of CO has prompted research on the photoactivated release of exogenous CO from CO‐releasing molecules (CORMs) with spatial and temporal resolution for clinical applications, including cancer therapy. [ 31–48 ] However, the delivery, tumor specificity, and retention of CORMs in malignant tumors are formidable challenges in utilizing photoCORMs for cancer therapy. [ 42 ]…”

“…[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] The salutary effect of a low dose of CO has prompted research on the photoactivated release of exogenous CO from CO-releasing molecules (CORMs) with spatial and temporal resolution for clinical applications, including cancer therapy. [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] However, the delivery, tumor specificity, and retention of CORMs in malignant tumors are formidable challenges in utilizing photoCORMs for cancer therapy. [42] Gold nanoparticles (AuNPs) and gold nanorods have emerged as ideal drug-delivery platforms because of their easy synthesis, large surface areas, good biocompatibility, and tunable and facile functionalization.…”