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The Influence of Some Axial Ligands on Ruthenium-Phthalocyanine Complexes: Chemical, Photochemical, and Photobiological Properties.

ABSTRACT: This work presents a new procedure to synthesize ruthenium-phthalocyanine complexes and uses diverse spectroscopic techniques to characterize trans-[RuCl(Pc)DMSO] (I) (Pc = phthalocyanine) and trans-[Ru(Pc)(4-ampy)₂] (II) (4-ampy = 4-aminopyridine). The triplet excited-state lifetimes of (I) measured by nanosecond transient absorption showed that two processes occurred, one around 15 ns and the other around 3.8 ?s. Axial ligands seemed to affect the singlet oxygen quantum yield. Yields of 0.62 and 0.14 were achieved for (I) and (II), respectively. The lower value obtained for (II) probably resulted from secondary reactions of singlet oxygen in the presence of the ruthenium complex. We also investigate how axial ligands in the ruthenium-phthalocyanine complexes affect their photo-bioactivity in B16F10 murine melanoma cells. In the case of (I) at 1 ?mol/L, photosensitization with 5.95 J/cm² provided B16F10 cell viability of 6%, showing that (I) was more active than (II) at the same concentration. Furthermore, (II) was detected intracellularly in B16F10 cell extracts. The behavior of the evaluated ruthenium-phthalocyanine complexes point to the potential use of (I) as a metal-based drug in clinical therapy. Changes in axial ligands can modulate the photosensitizer activity of the ruthenium phthalocyanine complexes.

SUBMITTER: Martins TJ

PROVIDER: S-EPMC7835839 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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The Influence of Some Axial Ligands on Ruthenium-Phthalocyanine Complexes: Chemical, Photochemical, and Photobiological Properties.

Martins Tássia Joi TJ Negri Laisa Bonafim LB Pernomian Laena L Faial Kelson do Carmo Freitas KDCF Xue Congcong C Akhimie Regina N RN Hamblin Michael R MR Turro Claudia C da Silva Roberto S RS

Frontiers in molecular biosciences 20210112

This work presents a new procedure to synthesize ruthenium-phthalocyanine complexes and uses diverse spectroscopic techniques to characterize trans-[RuCl(Pc)DMSO] (I) (Pc = phthalocyanine) and trans-[Ru(Pc)(4-ampy)2] (II) (4-ampy = 4-aminopyridine). The triplet excited-state lifetimes of (I) measured by nanosecond transient absorption showed that two processes occurred, one around 15 ns and the other around 3.8 μs. Axial ligands seemed to affect the ...[more]

PMID: 33511155

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Project description:A new family of cyclometalated ruthenium(II) complexes [Ru(N^N)2(C^N)]+ derived from the ?-extended benzo[h]imidazo[4,5-f]quinolone ligand appended with thienyl groups (n = 1-4, compounds 1-4) was prepared and its members were characterized for their chemical, photophysical, and photobiological properties. The lipophilicities of 1-4, determined as octanol-water partition coefficients (log Po/w), were positive and increased with the number of thienyl units. The absorption and emission bands of the C^N compounds were red-shifted by up to 200 nm relative to the analogous Ru(II) diimine systems. All of the complexes exhibited dual emission with the intraligand fluorescence (1IL, C^N-based) shifting to lower energies with increasing n and the metal-to-ligand charge transfer phosphorescence (3MLCT, N^N-based) remaining unchanged. Compounds 1-3 exhibited excited state absorption (ESA) profiles consistent with lowest-lying 3MLCT states when probed by nanosecond transient absorption (TA) spectroscopy with 532 nm excitation and had contributions from 1IL(C^N) states with 355 nm excitation. These assignments were supported by the lifetimes observed (<10 ns for the 1IL states and around 20 ns for the 3MLCT states) as well as a noticeable ESA for 3 with 355 nm excitation that did not occur with 532 nm excitation. Compound 4 was the only member of the family with two 3MLCT emissive lifetimes (15, 110 ns), and the TA spectra collected with both 355 and 532 nm excitation was assigned to the 3IL state, which was corroborated by its 4-6 ?s lifetime. The ESA for 4 had a rise time of approximately 10 ns and an initial decay of 110 ns, which suggests a possible 3MLCT-3IL excited state equilibrium that results in delayed emission from the 3MLCT state. Compound 4 was nontoxic toward human skin melanoma cells (SKMEL28) in the dark (EC50 = >300 ?M); 1-3 were cytotoxic and yielded EC50 values between 1 and 20 ?M. The photocytotoxicites with visible light ranged from 87 nM with a phototherapeutic index (PI) of 13 for 1 to approximately 1 ?M (PI = >267) for 4. With red light, EC50 values varied from 270 nM (PI = 21) for 3 to 12 ?M for 4 (PI = >25). The larger PIs for 4, especially with visible light, were attributed to the much lower dark cytotoxicity for this compound. Because the dark cytotoxicity contributes substantially to the observed photocytotoxicity for 1-3, it was not possible to assess whether the 3IL state of 4 led to a much more potent phototoxic mechanism in the absence of dark toxicity. There was no stark contrast in cellular uptake and accumulation by laser scanning confocal and differential interference contrast microscopy to explain the large differences in dark toxicities between 1-3 and 4. Nevertheless, the study highlights a new family of Ru(II) C^N complexes where ?-conjugation beyond a certain point results in low dark cytotoxicity with high photocytotoxicity, opposing the notion that cyclometalated Ru(II) systems are too toxic to be phototherapeutic agents.

Dataset Information

The Influence of Some Axial Ligands on Ruthenium-Phthalocyanine Complexes: Chemical, Photochemical, and Photobiological Properties.

Publications

The Influence of Some Axial Ligands on Ruthenium-Phthalocyanine Complexes: Chemical, Photochemical, and Photobiological Properties.

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