Ruthenium pincer complexes for light activated toxicity: Lipophilic groups enhance toxicity

Sun, Yifei; Das, Sanjit; Brown, Spenser R; Blevins, Emily  R.; Qu, Fengrui; Ward, Nicholas A. B.; Gregory, Shawn A.; Boudreaux, Chance M.; Kim, Yonghyun; Papish, Elizabeth T.

doi:10.1016/j.jinorgbio.2022.112110

Cited by 5 publications

(7 citation statements)

References 34 publications

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“…This procedure is similar to our recently reported syntheses of related complexes . Complex 2A was then treated with silver triflate to replace the chloride with acetonitrile (from the solvent) to form complex 2B in high yield (86%) . Complexes 4A and 4B were synthesized in a similar manner, in 67 and 83% yields, respectively, but starting from complex 3 bearing benzimidazole-derived NHCs .…”

Section: Results and Discussionmentioning

confidence: 74%

“…51 Complexes 4A and 4B were synthesized in a similar manner, in 67 and 83% yields, respectively, but starting from complex 3 bearing benzimidazole-derived NHCs. 51 The acetonitrile in 4B was substituted with a bromide ligand to make the complex 4C in 62% yield by treating 4B with n Et 4 NBr in methanol. In all of the complexes in this study, the coordination sphere of the ruthenium is completed by a tridentate CNC pincer, a bidentate bpy, and a monodentate halide (anionic) or acetonitrile (neutral) ligand.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…34 Complex 2A was then treated with silver triflate to replace the chloride with acetonitrile (from the solvent) to form complex 2B in high yield (86%). 51 Complexes 4A and 4B were synthesized in a similar manner, in 67 and 83% yields, respectively, but starting from complex 3 bearing benzimidazole-derived NHCs. 51 The acetonitrile in 4B was substituted with a bromide ligand to make the complex 4C in 62% yield by treating 4B with n Et 4 NBr in methanol.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Ruthenium (II) Complexes of CNC Pincers and Bipyridine in the Photocatalytic CO₂ Reduction Reaction to CO Using Visible Light: Catalysis, Kinetics, and Computational Insights

et al. 2023

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A series of five ruthenium (II) complexes containing a tridentate CNC pincer ligand, a bidentate 2,2′-bipyridine (bpy) ligand, and a monodentate ligand (chloride, bromide, or acetonitrile) were synthesized. The CNC pincer ligands used imidazole or benzimidazole-derived N-heterocyclic carbenes (NHCs) as the C donors and a 4-methoxy-substituted central pyridyl ring as the N donor. All of the complexes were characterized by analytical, spectroscopic, and single-crystal X-ray diffraction methods. These complexes were used as catalysts for visible-light-driven CO2 reduction in the presence and absence of an external photosensitizer (PS). Notably, complex 4C with a benzimidazole-derived CNC pincer ligand and bromide as the monodentate ligand was the most active catalyst tested for both sensitized and self-sensitized CO2 reduction. Thus, this catalyst was the subject of further mechanistic studies using transient absorption spectroscopy (TAS), absorption spectroelectrochemistry (SEC), and computational studies. A mechanism has been proposed for self-sensitized CO2 reduction involving (1) light excitation of the catalyst, (2) reduction by sacrificial donors, (3) halide loss, and (4) CO2 binding to form [RuCO 2 ] + as the catalyst resting state. The timeline for these steps and the structures of key intermediates are all supported by experimental observations (including TAS and SEC) and supporting computational studies. Subsequent steps in the cycle past [RuCO 2 ] + were not experimentally observable, but they are supported by computations. Experiments were also used to explain the differences observed for sensitized catalysis. Catalyst 4C is an unusually active catalyst for both sensitized and self-sensitized CO2 reduction, and thus being able to understand how it functions and which steps are turnover-limiting is an important development facilitating the design of commercially viable catalysts for solar fuel formation.

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Section: Results and Discussionmentioning

confidence: 74%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

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Ruthenium (II) Complexes of CNC Pincers and Bipyridine in the Photocatalytic CO₂ Reduction Reaction to CO Using Visible Light: Catalysis, Kinetics, and Computational Insights

et al. 2023

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“…Importantly, the complexes with a cytostatic property were less active on primary, non-transformed human dermal fibroblasts. While this property of the complexes suggests a selectivity for transformed neoplastic cells over non-transformed cells, the anticipated therapeutic window is relatively narrow as compared to previous observations of complexes with ligands of similar [ 32 , 45 , 46 ] or different structure [ 76 , 77 ].…”

Section: Discussionmentioning

confidence: 71%

Half-Sandwich Type Platinum-Group Metal Complexes of C-Glucosaminyl Azines: Synthesis and Antineoplastic and Antimicrobial Activities

et al. 2023

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While platinum-based compounds such as cisplatin form the backbone of chemotherapy, the use of these compounds is limited by resistance and toxicity, driving the development of novel complexes with cytostatic properties. In this study, we synthesized a set of half-sandwich complexes of platinum-group metal ions (Ru(II), Os(II), Ir(III) and Rh(III)) with an N,N-bidentate ligand comprising a C-glucosaminyl group and a heterocycle, such as pyridine, pyridazine, pyrimidine, pyrazine or quinoline. The sugar-containing ligands themselves are unknown compounds and were obtained by nucleophilic additions of lithiated heterocycles to O-perbenzylated 2-nitro-glucal. Reduction of the adducts and, where necessary, subsequent protecting group manipulations furnished the above C-glucosaminyl heterocycles in their O-perbenzylated, O-perbenzoylated and O-unprotected forms. The derived complexes were tested on A2780 ovarian cancer cells. Pyridine, pyrazine and pyridazine-containing complexes proved to be cytostatic and cytotoxic on A2780 cells, while pyrimidine and quinoline derivatives were inactive. The best complexes contained pyridine as the heterocycle. The metal ion with polyhapto arene/arenyl moiety also impacted on the biological activity of the complexes. Ruthenium complexes with p-cymene and iridium complexes with Cp* had the best performance in ovarian cancer cells, followed by osmium complexes with p-cymene and rhodium complexes with Cp*. Finally, the chemical nature of the protective groups on the hydroxyl groups of the carbohydrate moiety were also key determinants of bioactivity; in particular, O-benzyl groups were superior to O-benzoyl groups. The IC50 values of the complexes were in the low micromolar range, and, importantly, the complexes were less active against primary, untransformed human dermal fibroblasts; however, the anticipated therapeutic window is narrow. The bioactive complexes exerted cytostasis on a set of carcinomas such as cell models of glioblastoma, as well as breast and pancreatic cancers. Furthermore, the same complexes exhibited bacteriostatic properties against multiresistant Gram-positive Staphylococcus aureus and Enterococcus clinical isolates in the low micromolar range.

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“…This procedure is similar to our published methods for the synthesis of Ru CNC pincer complexes. 25,26 These nickel complexes were precipitated out of the reaction mixture as yellow to orange solids in moderate to high yields, and they have limited solubility in common organic solvents. Despite similar conditions, the imidazole and benzimidazole-derived products contain different counteranions as shown in the 19 F-NMR spectra and the crystal structures (Scheme 1 and Table 1).…”

Section: ■ Introductionmentioning

confidence: 99%

Sensitized and Self-Sensitized Photocatalytic CO₂ Reduction to HCO₂^– and CO under Visible Light with Ni(II) CNC-Pincer Catalysts

Manafe,

Le,

Lambert

et al. 2024

ACS Catal.

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Robust earth-abundant transition metal-based photocatalysts are needed for photocatalytic CO2 reduction. A series of six Ni(II) complexes have been synthesized with a tridentate CNC pincer ligand composed of two imidazole or benzimidazole-derived N-heterocyclic carbene (NHC) rings and a pyridyl ring with different R substituents (R = OMe, Me, H) para to N of the pyridine ring. These complexes have been characterized by using spectroscopic, analytic, and crystallographic methods. The electrochemical properties of all complexes were studied by cyclic voltammetry under N2 and CO2 atmospheres. Photocatalytic reduction of CO2 to CO and HCO2 – was analyzed using all of the complexes in the presence and absence of an external photosensitizer (PS). All of these complexes are active as photocatalysts for CO2 reduction with and without the presence of an external PS with appreciable turnover numbers (TONs) for formate (HCO2 –) production and typically lower amounts of CO. Notably, all Ni(II) CNC-pincer complexes in this series are also active as self-sensitized photocatalysts. Complex 4 Me with a benzimidazole-derived CNC pincer ligand was found to be the most active self-sensitized photocatalyst. Ultrafast transient absorption spectroscopy (TAS) experiments and computational studies were performed to understand the mechanism of these catalysts. Whereas sensitized catalysis involves halide loss to produce more active complexes, self-sensitized catalysis requires some halide to remain coordinated to allow for favorable electron transfer between the excited nickel complex and the sacrificial electron donor. This then allows the nickel complex to undergo CO2 reduction catalysis via NiI or Ni0 catalytic cycles. The two active species (NiI and Ni0) demonstrate distinct reactivity and selectivity which influences the formation of CO vs formate as the product.

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Ruthenium pincer complexes for light activated toxicity: Lipophilic groups enhance toxicity

Cited by 5 publications

References 34 publications

Ruthenium (II) Complexes of CNC Pincers and Bipyridine in the Photocatalytic CO₂ Reduction Reaction to CO Using Visible Light: Catalysis, Kinetics, and Computational Insights

Ruthenium (II) Complexes of CNC Pincers and Bipyridine in the Photocatalytic CO₂ Reduction Reaction to CO Using Visible Light: Catalysis, Kinetics, and Computational Insights

Half-Sandwich Type Platinum-Group Metal Complexes of C-Glucosaminyl Azines: Synthesis and Antineoplastic and Antimicrobial Activities

Sensitized and Self-Sensitized Photocatalytic CO₂ Reduction to HCO₂^– and CO under Visible Light with Ni(II) CNC-Pincer Catalysts

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Ruthenium pincer complexes for light activated toxicity: Lipophilic groups enhance toxicity

Cited by 5 publications

References 34 publications

Ruthenium (II) Complexes of CNC Pincers and Bipyridine in the Photocatalytic CO2 Reduction Reaction to CO Using Visible Light: Catalysis, Kinetics, and Computational Insights

Ruthenium (II) Complexes of CNC Pincers and Bipyridine in the Photocatalytic CO2 Reduction Reaction to CO Using Visible Light: Catalysis, Kinetics, and Computational Insights

Half-Sandwich Type Platinum-Group Metal Complexes of C-Glucosaminyl Azines: Synthesis and Antineoplastic and Antimicrobial Activities

Sensitized and Self-Sensitized Photocatalytic CO2 Reduction to HCO2– and CO under Visible Light with Ni(II) CNC-Pincer Catalysts

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Product

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Ruthenium (II) Complexes of CNC Pincers and Bipyridine in the Photocatalytic CO₂ Reduction Reaction to CO Using Visible Light: Catalysis, Kinetics, and Computational Insights

Ruthenium (II) Complexes of CNC Pincers and Bipyridine in the Photocatalytic CO₂ Reduction Reaction to CO Using Visible Light: Catalysis, Kinetics, and Computational Insights

Sensitized and Self-Sensitized Photocatalytic CO₂ Reduction to HCO₂^– and CO under Visible Light with Ni(II) CNC-Pincer Catalysts