Ruthenium Complexes Research Articles

Kinetic study on bimolecular photochemical quenching of tris(2,2'-bipyridyl)ruthenium(II) complex in water-ethylene glycol binary media.

The bimolecular photochemical quenching of the tris(2,2'-bipyridyl)ruthenium (II) complex by ferricyanide ions in water-ethylene glycol binary media was investigated using a spectrophotometric approach, as previously reported by our research group. Time-resolved spectroscopy revealed that dynamic photochemical quenching occurred via a diffusion-dominated pathway. The static quenching process was found to occur significantly when the concentration of ethylene glycol was greater than 40 wt%. The analysis of the Stern-Volmer plots revealed that the emitters and quenchers tended to show ionic associations in water-ethylene glycol compared to our previous results with a water-glycerol binary solvent system. This is attributed to hydrophobicity, which is consistent with pioneering works that report that the addition of ethylene glycol to pure water forms hydrophobic regions, leading to dehydration of the complex ions.

Selective Oxidative Scission of Olefins to Aldehydes Enabled by Ruthenium Complexes Containing Salicylaldimine Ligands

ABSTRACTTreatment of Ru3(CO)12 with salicylaldimine ligands [ArNCH(3‐tBuC6H3OH) [ArC6H5 (L1H); 4‐OMeC6H4 (L2H); 4‐MeC6H4 (L3H); 2,4,6‐Me3C6H2 (L4H); 4‐ClC6H4 (L5H); 4‐BrC6H4 (L6H)] in refluxing toluene afforded six bis‐ligand mononuclear ruthenium carbonyl complexes [ArNCH(3‐tBuC6H3O)]2Ru(CO)2 1a–1f in good yields. All of the Ru(II) complexes were characterized using IR, NMR, and elemental analysis. The molecular structures of complexes 1a, 1b, 1e, and 1f were further confirmed through X‐ray diffraction analysis. Additionally, the catalytic performance of these complexes was investigated in the oxidation of olefins to aldehydes, using TBHP as the oxidant in refluxing trichloromethane. With 1.0 mol% catalyst loading, these ruthenium complexes displayed high reactivity and good functional‐group compatibility, selectivity providing the corresponding oxidation product aldehydes in 73%–94% yields.

Metal Ruthenium Complexes Treat Spinal Cord Injury By Alleviating Oxidative Stress Through Interaction With Antioxidant 1 Copper Chaperone Protein.

Oxidative stress is a major factor affecting spinal cord injury (SCI) prognosis. A ruthenium metal complex can aid in treating SCI by scavenging reactive oxygen species via a protein-regulated mechanism to alleviate oxidative stress. This study aimed to introduce a pioneering strategy for SCI treatment by designing two novel half-sandwich ruthenium (II) complexes containing diverse N^N-chelating ligands. The general formula is [(η6-Arene)Ru(N^N)Cl]PF6, where arene is either 2-phenylethanol-1-ol (bz-EA) or 3-phenylpropanol-1-ol (bz-PA), and the N^N-chelating ligands are fluorine-based imino-pyridyl ligands. This study shows that these ruthenium metal complexes protect neurons by scavenging reactive oxygen species. Notably, η6-Arene substitution from bz-PA to bz-EA significantly enhances reactive oxygen species scavenging ability and neuroprotective effect. Additionally, molecular dynamics simulations indicate that the ruthenium metal complex increases Antioxidant 1 Copper Chaperone protein expression, reduces oxidative stress, and protects neurons during SCI treatment. Furthermore, ruthenium metal complex protected spinal cord neurons and stimulated their regeneration, which improves electrical signals and motor functions in mice with SCI. Thus, this treatment strategy using ruthenium metal complexes can be a new therapeutic approach for the efficient treatment of SCI.

2,3-Bis(2-pyridyl)thieno[3,4-b]pyrazine and its ruthenium(II) complexes: a new bidentate bridging ligand for enhanced metal-metal communication.

A new bidentate bridging ligand, bis(2-pyridyl)thieno[3,4-b]pyrazine is reported, along with its mono- and bi-metallic Ru(II) complexes as representative examples. Spectroscopic, electrochemical and X-ray crystallographic characterization of these species is reported, with the separation of the two Ru(III)/Ru(II) couples of the bimetallic complex suggesting better metal-metal communication than classical polypyridyl analogues.

Photoinduced Self-assembly: An Alternative Strategy for the Construction of Coordination Oligomers and Polymers.

Self-assembled oligonuclear and polynuclear complexes have numerous functionalities and potential applications. Generally, such compounds have been constructed by thermal substitution reactions with bridging ligands. Herein, we report bottom-up and photochemical construction of functional coordination oligomers and polymers by photosubstitution-induced self-assembly. The photosubstitution reactions of a ruthenium precursor complex with bridging ligands having pyrazole moieties afford mono-, di-, tri-, tetra-, and pentanuclear ruthenium complexes, Ru1-Ru5, which have one-dimensional architectures. Intramolecular hydrogen bonding between each bridging ligand is a key to construct the molecular nanowires. All the complexes have been isolated and thoroughly characterized. The photochemically synthesized ruthenium complexes act as synthons for longer metal-complex-based nanowires with a length of the order of tens-of nanometers. The multinuclear complexes are generated by photoinduced self-assembly in the presence of a base, and they undergo photoinduced disassembly in the presence of acid.

A synergetic effect of light and anion: near-infrared colorimetric monitoring of nitric oxide (NO) release from fluoride/cyanide anions and a water responsive ruthenium nitrosyl complex.

Near-infrared (NIR) spectral-responsive multitasking chemical systems are always advantageous in biological and environmental systems. Although ruthenium complexes are highly attractive compounds for many applications, studies on NIR optical responsive sensors are very limited because of their synthetic difficulties. The sensing of fluoride and cyanide ions using ruthenium nitrosyl complexes is not known. In this study, we report the synthesis and characterization of a new terpyridine-based ruthenium nitrosyl complex [Ru(Cl)2NO(terpy-C6H4OH)] 1·Ru-OH. The complex exhibited distinct NIR absorptions at 680 nm, as well as a visible color change with the fluoride ion in DMSO-CH3CN medium. However, when the solvent is changed to DMSO-H2O, it responds only with a cyanide ion with a distinct colorimetric change. Binding of the F- ion leads to deprotonation of 1·Ru-OH; the deprotonated complex is also used for the colorimetric detection of a trace amount of water in DMSO and acetonitrile with a limit of detection (LOD) of 0.034 wt% and 0.007 wt%, respectively. Ruthenium nitrosyl complexes have appeared as promising platforms for light-controlled release of nitric oxide (NO), which can be beneficial for therapeutic application. NO release studies of 1·Ru-OH by UV-vis and FT-IR spectroscopy confirm that it can release NO in a light-controlled manner. In addition, the NO release could be monitored by the naked eye with a color change and spectral change in the NIR region. Importantly, NO release studies revealed that the rate of NO release could be modulated in the presence of the F- ion. Here, the fluoride ion acts as an allosteric regulator. These results demonstrate that 1·Ru-OH is both a promising multitasking colorimetric and NIR sensor and a colorimetric responsive NO-releasing agent.

Application of enaminone ruthenium(II) complexes as catalysts in the transfer hydrogenation of ketones

This study reported the synthesis of two new ligands (1,2) and their Ru(II)-enaminone complexes (3,4). The Ru(II) complexes were obtained from the reaction of the [RuCl2(p-cymene)]2 dimers with the new enaminone derivative ligands (1,2). The use of standard spectroscopy techniques entirely characterized the compounds. Single crystal studies investigated the crystal structure of ligand (1) and complexes (3,4). X-ray diffraction data analysis was used to confirm the enaminone form of 1. Also, 3 and 4 exhibited the classical three-legged piano stool structure with Ru(II) coordinated by the nitrogen and oxygen atoms of 1 and a chloride ligand as the legs and the η6-π-bound p-cymene ligand occupies the seat of the piano stool. The Ru(II) complexes have been studied as catalysts in the transfer hydrogenation of acetophenone and other various ketones in the presence of KOtBu. The catalytic conditions were optimized using different substrate/catalyst and base/catalyst ratios. We found that the complexes show good activities and up to 100 % selectivity. The best turnover frequency (1667 h−1) was found for 3 when using acetophenone as the substrate.

AIE-based ruthenium complexes as photosensitizers for specifically photo-inactivate gram-positive bacteria

The emergence of multidrug-resistant bacterial have caused severe burden for public health. Particularly, Staphylococcus aureus as one of ESKAPE pathogens have induced various infectious diseases and resulted in increasing deaths. Developing new antibacterial agents is still urgent and challenging. Fortunately, in this study, based on aggregation-induced emission (AIE) ruthenium complexes were designed and synthesized, which realized the high efficiency of reactive oxygen species generation and remarkably killed S. aureus unlike conventional antibiotics action. Significantly, owing to good singlet oxygen production ability, Ru1 at only 4 μg/mL of concentration displayed good antibacterial photodynamic therapy effect upon white light irradiation and could deplete essential coenzyme NADH to disrupt intracellular redox balance. Also, the electrostatic interaction between Ru1 and bacteria enhanced the possibility of antibacterial. Under light irradiation, Ru1 could efficiently inhibit the biofilm growth and avoid the development of drug-resistant. Furthermore, Ru1 possessed excellent biocompatibility and displayed remarkable therapy effect in treating mice-wound infections in vivo. These findings indicated that AIE-based ruthenium complexes as new antibacterial agent had great potential in photodynamic therapy of bacteria and addressing the drug-resistance crisis.

Ruthenium complexes with abiraterone acetate as antiproliferative agents

This study is dedicated to the development of multimodal anticancer agents. We have obtained ruthenium complexes conjugated with the steroid-type antitumor drug abiraterone acetate in order to take advantage of the dual antitumor properties of both ruthenium and abiraterone. The compounds exhibit good antiproliferative activity against cancer cells, with selectivity over primary fibroblasts. Real-time cell analysis revealed that compound dichlorido(η66-p-cymene)(abiraterone acetate)ruthenium(II) had pronounced antiproliferation activity compared to abiraterone acetate. Flow cytometric studies on the mechanism of cell death have revealed that the most active compound induces apoptosis more effectively than abiraterone acetate. Our findings demonstrate the potential of this novel dual-action compound as promising candidates for further development as anticancer agents.

Asymmetric Transfer Hydrogenation of gem-Difluorocyclopropenyl Ketones: The Synthesis and Functionalization of Enantioenriched cis gem-Difluorocyclopropyl Ketones.

The asymmetric transfer hydrogenation of gem-difluorocyclopropenyl ketones, catalyzed by a Noyori-Ikariya ruthenium complex, was developed to access substituted optically enriched cis-disubstituted gem-difluorocyclopropyl ketones, and the value of these latter building blocks was illustrated by the synthesis of heterocycles fused to the difluorocyclopropyl moiety.

Functionalization of ionic liquids for heterogeneous catalysis in CO2 conversion: Cycloaddition of epoxides and hydrogenation

The mitigation of environmental impacts caused by greenhouse gas emissions has become increasingly urgent, and the use of CO2 as a primary carbon source is an alternative in chemical transformations, including the synthesis of organic carbonates, formic acid, or methanol. This work aims to synthesize ionic liquids from the imidazolium cation family to be used in the cycloaddition of CO2 with ILs anchored in SiO2-clay heterostructure, MCM-41 and KIT-6 mesoporous materials, as well as the hydrogenation of CO2 with ILs added to ruthenium complexes, i.e., two catalytic systems. The most satisfactory result for CO2 cycloaddition (TON PC = 226) was obtained using the IL (MeO)3Sipmim.Cl anchored in SiO2-clay heterostructure (0.16 mol%) as the catalyst and ZnBr2 (0.04 mol%) as the co-catalyst. The hydrogenation was conducted with the IL (edaO)3Sipmim.Cl and the ruthenium complex Ru-PNN were not successful, but with co-catalyst PEHA, formic acid/formamide was produced (TON Form = 552). The unique catalytic system that showed activity for forming methanol was the commercial Ru-MACHO, Ru-C29H30ClNOP2, (TON MeOH = 3.3). These results highlight the potential of ruthenium-based complexes and supported ionic liquids as active systems in CO2 conversion.

Stereoselective Synthesis of Chiral C2-Symmetric 1,3- and 1,5-Bis-Sulfoxides Guided by the Horeau Principle: Understanding the Influence of the Carbon Chain Nature in Its Ability for Metal Coordination.

The stereoselective synthesis of two distinct types of C2-symmetric chiral bis-sulfoxides, 1,3- and 1,5-bis(sulfinyl) derivatives, has been achieved based on the DAG methodology. The 1,5-bis(sulfinyl) derivatives constitute a new family of tridentate chiral ligands thanks to the presence of an additional sulfenyl or sulfinyl group in the carbon chain acting as a bridge. A systematic development and optimization of two synthetic routes, one for each ligand family, have been undertaken, highlighting the strategic utilization of Horeau's law to enhance enantioselectivity. Additionally, palladium (Pd) and ruthenium (Ru) complexes derived from the synthesized bis-sulfoxides were prepared, and their structures were elucidated through spectroscopic analysis. Isolation of Pd(II) complexes involving 1,3-bis-sulfoxides was exclusively achieved using trifluoroacetates as coligands. In the case of Ru(II) complexes, the trans geometry could be determined for 1,3-bis-sulfoxides. The introduction of a third sulfur atom as a coordinating element in the 1,5-bis(sulfinyl) derivatives facilitates the formation of two distinct tricoordinated Ru(II) complexes. The structure of these complexes is intricately influenced by the oxidation state adopted by the central sulfur on the chain, whether as a thioether or as a sulfoxide.

RUTHENIUM ORGANOMETALLIC COMPOUNDS IN CANCER TREATMENT

Organometallic complexes with ruthenium have shown promise as potential anticancer agents. These complexes represent a class of compounds that can exhibit unique mechanisms of action, and they may offer advantages or overcome some limitations associated with platinum-based drugs, such as cisplatin. Ruthenium-based complexes can have diverse mechanisms of action. They may interact with DNA, proteins, or other cellular components, leading to cytotoxic effects on cancer cells. The versatility of ruthenium coordination chemistry allows for the design of complexes with specific properties. Some cancers that become resistant to platinum-based drugs may still respond to ruthenium-based compounds. This reduced cross-resistance is attributed to differences in the mechanisms of action between platinum and ruthenium complexes. Researchers can design ruthenium complexes to target specific cellular pathways or processes associated with cancer. This targeted approach aims to enhance the selectivity of the treatment for cancer cells while minimizing the impact on normal cells. Ruthenium complexes often have unique structural features that contribute to their stability and reactivity. These features can be tailored to optimize the pharmacological properties of the compounds. Ruthenium-based complexes may be explored in combination with other anticancer agents to achieve synergistic effects and enhance overall treatment efficacy. Ongoing research continues to explore the potential of ruthenium-based organometallic complexes, and preclinical studies have demonstrated promising results. As with any emerging field, further investigations and clinical trials are needed to fully understand the therapeutic potential and safety profiles of these compounds for various types of cancers.

Synthesis and Evaluation of amyloid beta peptide/ Ruthenium III -based complex drugs as drug delivery and anticancer activity

The development and characterization of anticancer complex drugs (ACD), specifically Amyloid Beta Peptide (ABP) - Ruthenium III (Ru III) - nivolumab (NB), were explored through analytical techniques. Fourier-transform infrared (FTIR) spectroscopy demonstrated the structural transformation of peptides from α-helical to β-sheet formations, aligning with amyloid fibril aggregation. Ruthenium (III) complex synthesis was confirmed through distinct absorption peaks in FTIR analysis. High-resolution scanning electron microscopy (HRSEM) revealed the fibrous and smooth morphology of ACD, while thermogravimetric analysis (TGA) confirmed the decomposition stages and stability of the ruthenium complexes. The encapsulation efficiency and in vitro release profile of nivolumab (NB) within ABP-RuIII-NB were investigated, showing a two-phase release over 40h. Cytotoxicity studies using acridine orange and ethidium bromide staining techniques indicated significant apoptosis in human oral squamous cell carcinoma (OSCC) -treated cells. These findings highlight the potential of ABP-RuIII-NB as an effective cancer treatment with controlled drug release and high cytotoxicity against cancer cells.

Base-free transfer hydrogenation of carbonyl substrates catalysed by neutral ruthenium(salicylaldimine) complexes: Inhibitory effect of visible light

In this study, a series of neutral ruthenium salicylaldimine complexes were synthesized and evaluated as catalysts for the base-free transfer hydrogenation of carbonyl compounds, including acetophenone. Under base-free conditions, the complexes demonstrated high catalytic activity, achieving conversions of up to 79 % for acetophenone with a turnover number (TON) of 790 after 2 h at 82 °C. Comparatively, when a base (2 mol% KOH) was used, the conversion dropped to 17–25 %. Extending the reaction time to 3 h under base-free conditions increased the conversion to 90 %, with a TON of 900. The catalysts were also tested on a range of substrates: acetophenone derivatives with electron-donating substituents showed conversions up to 89 %, while electron-withdrawing groups resulted in lower conversions (67 %). Additionally, sterically hindered substrates like benzophenone yielded 72 % conversion. Visible light exposure significantly reduced catalytic activity, resulting in up to a 26 % decrease in conversion due to the formation of an inactive bis(salicylaldimine) ruthenium species. Mechanistic studies revealed that the reaction proceeds via an oxidative addition pathway, with the formation of a ruthenium-hydride intermediate confirmed by NMR and FT-IR spectroscopy.

Ruthenium(II) complexes containing PEGylated N-heterocyclic carbene ligands for tunning biocompatibility in the fight against cancer

A synthetic procedure was designed for the preparation and characterization of Ag and Ru complexes containing NHC ligands functionalized with PEG fragments. Stability studies were conducted to gain insight of the species in water and other solvents like DMSO, or with reagents like imidazole as representative group for histidine amino acid. The presence of Cl atoms instead of H in the 4,5 positions of the N-heterocyclic carbene afforded higher water stability. The complexes containing PEG units must be considered inactive as anticancer agents. To enhance the anticancer activity of PEG-containing complexes, the balance between hydrophilicity and hydrophobicity was adjusted using a silane moiety, and an anionic carbosilane dendrimer as a lipophilic carrier.

Hydrogen Production from Aqueous Formic Acid through the Ligand Design Strategy in Half-Sandwich Ruthenium Complexes

Hydrogen Production from Aqueous Formic Acid through the Ligand Design Strategy in Half-Sandwich Ruthenium Complexes

New Organoruthenium(II) Complexes Containing Andrographolide‐Appended Hydrazide Derivatives: Synthesis, Spectral Characterization, Anticancer Evaluation

ABSTRACTA new set of andrographolide‐appended hydrazide derivatives (AFC, AGC, and ATC) were prepared from the reaction of andrographolide with furan‐2‐carboxylic acid hydrazide (AFC), pyridine‐3‐carboxylic acid hydrazide (AGC), and thiophene 2‐carboxylic acid hydrazide (ATC), and their corresponding ruthenium(II) complexes (Ru‐AFC, Ru‐AGC, and Ru‐ATC) were synthesized by the direct reaction of [RuCl2(η6‐p‐cymene)]2 with ligands in dichloromethane under stirring condition. The compounds were analyzed by elemental analysis, IR, UV‐Vis, 1H NMR, and ESI‐MS spectrometric techniques, and the obtained spectral data revealed that the ligands coordinated to Ru(II) ion through their enone oxygen and amine nitrogen. Antioxidant activities of the ligands and complexes were calculated against DPPH•, ABTS•+, O2−, and NO• free radicals and their results were compared with standard antioxidants. The cytotoxic activity of the synthesized ligands and complexes toward A549 and HeLa cell lines was evaluated using MTT method (MTT = 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide). Among the compounds, the complex Ru‐AGC showed better cytotoxic effect against A549 and HeLa cancer cells with IC50 values of 4.75 ± 0.17 and 6.32 ± 0.26 μM, respectively. Further, the nontoxic nature of the compounds was confirmed by using human umbilical vein endothelial (HUVEC) cells. The apoptosis was inspected with AO/EB and DAPI staining methods; further, the percentages of the apoptotic and necrotic cells were determined by flow cytometry. Overall, the biological activities of our ruthenium(II)‐arene complexes were found to be more potent than their parent ligands due to chelation, and among the complexes, Ru‐AGC showed better activity due to the presence of pyridine ring in the N‐terminal position of the ligand. The obtained results highlighted the strong possibility to develop highly active ruthenium complexes as anticancer agents.

Ruthenium Catalyzed Formation of Fused Pyridine Derivatives or Substituted Indoles from Hydrazine‐Derived Enamines and Propargyl Alcohols

New ruthenium‐catalyzed transformations of secondary propargyl alcohols with hydrazine‐derived enamines are presented, affording fused pyridines or substituted indoles depending on the hydrazine derivative used. The cascade reactions are catalyzed by an air‐ and moisture‐stable bifunctional ruthenium complex and proceed via redox‐isomerization of the propargyl alcohol, subsequent Michael addition and cyclocondensation. In case of phenylhydrazine a Fischer‐indole synthesis also takes place, prior to the final release of the products. The produced heterocyclic motifs are important scaffolds in medicinal and agricultural chemistry.

Effect of solution environment on the binding properties of ruthenium(II) complexes [Ru(bim)2(7-CH3-dppz)]2+ and [Ru(bim)2(dppx)]2+ with double-stranded RNA poly(A)·poly(U)

Two new ruthenium(Ⅱ) complexes containing the same ancillary ligands and different intercalating ligands, [Ru(bim)2(7-CH3-dppz)]2+ (Ru1, bim = 2,2′-biimidazole, 7-CH3-dppz = 7-methyl-dipyrido-[3,2-a,2′,3′-c]-phenazine) and [Ru(bim)2(dppx)]2+ (Ru2, dppx = 7,8-dimethyldipyridophenazine), have been synthesized and characterized in this work, and the interactions of Ru1 and Ru2 with double-stranded RNA poly(A)·poly(U) have been comparatively studied under both dilute and molecular crowding conditions. Analysis of spectral titrations and viscosity experiments as well as thermal denaturation experiments suggests that although complexes Ru1 and Ru2 in both dilute and molecular crowding solutions bind to poly(A)·poly(U) via intercalation, while the binding and stabilizing effects of the two complexes toward poly(A)·poly(U) under molecular crowding conditions significantly decreases in comparision with those in dilute solutions, suggesting that molecular crowding has a significant weakening effect on the interaction of the two complexes with poly(A)-poly(U). The results obtained will contribute to the understanding of the effects of molecular crowding conditions on the binding and stabilization of double-stranded RNA by metal complexes, in particular Ru(II) complexes.