Synthesis, crystal structure and cytotoxic activity of ruthenium(II) piano-stool complex with N,N-chelating ligand

Synthesis, Characterization and Biological Investigations of Half-Sandwich Ruthenium(II) Complexes Containing Benzimidazole Moiety

Half-sandwich Ru(II) complexes belong to group of biologically active metallo-compounds with promising antimicrobial and anticancer activity. Herein, we report the synthesis and characterization of arene ruthenium complexes containing benzimidazole moiety, namely, [(η⁶-p-cymene)RuCl(bimCOO)] (1) and [(η⁶-p-cymene)RuCl₂(bim)] (2) (where bimCOO = benzimidazole-2-carboxylate and bim = 1-H-benzimidazole). The compounds were characterized by ¹H NMR, ¹³C NMR, IR, UV-vis and CV. Molecular structures of the complexes were determined by SC-XRD analysis, and the results indicated the presence of a pseudo-tetrahedral (piano stool) geometry. Interactions in the crystals of the Ru complexes using the Hirshfeld surface analysis were also examined. In addition, the biological studies of the complexes, such as antimicrobial assays (against planktonic and adherent microbes), cytotoxicity and lipophilicity, were performed. Antibacterial activity of the complexes was evaluated against S. aureus, E. coli, P. aeruginosa PAO1 and LES B58. Cytotoxic activity was tested against primary human fibroblasts and adenocarcinoma human alveolar basal epithelial cells. Obtained biological results show that the ruthenium compounds have bacteriostatic activity toward Pseudomonas aeruginosa PAO1 strain and are not toxic to normal cells. A molecular docking study was applied as a predictive source of information about the plausibility of examined structures binding with HSA as a transporting system.

Anticancer half-sandwich Ir(iii) complex and its interaction with various biomolecules and their mixtures – a case study with ascorbic acid

An anticancer azo bond-containing half-sandwich Ir(iii) complex oxidizes ascorbate to dehydroascorbate, and ascorbate recovers in the presence of reduced glutathione.

Ruthenium Complexes with 2-Pyridin-2-yl-1H-benzimidazole as Potential Antimicrobial Agents: Correlation between Chemical Properties and Anti-Biofilm Effects

Antimicrobial resistance is a growing public health concern that requires urgent action. Biofilm-associated resistance to antimicrobials begins at the attachment phase and increases as the biofilms maturate. Hence, interrupting the initial binding process of bacteria to surfaces is essential to effectively prevent biofilm-associated problems. Herein, we have evaluated the antibacterial and anti-biofilm activities of three ruthenium complexes in different oxidation states with 2-pyridin-2-yl-1H-benzimidazole (L1 = 2,2'-PyBIm): [(η6-p-cymene)RuIIClL1]PF6 (Ru(II) complex), mer-[RuIIICl3(CH3CN)L1]·L1·3H2O (Ru(III) complex), (H2L1)2[RuIIICl4(CH3CN)2]2[RuIVCl4(CH3CN)2]·2Cl·6H2O (Ru(III/IV) complex). The biological activity of the compounds was screened against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa strains. The results indicated that the anti-biofilm activity of the Ru complexes at concentration of 1 mM was better than that of the ligand alone against the P. aeruginosa PAO1. It means that ligand, in combination with ruthenium ion, shows a synergistic effect. The effect of the Ru complexes on cell surface properties was determined by the contact angle and zeta potential values. The electric and physical properties of the microbial surface are useful tools for the examined aggregation phenomenon and disruption of the adhesion. Considering that intermolecular interactions are important and largely define the functions of compounds, we examined interactions in the crystals of the Ru complexes using the Hirshfeld surface analysis.

Synthesis and Structure of Novel Copper(II) Complexes with N,O- or N,N-Donors as Radical Scavengers and a Functional Model of the Active Sites in Metalloenzymes

To evaluate the antioxidant activity of potential synthetic enzyme mimetics, we prepared new five copper(II) complexes via a self-assembly method and named them [Cu(2-(HOCH₂)py)₃](ClO₄)₂ (1), [Cu(2-(HOCH₂)py)₂(H₂O)₂]SiF₆ (2), [Cu₂(2-(HOCH₂CH₂)py)₂(2-(OCH₂CH₂)py)₂](ClO₄)₂ (3), [Cu(pyBIm)₃](BF₄)₂·1.5H₂O (4) and [Cu(py₂C(OH)₂)₂](ClO₄)₂ (5). The synthetic protocol involved N,O- or N,N-donors: 2-(hydroxymethyl)pyridine (2-(HOCH₂)py), 2-(hydroxyethyl)pyridine (2-(HOCH₂CH₂)py), 2-(2-pyridyl)benzimidazole (pyBIm), di(2-pyridyl)ketone (py₂CO). The obtained Cu(II) complexes were fully characterised by elemental analysis, FTIR, EPR, UV-Vis, single-crystal X-ray diffraction and Hirshfeld surface analysis. Crystallographic and spectroscopic analyses confirmed chromophores of both monomeric ({CuN₃O₃} (1), {CuN₂O₄} (2), {CuN₆} (4), {CuN₄O₂} (5)) and dimeric complex ({CuN₂O₃} (3)). Most of the obtained species possessed a distorted octahedral environment, except dimer 3, which consisted of two copper centres with square pyramidal geometries. The water-soluble compounds (1, 3 and 5) were selected for biological testing. The results of the study revealed that complex 1 in solutions displayed better radical scavenging activity than complexes 3, 5 and free ligands. Therefore, complex 1 has been selected for further studies to test its activity as an enzyme mimetic. The chosen compound was tested on the erythrocyte lysate of two groups of patients after undergoing chemotherapy and chemoradiotherapy. The effect of the tested compound (1) on enzyme activity levels (TAS, SOD and CAT) suggests that the selected complex can be treated as a functional mimetic of the enzymes.

Ruthenium(II) and Iridium(III) Complexes as Tested Materials for New Anticancer Agents

The oncological use of cisplatin is hindered by its severe side effects and a very important resistance problem. To overcome these problems, scientists have attempted to design new generation transition-metal anticancer complexes. In this study, we present new complexes, ruthenium(II) [(η6-p-cymene)RuCl(py2CO)]PF6 (1), iridium(III) [(η5-Cp)IrCl(py2CO)]PF6 (2), and NH4[IrCl4(py2CO)]·H2O (3), based on di-2-pyridylketone (py2CO). The prepared complexes were characterized by FTIR, 1H, 13C, 15N NMR, UV-Vis, PL and elemental analysis techniques. The single-crystal X-ray structure analysis and comparative data revealed pseudo-octahedral half-sandwich 1 and 2 complexes and octahedral tetrachloroiridate(III) 3 with a rare chelating κ2N,O coordination mode of py2CO. The compounds were tested in vitro against three cancer cell lines-colorectal adenoma (LoVo), myelomonocytic leukaemia (MV-4-11), breast adenocarcinoma (MCF-7), and normal fibroblasts (BALB/3T3). The most promising results were obtained for iridium(III) complex 3 against MV-4-11 (IC50 = 35.8 ± 13.9 µg/mL) without a toxic effect against normal BALB/3T3, which pointed towards its selectivity as a potential anticancer agent. Extensive research into their mode of binding with DNA confirmed for 1 and 2 complexes non-classical binding modes, while the 3D circular dichroism (CD) experiment (ΔTm) suggested that 3 induced the probable formation of covalent bonds with DNA. In addition, the obtained iridium complexes induce ROS, which, in synergy with hydrolysis promoting DNA bonding, may lead to cancer cell death.

Synthesis and antiproliferative activity of benzimidazole-based, trinuclear neutral cyclometallated and cationic, N^N-chelated ruthenium(ii) complexes

A series of 2-phenyl and 2-pyridyl tris-benzimidazole ligands was reacted with the [Ru(p-cymene)Cl₂]₂ dimer to yield the corresponding neutral cyclometallated and cationic trinuclear organoruthenium(ii) complexes.

Similarities and differences in d6 low-spin ruthenium, rhodium and iridium half-sandwich complexes: synthesis, structure, cytotoxicity and interaction with biological targets

In this paper, we discussed the similarities and differences in d⁶ low-spin half-sandwich ruthenium, rhodium and iridium complexes containing 2,2′-biimidazole (H₂biim). Three new complexes, {[RuCl(H₂biim)(η⁶-p-cymene)]PF₆}₂·H₂O (1), [(η⁵-Cp)RhCl(H₂biim)]PF₆ (2), and [(η⁵-Cp)IrCl(H₂biim)]PF₆ (3), were fully characterized by CHN, X-ray diffraction analysis, UV–Vis, FTIR, and ¹H, ¹³C and ¹⁵N NMR spectroscopies. The complexes exhibit a typical pseudooctahedral piano-stool geometry, in which the aromatic arene ring (p-cymene or Cp) forms the seat, while the bidentate 2,2′-biimidazole and chloride ion form the three legs of the piano stool. Moreover, the cytotoxic activities of the compounds were examined in the LoVo, HL-60, MV-4-11, MCF-7 human cancer cell lines and BALB/3T3 normal mouse fibroblasts. Notably, the investigated complexes showed no cytotoxic effects towards the normal BALB/3T3 cell line compared to cisplatin, which has an IC₅₀ value of 2.20 µg. Importantly, 1 displayed the highest activity against HL-60 (IC₅₀ 4.35 µg). To predict a binding mode, we explored the potential interactions of the metal complexes with CT-DNA and protein using UV absorption and circular dichroism. The obtained data suggest that the complexes could interact with CT-DNA via an outside binding mode. Moreover, binding of the complexes with the GSH via UV–Vis and ESI mass spectra was determined. Comparative studies have shown that the rhodium complex (2) is the most GSH reactive, which is probably responsible for its deactivation towards LoVo and MCF-7 tumour cells. The influence of the metal ion on the biological activity of isostructural Rh(III) and Ir(III) complexes was an important goal of the presented investigation.

Anticancer and antimicrobial properties of novel η6-p-cymene ruthenium(ii) complexes containing a N,S-type ligand, their structural and theoretical characterization

Ruthenium(ii) complexes are lately of great scientific interest due to their chemotherapeutic potential as anticancer and antimicrobial agents. Here we present the synthesis of new pyrazole carbothioamide derivatives and their four arene–ruthenium complexes. The title compounds were characterized with the application of IR, NMR, mass spectrometry, elemental analysis and X-ray diffraction. Additionally, for new complexes DFT calculations were done. Their antimicrobial activity (MIC, MBC/MFC) was examined in vitro against Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Pseudomonas aeruginosa, Proteus vulgaris and Candida albicans. Their cytotoxic effects, using the MTT assay, against three cancer cell lines: HL-60, NALM-6, WM-115 and normal human foreskin fibroblasts (HFF-1) were also investigated. The influence of the new arene–ruthenium(ii) complexes on the DNA structure was also tested. From our results, compound 2d showed higher cytotoxicity against melanoma cell line WM-115 than cisplatin. Strong biostatic and biocidal activity of the tested complexes against Gram-positive bacteria, including S. aureus, S. epidermidis and E. faecalis was demonstrated. The new arene–ruthenium(ii) compounds could not only inhibit proliferation of cancer cells, but also protect patients against malignant wound infections.

New arene–ruthenium(ii) complexes with pyrazole derivatives as ligands were synthesized and characterized. This compounds exhibited good cytotoxic effects, and strong biostatic and biocidal activity.

Recurrent supramolecular motifs in discrete complexes and coordination polymers based on mercury halides: prevalence of chelate ring stacking and substituent effects

We report the synthesis, X-ray characterization and DFT study of five Hg(ii) complexes with Schiff bases containing a nicotinohydrazide core to explore the formation of chelate-ring π-stacking interactions.