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

Fe(III) and Ni(II) imidazole-benzimidazole mixed-ligand complexes: synthesis, structural characterization, molecular docking, DFT studies, and evaluation of antimicrobial and anti-inflammatory activities

This work delves into the synthesis, characterization, and bioactivity of new metal complexes of imidazole (IM)-based and benzimidazole (BZ)-based ligands with Fe(III) and Ni(II) ions. Broad characterization techniques, including elemental analysis, IR spectroscopy, magnetic moment measurement, electronic spectral analysis, mass spectrometry, thermal analysis, and DFT calculations, confirmed the successful preparation of the complexes with a 1 : 1 : 1 (M : IM : BZ) stoichiometry. The NiBZI M and FeBZIM complexes possessed octahedral geometry, with one and two water molecules coordinated with Fe(III) and Ni(II), respectively. DFT calculations demonstrated that the reduction of the energy gap and increase in softness for the metal complexes resulted from metal coordination, enhancing the reactivity and biological activity of the complexes. The FeBZIM and NiBZIM complexes exhibited strong antimicrobial activity, with both complexes displaying improved efficacy towards Gram-positive and Gram-negative bacteria compared with their corresponding free ligands. Their activities were comparable to the standard antibiotic chloramphenicol. Furthermore, these complexes exhibited good antifungal activity towards Aspergillus niger and Candida albicans, surpassing that of the free ligands. MIC values also ensured enhanced antimicrobial activity of the metal complexes. Other than these properties, the complexes demonstrated significant anti-inflammatory activity, where the FeBZIM complex exhibited the highest activity, with an IC50 value closer to that of the reference drug. Molecular docking studies on the E. coli FabH-CoA complex (PDB ID: 1HNJ) and human cyclooxygenase-2 (COX-2) (PDB ID: 5IKT) revealed that the FeBZIM complex exhibited the highest binding affinity with the formation of several hydrogen bonds with key amino acid residues, suggesting a favorable antibacterial activity. Overall, the newly synthesized FeBZIM and NiBZIM complexes demonstrated immense potential as novel antimicrobial and anti-inflammatory drugs with enhanced efficacy compared with their free ligands.

Novel organoruthenium complexes containing β-Diketonates: Synthesis, characterization, DNA/HSA interactions, and the impact of biocompatible ionic liquids on biological activities

In order to discover new dual-active agents, novel ruthenium (η6-p-cymene) complexes of the general formula [(η6-p-cym)Ru(OO)Cl] with O,O-diketo ester ligands ethyl 2-hydroxy-4-aryl-4-oxobut-2-enoate (1-3), were synthesized. The complexes 1-3 were characterized by spectral techniques (UV-Vis, IR, 1H and 13C NMR, and ESI-HRMS), elemental analysis, and X-ray crystallography. Based on in vitro DNA/HSA experiments, complex 1 exhibited the highest DNA/HSA-activity, suggesting that the presence of an alkene chain contributes to increased activity. The cytotoxic activity of 1-3 was evaluated in a panel of human cancer cell lines (A549, MDA-MB-231, LS-174, HeLa), and in one normal cell line (MRC-5), both in the absence and presence of biocompatible ionic liquids (BIO-ILs) such as cholinium glycinate (Cho-Gly), cholinium β-alaninate (Cho-Ala), and cholinium glutamate (Cho-Glu). Complex 1 exhibited the highest cytotoxicity and demonstrated selectivity toward HeLa cells. Additionally, its cytotoxicity was enhanced when combined with the BIO-ILs Cho-Gly and Cho-Ala. This study suggests that ionic liquids can influence the efficacy and selectivity of cancer treatments, highlighting the potential for enhancing therapeutic outcomes. However, it also emphasizes the need for a deeper understanding of BIO-IL interactions with cellular processes. Furthermore, compound 1 displayed strong antimicrobial activity against Staphylococcus aureus and Escherichia coli (MIC = 0.078 mg/mL). Among the assessed species, Candida albicans showed the highest sensitivity to antifungal activity. These results suggest that investigated compounds may have potential for further development as clinical candidates, pending additional studies.

Ruthenium Complexes with Pyridazine Carboxylic Acid: Synthesis, Characterization, and Anti-Biofilm Activity

As a result of drug resistance, many antimicrobial medicines become ineffective, making the infections more difficult to treat. Therefore, there is a need to develop new compounds with antibacterial activity. This role may be played, for example, by metal complexes with carboxylic acids. This study reports the formation and characterization of ruthenium complexes with pyridazine-3-carboxylic acid (pdz-3-COOH)-([(η6-p-cym)RuIICl(pdz-3-COO)] (1), [RuIIICl2(pdz-3-COO)2Na(H2O)]n(H2O)0.11 (2) and [RuIIICl2(pdz-3-COO)2Na(H2O)2]n (3). The synthesized compounds were analyzed using various spectroscopic and electrochemical techniques, with structure confirmation via SC-XRD analysis. Experimental data showed the ligand binds to metal ions bidentately through the nitrogen donor of the pyridazine ring and one carboxylate oxygen. To visualize intermolecular interactions, Hirshfeld surface analysis and 2D fingerprint plots were conducted. Furthermore, the impact of ruthenium compounds (1 and 2) on the planktonic growth of selected bacterial strains and the formation of Pseudomonas aeruginosa PAO1 biofilm was examined. Both complexes demonstrated comparable anti-biofilm activity and outperformed the free ligand. The effect of the complexes on selected virulence factors of P. aeruginosa PAO1 was also investigated. Compounds 1 and 2 show high suppressive activity in pyoverdine production, indicating that the virulence of the strain has been reduced. This inhibitory effect is similar to the inhibitory effect of ciprofloxacin. Within this context, the complexes exhibit promising antibacterial activities. Importantly, the compounds showed no cytotoxic effects on normal CHO-K1 cells. Additionally, a molecular docking approach and fluorescence spectroscopy were used to determine the interactions of ruthenium complexes with human serum albumin.

Molecular insight into the structural and functional aspects of arene Ru(II) complexes bearing bulky thiourea ligands

Herein we report four new arene ruthenium(II) complexes [RuII(η6-p-cymene)(L1)к1(S)Cl2] (C1), [RuII(η6-benzene)(L1)к1(S)Cl2] (C2) where L1 is N-((2,6-dimethylphenyl)carbamothioyl)benzamide (L1), and [RuII(η6-p-cymene)(L2)к1(S)Cl2] (C3), [RuII(η6-benzene)(L2)к1(S)Cl2] (C4) where L2 is N-((2,6-diisopropylphenyl)carbamothioyl)benzamide (L2) which were synthesized and evaluated for biological activity. The monodentate coordination of thione sulphur (S) to ruthenium ion along with two terminal chloride was confirmed by X-Ray diffraction analysis thus revealing a typical "piano-stool" pseudo tetrahedral geometry. DPPH radical scavenging activity showed that ligands were less efficient however on complex formation it showed significant efficacy with C4 showing the highest activity. The ligands and ruthenium complexes exhibited minimal to no cytotoxic effects on HEK cells within the concentration range of 10-300 μM. Evaluating the cytotoxicity against prostate cancer cells (DU145) L1, L2 and C1 displayed more pronounced cytotoxic activity with C1 showing high cytotoxicity against the cancer cells, in comparison to cisplatin indicating its potential for further investigation and analysis. Considering this, compound C1 was used to further study its interaction with BSA using fluorescence spectroscopy and it was found to be 2.64 × 106 M-1. Findings from CD spectroscopy indicate the binding in the helix region which was further confirmed with the molecular docking studies.

A review on metal complexes and its anti-cancer activities: Recent updates from in vivo studies

Research into cancer therapeutics has uncovered various potential medications based on metal-containing scaffolds after the discovery and clinical applications of cisplatin as an anti-cancer agent. This has resulted in many metallodrugs that can be put into medical applications. These metallodrugs have a wider variety of functions and mechanisms of action than pure organic molecules. Although platinum-based medicines are very efficient anti-cancer agents, they are often accompanied by significant side effects and toxicity and are limited by resistance. Some of the most studied and developed alternatives to platinum-based anti-cancer medications include metallodrugs based on ruthenium, gold, copper, iridium, and osmium, which showed effectiveness against many cancer cell lines. These metal-based medicines represent an exciting new category of potential cancer treatments and sparked a renewed interest in the search for effective anti-cancer therapies. Despite the widespread development of metal complexes touted as powerful and promising in vitro anti-cancer therapeutics, only a small percentage of these compounds have shown their worth in vivo models. Metallodrugs, which are more effective and less toxic than platinum-based drugs and can treat drug-resistant cancer cells, are the focus of this review. Here, we highlighted some of the most recently developed Pt, Ru, Au, Cu, Ir, and Os complexes that have shown significant in vivo antitumor properties between 2017 and 2023.