Unique Optical Oxygen-Sensing Performance of [Ru(IP)2(HNAIP)]2+ during the Groove-Binding-Induced B-to-Z DNA Conformational Transition

Naphthalene Diimide and Bis-Heteroleptic Ru(II) Complex-Based Hybrid Molecule with 3-in-1 Functionalities

Multipurpose applications of a newly developed homobimetallic Ru(II) complex, Ru-NDI[PF6]4, which incorporates 1,10-phenanthroline and triazole-pyridine ligands and linked via a (-CH2-)3 spacer to the reputed anion-π interacting NDI system, are described. Solution-state studies of the bimetallic complex, including EPR, PL, UV-vis, and NMR experiments, reveal two sequential one-electron transfers to the NDI unit, generating NDI⋅- and NDI2- in the presence of F- selectively. This process inhibits the primary electron transfer from Ru(II) to the NDI unit, thereby allowing the 3MLCT-based emission of the complex to be recovered, resulting in a corresponding ten-fold increase in luminescence intensity. DFT and TD-DFT computational studies further elucidate the experimentally observed absorption spectra of the complex. Secondly, CT-DNA binding studies with the complex are performed using various spectroscopic analyses such as UV-vis, PL, and CD. Comparative DNA binding studies employing EB and molecular docking reveal that the binding with CT-DNA occurs through both intercalative and groove binding modalities. Thirdly, the photocatalytic activities of the complex towards C-C, C-N, and C-O bond formation in organic cross-coupling reactions, including the amidation of α-keto acids to amines and the oxidation of alcohol to aldehydes, are also demonstrated.

Fine-tuning the cytotoxicity of ruthenium(II) arene compounds to enhance selectivity against breast cancers

Ruthenium-based complexes have been suggested as promising anticancer drugs exhibiting reduced general toxicity compared to platinum-based drugs. In particular, Ru(η6-arene)(PTA)Cl2 (PTA = 1,3,5-triaza-7-phosphaadamantane), or RAPTA, complexes have demonstrated efficacy against breast cancer by suppressing metastasis, tumorigenicity, and inhibiting the replication of the human tumor suppressor gene BRCA1. However, RAPTA compounds have limited cytotoxicity, and therefore comparatively high doses are required. This study explores the activity of a series of RAPTA-like ruthenium(II) arene compounds against MCF-7 and MDA-MB-231 breast cancer cell lines and [Ru(η6-toluene)(PPh3)2Cl]+ was identified as a promising candidate. Notably, [Ru(η6-toluene)(PPh3)2Cl]Cl was found to be remarkably stable and highly cytotoxic, and selective to breast cancer cells. The minor groove of DNA was identified as a relevant target.

Anticancer and antibacterial potential of robust Ruthenium(II) arene complexes regulated by choice of α-diimine and halide ligands

Several complexes of general formula [Ru(halide)(η⁶-p-cymene)(α-diimine)]⁺, in the form of nitrate, triflate and hexafluorophosphate salts, including a newly synthesized iodide compound, were investigated as potential anticancer drugs and bactericides. NMR and UV-Vis studies evidenced remarkable stability of the complexes in water and cell culture medium. In general, the complexes displayed strong cytotoxicity against A2780 and A549 cancer cell lines with IC₅₀ values in the low micromolar range, and one complex (RUCYN) emerged as the most promising one, with a significant selectivity compared to the non-cancerous HEK293 cell line. A variable affinity of the complexes for BSA and DNA binding was ascertained by spectrophotometry/fluorimetry, circular dichroism, electrophoresis and viscometry. The performance of RUCYN appears associated to enhanced cell internalization, favored by two cyclohexyl substituents, rather than to specific interaction with the evaluated biomolecules. The chloride/iodide replacement, in one case, led to increased cellular uptake and cytotoxicity at the expense of selectivity, and tuned DNA binding towards intercalation. Complexes with iodide or a valproate bioactive fragment exhibited the best antimicrobial profiles.

DNA interaction of ruthenium(ii) complexes with imidazo[4,5-f][1,10]phenanthroline derivatives

The DNA interaction properties of four Ru(ii) complexes with imidazo[4,5-f][1,10]phenanthroline derivatives were investigated by spectral titration, gel electrophoresis (GAR), dynamic light scattering (DLS), zeta potential, atomic force microscopy (AFM), and transmission electron microscopy (TEM).

Interfering with DNA High-Order Structures using Chiral Ruthenium(II) Complexes

In this work, it was found that DNA can undergo B-Z transformational changes and compaction in the presence of DNA intercalators such as ruthenium(II) polypyridyl complexes. The link between B-Z transition and condensation is weak but can be strengthened under certain circumstances with slight alterations to the structures of the ruthenium(II) complexes. Here, following on from previous research, this work reports a series of ruthenium(II) complexes with imidazophenanthroline ligands, which vary in size and planarity. The complexes exhibit distinct effects on DNA structures, ranging from little impact to the transformation of DNA secondary structures to the formation of higher-order DNA structures. Further studies on DNA morphological changes induced by chiral ruthenium(II) complexes are observed by atomic force microscopy and transmission electron microscopy.

Molecular Basis for Differential Recognition of G-Quadruplex versus Double-Helix DNA by Bis-Phenanthroline Metal Complexes

1,10-Phenanthroline (Phen) derivatives are attractive ligands to provide metal complexes that are selective for different DNA secondary structures. Herein, we analyze the binding processes of two bis-Phen analogues and their Ni(II) complexes toward double-stranded DNA and telomeric G-quadruplex DNA by calorimetric and spectroscopic techniques. The free ligands can adapt to both DNA arrangements. Conversely, metal ion coordination produces an increase in ligand affinity for the tetrahelical structure, whereas it dramatically decreases binding to double-stranded DNA as a result of distinct binding modes on the two templates. In fact, Ni(II) complexes effectively stack on the G-quadruplex terminals, with an entropic loss counterbalanced by favorable enthalpy changes, whereas they cause a conformational reshaping of the double-helix form with a substantial decrease in the binding free energy. Consistently, no Ni(II) -DNA ionic pair has ever been identified. These results provide a rationale for the selective recognition of distinct DNA arrangements in view of targeted pharmacological applications.