Search Results (12)

A set of new coordination compounds of the formula [RuNO(L)Cl₃], with L representing the bidentate ligands bipyrimidine (bpym), bipyridine (bpy), or phenanthroline (phen), was prepared and fully characterized. For the isomeric species fac-[RuNO(bpym)Cl₃] (1), fac-[RuNO(phen)Cl₃] (2), mer-[RuNO(phen)Cl₃] (3), fac-[RuNO(bpy)Cl₃] (4), and mer-[RuNO(bpy)Cl₃] (5), an evaluation of the photoresponse in DMSO was performed under excitation with 450 nm using a continuous-flow arrangement that enabled the simultaneous acquisition of IR and UV-Vis spectral data. Quantum yields for photoinduced release of NO were determined as follows: 5.4 ± 0.5% for fac-[RuNO(bpym)Cl₃] (1); 0.8 ± 0.1% for fac-[RuNO(phen)Cl₃] (2); 0.6 ± 0.1% for mer-[RuNO(phen)Cl₃] (3); 3.7 ± 0.1% for fac-[RuNO(bpy)Cl₃] (4); 2.1 ± 0.1% for mer-[RuNO(bpy)Cl₃] (5). The product of the photolysis of compound 5 in acetonitrile solution was isolated and structurally characterized as mer-[Ru(CH₃CN)(bpy)Cl₃] (6). Taking into account the presence of typical DNA intercalating ligands, the complexes can be potentially exploited as photoNORMs. Full article

Photo-induced bond linkage isomerization (BLI) in metal–nitrosyl compounds provides a molecular mechanism for controlling light-induced changes in refractive index and phase modulation. In this study, the ground and metastable states of a series of Ru–NO complexes and their Au₂₀, Ag₂₀, and mixed Au₁₀Ag₁₀ nanocluster hybrids were investigated by DFT and TDDFT calculations. The photochemical rearrangement between the linear, side-on, and O-bound forms of Ru–NO was examined together with their electronic transitions, oscillator strengths, and characteristic vibrational shifts. From these data, parameters describing radiative efficiency, non-radiative coupling, and metastable-state stability were derived to identify compounds with favorable properties for holography and photonic applications. Particular attention was given to the [(Salen)Ru(NO)(HS)@Au₂₀] complex, which shows a strong red-to-NIR response and balanced stability among its linkage isomers. Frequency-dependent polarizabilities α(ω) were calculated for its ground and metastable states and compared with those of the classical holographic material [Fe(CN)₅NO]²⁻ (nitroprusside). The refractive-index changes derived from α(ω) reveal that the Au₂₀–salen hybrid produces a much larger and more strongly wavelength-dependent Δn(λ) than nitroprusside. At 635 nm, the modulation reaches approximately 0.06 for the hybrid, compared with 0.02 for nitroprusside. This enhancement reflects the cooperative effect of the Ru–NO chromophore and the Au₂₀ nanocluster, which amplifies both polarizability and optical dispersion. The results demonstrate that coupling molecular photo-linkage isomerism with nanoplasmonic environments can significantly improve the performance of molecular systems for holography and optical-phase applications. Full article

Photoactivatable nitric oxide donors (photoNORMs) are promising agents for controlled NO release and real-time optical tracking in biomedical theranostics. Here, we report a comprehensive density functional theory (DFT) and time-dependent DFT (TDDFT) study on a series of hybrid ruthenium–gold nanocluster systems of the general formula [(L)Ru(NO)(SH)@Au₂₀], where L = salen, bpb, porphyrin, or phthalocyanine. Structural and bonding analyses reveal that the Ru–NO bond maintains a formal {RuNO}⁶ configuration with pronounced Ru → π*(NO) backbonding, leading to partial reduction of the NO ligand and an elongated N–O bond. Natural Bond Orbital (NBO), Natural Energy Decomposition Analysis (NEDA), and Extended Transition State–Natural Orbitals for Chemical Valence (ETS–NOCV) analyses confirm that Ru–NO bonding is dominated by charge-transfer and polarization components, while Ru–S and Au–S linkages exhibit a delocalized, donor–acceptor character coupling the molecular chromophore with the metallic cluster. TDDFT results reproduce visible–near-infrared (NIR) absorption features arising from mixed metal-to-ligand and cluster-mediated charge-transfer transitions. The calculated zero–zero transition and reorganization energies predict NIR-II emission (1.8–3.8 μm), a region of high biomedical transparency, making these systems ideal candidates for luminescence-based NO sensing and therapy. This study establishes fundamental design principles for next-generation Ru-based photoNORMs integrated with plasmonic gold nanoclusters, highlighting their potential as multifunctional, optically trackable theranostic platforms. Full article

Allergic asthma is characterized by chronic airway inflammation and recurrent bronchial hyperreactivity, highlighting the need for rapid therapeutic interventions during acute crises. This study aimed to assess the potential of a single-dose administration of the ruthenium nitrosyl complex cis-[Ru(bpy)₂(2-MIM)(NO)](PG₆)₃ (named as FOR811A) as a fast-acting treatment in a murine model of allergic asthma. Female Swiss mice were sensitized with ovalbumin for the induction of asthma and subjected to inhalation challenges. The experimental groups included controls and ovalbumin-sensitized mice receiving FOR811A (0.75 mg/kg) or saline (NaCl 0.9%), both by gavage. Lung tissues were collected for analyses of oxidative damage (nitrite/nitrate and GSH), inflammatory markers (myeloperoxidase, IL-1β, and IL-4), and histological assessment. The results showed that, while FOR811A did not significantly reduce oxidative damage or overall inflammation, it effectively decreased IL-4 levels, indicating a modulation of the Th2 immune response without affecting IL-1β levels (Th1 response). These findings suggest that a single-dose administration of FOR811A may provide a rapid therapeutic effect in allergic asthma crises by promoting smooth muscle relaxation and modulating immune responses. Further research is warranted to explore its clinical utility as a fast-acting rescue medication for acute asthma management. Full article

The reaction of [RuNO(Py)₂Cl₂OH] with bipyridine in water–ethanol media results in trans-(NO, OH)-[RuNO(Py)(Bpy)ClOH]⁺ with an acceptable yield (60–70%) as hexafluorophosphate salt. Further treatment of the hydroxy-complex with concentrated HF quantitatively leads to trans-(NO, F)-[RuNO(Py)(Bpy)ClF]⁺. Despite the chirality of both coordination spheres, the hexafluorophosphate salts crystallized as racemates. A NO-linkage isomerism study of the obtained complexes was performed at 80 K with different excitation wavelengths (405, 450, 488 nm). The most favorable wavelengths for the MS1 isomer (Ru-ON) formation were 405 and 450 nm, where the linkage isomer populations were 17% and 1% for [RuNO(Py)(Bpy)ClOH]PF₆ and [RuNO(Py)(Bpy)ClF]PF₆. The shift of the excitation wavelength to the green (488 nm) sharply decreased the MS1 population. The IR-spectral signatures of MS1 were registered. Reverse-transformation Ru-ON (MS1)-Ru-NO (GS) was investigated for [RuNO(Py)(Bpy)ClOH]PF₆ using IR and DSC techniques that made it possible to determine the kinetic parameters (E_a and k₀) and decay temperature. Full article

Two ruthenium nitrosyl complexes of Na[RuNOCl₄L] with nitronyl nitroxide radicals coordinated to ruthenium with N-donor pyridine rings were prepared and described. The crystal structure of both complexes is 1D or 2D polymeric, due to the additional coordination of sodium cation by bridging the chloride ligands or oxygen atoms of nitroxides. Partially, the oligomeric forms remain in the solutions of the complexes in acetonitrile. The magnetic measurements in the solid state demonstrate the presence of antiferromagnetic interactions through the exchange channels, with the distance between paramagnetic centers equal to 3.1–3.9 Å. The electrochemical behavior of the prepared complexes was investigated in acetonitrile solutions. Full article

Herein, we report on the synthesis and characterization of ruthenium compounds with the general formula [RuCl(AA-H)(NO)(dppb]PF₆, where AA = glycine (1), L-alanine (2), L-phenylalanine (3) and L-valine (4), and dppb = 1,4-bis(diphenylphosphine)butane. The complexes were characterized using elemental analysis, UV/Vis and infrared spectroscopies, ¹H, ¹³C, ³¹P NMR techniques, and cyclic voltammetry. Furthermore, the structures of the compounds (1) and (3) were determined using single-crystal X-ray diffraction. In vitro evaluation of the Ru(II)/nitrosyl/amino acid complexes revealed their cytotoxic activities against triple-negative MDA-MB-231 breast cancer cells, and against the non-tumor murine fibroblast cells. All the compounds decreased the percentage of viable cells, inducing cell death by apoptosis. Additionally, the Ru(II) complexes inhibited the migration of MDA-MB-231 cells at concentrations lower than 35 µM, after 48 h of exposure. Thus, these complexes may be promising agents for the treatment of triple-negative MDA-MB-231 breast cancer. Full article

This work aimed to evaluate in vitro DNA binding mechanistically of cationic nitrosyl ruthenium complex [RuNOTSP]⁺ and its ligand (TSPH₂) in detail, correlate the findings with cleavage activity, and draw conclusions about the impact of the metal center. Theoretical studies were performed for [RuNOTSP]⁺, TSPH₂, and its anion TSP⁻² using DFT/B3LYP theory to calculate optimized energy, binding energy, and chemical reactivity. Since nearly all medications function by attaching to a particular protein or DNA, the in vitro calf thymus DNA (ctDNA) binding studies of [RuNOTSP]⁺ and TSPH₂ with ctDNA were examined mechanistically using a variety of biophysical techniques. Fluorescence experiments showed that both compounds effectively bind to ctDNA through intercalative/electrostatic interactions via the DNA helix’s phosphate backbone. The intrinsic binding constants (K_b), (2.4 ± 0.2) × 10⁵ M⁻¹ ([RuNOTSP]⁺) and (1.9 ± 0.3) × 10⁵ M⁻¹ (TSPH₂), as well as the enhancement dynamic constants (K_D), (3.3 ± 0.3) × 10⁴ M⁻¹ ([RuNOTSP]⁺) and (2.6 ± 0.2) × 10⁴ M⁻¹ (TSPH₂), reveal that [RuNOTSP]⁺ has a greater binding propensity for DNA compared to TSPH₂. Stopped-flow investigations showed that both [RuNOTSP]⁺ and TSPH₂ bind through two reversible steps: a fast second-order binding, followed by a slow first-order isomerization reaction via a static quenching mechanism. For the first and second steps of [RuNOTSP]⁺ and TSPH₂, the detailed binding parameters were established. The total binding constants for [RuNOTSP]⁺ (K_a = 43.7 M⁻¹, K_d = 2.3 × 10⁻² M⁻¹, ΔG⁰ = −36.6 kJ mol⁻¹) and TSPH₂ (K_a = 15.1 M⁻¹, K_d = 66 × 10⁻² M, ΔG⁰ = −19 kJ mol⁻¹) revealed that the relative reactivity is approximately ([RuNOTSP]⁺)/(TSPH₂) = 3/1. The significantly negative ΔG⁰ values are consistent with a spontaneous binding reaction to both [RuNOTSP]⁺ and TSPH₂, with the former being very favorable. The findings showed that the Ru(II) center had an effect on the reaction rate but not on the mechanism and that the cationic [RuNOTSP]⁺ was a more highly effective DNA binder than the ligand TSPH₂ via strong electrostatic interaction with the phosphate end of DNA. Because of its higher DNA binding affinity, cationic [RuNOTSP]⁺ demonstrated higher cleavage efficiency towards the minor groove of pBR322 DNA via the hydrolytic pathway than TSPH₂, revealing the synergy effect of TSPH₂ in the form of the complex. Furthermore, the mode of interaction of both compounds with ctDNA has also been supported by molecular docking. Full article

Ruthenium nitrosyl complexes are fascinating photoactive compounds showing complex photoreactivity, such as N→O linkage photoisomerism and NO photorelease. This dual photochemical behavior has been the subject of many experimental studies in order to optimize these systems for applications as photoswitches or therapeutic agents for NO delivery. However, despite recent experimental and computational studies along this line, the underlying photochemical mechanisms still need to be elucidated for a more efficient design of these systems. Here, we present a theoretical contribution based on the calculations of excited-state potential energy profiles for NO dissociation in the prototype trans-[RuCl(NO)(py)₄]²⁺ complex at the complete active space second-order perturbation theory (CASPT2). The results point to a sequential two-step photon absorption photorelease mechanism coupled to partial photoisomerization to a side-on intermediate, in agreement with previous density functional theory calculations. Full article

The photorelease of nitric oxide (NO·) has been investigated in dimethylsulfoxide (DMSO) on two compounds of formula [Ru(R-tpy)(bpy)(NO)](PF₆)₃, in which bpy stands for 2,2′-bipyridine and R-tpy for the 4′-R-2,2′:6′,2″-terpyridine with R = H and MeOPh. It is observed that both complexes are extremely sensitive to traces of water, leading to an equilibrium between [Ru(NO)] and [Ru(NO₂)]. The photoproducts of formula [Ru(R-tpy)(bpy)(DMSO)](PF₆)₂ are further subjected to a photoreaction leading to a reversible linkage isomerization between the stable Ru-DMSO_(S) (sulfur linked) and the metastable Ru-DMSO_(O) (oxygen linked) species. A set of 4 [Ru(R-tpy)(bpy)(DMSO)]²⁺ complexes (R = H, MeOPh, BrPh, NO₂Ph) is investigated to characterize the ratio and mechanism of the isomerization which is tentatively related to the difference in absorbance between the Ru-DMSO_(S) and Ru-DMSO_(O) forms. In addition, the X-ray crystal structures of [Ru(tpy)(bpy)(NO)](PF₆)₃ and [Ru(MeOPh-tpy)(bpy)(DMSO_(S))](PF₆)₂ are presented. Full article

Ruthenium nitrosyl complexes are fascinating versatile photoactive molecules that can either undergo NO linkage photoisomerization or NO photorelease. The photochromic response of three ruthenium mononitrosyl complexes, trans-[RuCl(NO)(py)₄]²⁺, trans-[RuBr(NO)(py)₄]²⁺, and trans-(Cl,Cl)[RuCl₂(NO)(tpy)]⁺, has been investigated using density functional theory and time-dependent density functional theory. The N to O photoisomerization pathways and absorption properties of the various stable and metastable species have been computed, providing a simple rationalization of the photoconversion trend in this series of complexes. The dramatic decrease of the N to O photoisomerization efficiency going from the first to the last complex is mainly attributed to an increase of the photoproduct absorption at the irradiation wavelength, rather than a change in the photoisomerization pathways. Full article

Ruthenium (Ru) complexes have been studied as promising anticancer agents. Ru nitrosyl complex (Ru-NO) is one which acts as a pro-drug for the release of nitric oxide (NO). The Ru-aqueous complex formed by the exchange of NO for a water molecule after NO release could also possess therapeutic effects. This study evaluates the influence of iontophoresis on enhancing the skin penetration of Ru-NO and Ru-aqueous and assesses its applicability as a tool in treating diverse skin diseases. Passive and iontophoretic (0.5 mA·cm⁻²) skin permeation of the complexes were performed for 4 h. The amount of Ru and NO in the stratum corneum (SC), viable epidermis (VE), and receptor solution was quantified while the influence of iontophoresis and irradiation on NO release from Ru-NO complex was also evaluated. Iontophoresis increased the amount of Ru-NO and Ru-aqueous recovered from the receptor solution by 15 and 400 times, respectively, as compared to passive permeation. Iontophoresis produced a higher accumulation of Ru-aqueous in the skin layers as compared to Ru-NO. At least 50% of Ru-NO penetrated the SC was stable after 4 h. The presence of Ru-NO in this skin layer suggests that further controlled release of NO can be achieved by photo-stimulation after iontophoresis. Full article