Search Results (233)

A novel ruthenium(II) complex, [RuCl₂(η⁶-p-cymene)(bph-κN)] (1), was synthesized and structurally characterized using FTIR and NMR spectroscopy. Density functional theory (DFT) calculations supported the proposed geometry and allowed for comparative analysis of experimental and theoretical spectroscopic data. The interaction of complex 1 with human serum albumin (HSA) and calf thymus DNA was investigated through fluorescence quenching experiments, revealing spontaneous binding driven primarily by hydrophobic interactions. The thermodynamic parameters indicated mixed quenching mechanisms in both protein and DNA systems. Ethidium bromide displacement assays and molecular docking simulations confirmed DNA intercalation as the dominant binding mode, with a Gibbs free binding energy of −34.1 kJ mol⁻¹. Antioxidant activity, assessed by EPR spectroscopy, demonstrated effective scavenging of hydroxyl and ascorbyl radicals. In vitro cytotoxicity assays against A375, MDA-MB-231, MIA PaCa-2, and SW480 cancer cell lines revealed selective activity, with pancreatic and colorectal cells showing the highest sensitivity. QTAIM analysis provided insight into metal–ligand bonding characteristics and intramolecular stabilization. These findings highlight the potential of 1 as a promising candidate for further development as an anticancer agent, particularly against multidrug-resistant tumors. Full article

Searching for new and efficient transfer hydrogenation catalysts, a series of new organometallic ruthenium(II)-arene complexes of the formulae [Ru(η⁶-p-cymene)(L)Cl][PF₆] (1–8) and [Ru(η⁶-p-cymene)(L)Cl][Ru(η⁶-p-cymene)Cl₃] (9–11) were synthesized and fully characterized. These were prepared from the reaction of pyridine–quinoline and biquinoline-based ligands (L) with [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂, in 1:2 and 1:1, metal (M) to ligand (L) molar ratios. Characterization includes a combination of spectroscopic methods (FT-IR, UV-Vis, multi nuclear NMR), elemental analysis and single-crystal X-ray crystallography. The pyridine–quinoline organic entities encountered, were prepared in high yield either via the thermal decarboxylation of the carboxylic acid congeners, namely 2,2′-pyridyl-quinoline-4-carboxylic acid (pqca), 8-methyl-2,2′-pyridyl-quinoline-4-carboxylic acid (8-Mepqca), 6′-methyl-2,2′-pyridyl-quinoline-4-carboxylic acid (6′-Mepqca) and 8,6′-dimethyl-2,2′-pyridyl-quinoline-4-carboxylic acid (8,6′-Me₂pqca), affording the desired ligands pq, 8-Mepq, 6′-Mepq and 8,6′-Me₂pq, or by the classical Friedländer condensation, to yield 4,6′-dimethyl-2,2′-pyridyl-quinoline (4,6′-Me₂pq) and 4-methyl-2,2′-pyridyl-quinoline (4-Mepq), respectively. The solid-state structures of complexes 1–4, 6, 8 and 9 were determined showing a distorted octahedral coordination geometry. The unit cell of 3 contains two independent molecules (Ru-3), (Ru′-3) in a 1:1 ratio, due to a slight rotation of the arene ring. All complexes catalyze the transfer hydrogenation of acetophenone, using 2-propanol as a hydrogen donor in the presence of KOiPr. Among them, complexes 1 and 5 bearing methyl groups at the 8 and 4 position of the quinoline moiety, convert acetophenone to 1-phenylethanol quantitatively, within approximately 10 min with final TOFs of 1600 h⁻¹. The catalytic performance of complexes 1–11, towards the transfer hydrogenation of p-substituted acetophenone derivatives and benzophenone, ranges from moderate to excellent. An inner-sphere mechanism has been suggested based on the detection of ruthenium(II) hydride species. Full article

Four new arene–ruthenium(II) complexes [(η⁶-p-cymene)RuCl(dpm)], where dpm are hexa-(L3–L5) and meso-substituted (L6) dipyrromethene ligands, were synthesized. These ligands and the corresponding complexes were thoroughly characterized by elemental analysis and spectroscopic techniques (MS, IR, ¹H, ¹³C NMR, and UV–vis), and the structures of one ligand and three ruthenium complexes were determined by X-ray single-crystal analysis. The DNA-binding ability of the Ru-3–Ru-6 complexes was evaluated by UV–vis DNA titration. Compound Ru-3 exhibited the highest binding energy, outperforming the complexes containing a dipyrrin ligand substituted by chlorides (Ru-4 and Ru-5) or a meso-substituted dipyrrin (Ru-6). Molecular docking revealed that the hypothetical Ru-1 and Ru-2 complexes, which contain iodide ligands in the dipyrrin structures, showed higher DNA-binding affinities than Ru-3. Computational calculations supported the experimental results, confirming that Ru-3 has a higher affinity for DNA than the other complexes. Full article

Over the last nine decades, 2,2′:6′,2″-terpyridine (terpy) derivatives and their transition d-metal complexes have been extensively explored due to their unique and widely tuned optical, electrochemical, and biological properties. Terpyridyl transition metal complexes occupy a prominent position among functional molecular materials for applications in optoelectronics, life science, catalysis, and photocatalysis, as well as they have played a key role in determining structure–property relationships. This review summarizes the developments of amine-functionalized R-C₆H₄-terpy systems and their d-metal complexes, largely concentrating on their photophysical and electrochemical properties. Functionalization of the terpy core with the electron-rich group, attached to the central pyridine ring of the terpy backbone via the phenylene linker, gives rise to organic push–pull systems showing the photoinduced charge flow process from the peripheral donor substituent to the terpy acceptor. The introduction of amine-functionalized R-C₆H₄-terpy systems into the coordination sphere of a d-metal ion offers an additional way for controlling the photophysics of these systems, in agreement with the formation of the excited state of intraligand charge transfer (ILCT) nature. Within this review, a detailed discussion has been presented for R-C₆H₄-terpys modified with acyclic and cyclic amine groups and their Cr(III), Mn(I), Re(I), Fe(II), Ru(II), Os(II), Pt(II), and Zn(II) coordination compounds. Full article

Glyphosate (GP) and its derivatives are present in almost all environments and suspected to induce acute and chronic kidney injuries. This public health issue is relatively underexplored. We therefore conducted an investigation on rats and tubular HK2 cells cultured for 24 h to determine whether GP’s and Roundup’s^® (RU) potential renal toxicity might be related to mitochondrial respiration impairment and the increased production of hydrogen peroxide (H₂O₂) in both the renal cortex and medulla (involved in filtration and reabsorption, respectively) using a high-resolution oxygraph (Oxygraph-2K, Oroboros instruments). GP alone decreased maximal uncoupled mitochondrial respiration in the medulla (−14.2%, p = 0.02). RU decreased mitochondrial respiratory chain complexes I and I + II and the maximal respiratory capacity both in the renal cortex (−13.5%, p = 0.04; −20.1%, p = 0.009; and −14.7%, p = 0.08, respectively) and in the medulla for OXPHOS I + II (80.82 ± 7.88 vs. 61.03 ± 7.67 pmol/(s·mL), −24.5%, p = 0.003). Similarly, in HK2 cells, the decrease in OXPHOS CI + II was greater after RU (65.87 ± 1.30 vs. 51.82 ± 3.50 pmol/(s·mL), −21.3%, p = 0.04) compared to GP. Increased H₂O₂ production was mainly observed after RU in the medulla (+14.3% in OXPHOS CI + II, p = 0.04) and in HK2 cells (+19% in OXPHOS CI + II, p = 0.02). In conclusion, although the medulla might be more prone to GP-related mitochondrial damage, RU toxicity was greater in both the renal cortex and medulla and in cultured tubular HK2 cells. Enhancing mitochondrial respiration and reducing oxidative stress might favor the prevention of or reduction in such worldwide-used herbicides’ deleterious effects on the kidneys. Full article

A ligand exchange reaction between [Ru₂(npc)₂(O₂CMe)₂] (1; npc = 1,8-naphthyridine-2-carboxylate) and trifluoroacetic acid yielded the diruthenium naphthyridine complex with two trifluoroacetate ligands, [Ru₂(npc)₂(O₂CCF₃)₂] (2), which was structurally characterized by electrospray ionization mass spectrometry, elemental analysis, infrared spectrum, and synchrotron single-crystal X-ray diffraction. The crystal structure of 2 adopts a paddlewheel-type structure in which two npc and two O₂CCF₃ ligands are coordinated in a cis-2:2 arrangement around the Ru₂ core. The temperature-dependent magnetic susceptibility measurements indicated that 2 has (i) an S = 1 spin state for the Ru₂⁴⁺ core and (ii) a large D value of 243 cm⁻¹; characteristic of paddlewheel-type Ru₂ complexes. The cyclic voltammetry measurements indicated that 2 exhibited one reversible oxidation wave (E_1/2 = 0.72 V vs. SCE) and two reduction waves (E_1/2 = −0.67 and −1.10 V vs. SCE); which were clearly positively shifted when compared with those of 1. Additionally, the absorption spectrum of 2 displayed intense absorption bands in the visible region; attributed to metal-to-ligand charge transfer from the Ru₂ core to the npc ligands; which were blue-shifted by approximately 70–100 nm when compared with those of 1. These distinct shifts in redox potentials and absorption bands originated from the strong electron-withdrawing effect of the O₂CCF₃ ligands in 2. Full article

Almost forty years ago, dye-sensitized solar cells (DSSCs) appeared as a promising route for harnessing the energy of the sun and for converting it into electricity. In the following years, a huge number of studies have been dedicated to increase the global photovoltaic efficiencies and stability of DSSCs. Thiocyanate ruthenium complexes bearing chelating nitrogen donor ligands turned out to be among the best performing photosensitizers. In the last 15 years, a lot of work has also been dedicated to the preparation of efficient thiocyanate-free Ru dyes. In this review, these two families of ruthenium(II) complexes are presented: (a) dyes presenting thiocyanate ligands and (b) thiocyanate-free dyes. The coverage, mainly from 2021, is not exhaustive, but exemplifies the most recent design approaches and photovoltaic properties of these two classes of Ru(II) photosensitizers. Full article

Adsorption of mononuclear tris(bipyridine) ruthenium(II) complexes and binuclear tris(bipyridine) ruthenium(II) complexes equipped with carboxyl groups (-COOH) on the (111) surface of TiO₂ crystal in anatase form was modeled using Monte Carlo simulations, applying the Universal force field. It was shown that the adsorption efficiency of the ruthenium-based dyes on the TiO₂ surface depends on the position of the anchoring -COOH group in the molecular structure. The increase in the number of possible anchor groups in the dyes increases their ability to deposit on the surface of semiconductors. The chemisorbed molecules, such as mononuclear tris(bipyridine) ruthenium(II) complexes with the -COOH group in para position (RuLp) and binuclear tris(bipyridine) ruthenium(II) complexes called B3 with two anchoring -COOH groups and phenyl in the spacer, interact with the adsorber and other neighboring dyes, changing their electron and optical properties. The obtained computational results help to explain the behavior of the dyes on the TiO₂ surface, giving impact on their DSSC applications. Full article

Density functional theory (DFT) calculations were employed to study a series of complexes of general formula [Ru(salen)(X)(CO)]^0/−1 (X = Cl⁻, F⁻, SCN⁻, DMSO, Phosphabenzene, Phosphole, TPH, CN⁻, N₃⁻, NO₃⁻, CNH⁻, NHC, P(OH)₃, PF₃, PH₃). The effect of ligands X on the Ru-CO bond was quantified by the trans-philicity, Δσ¹³C NMR parameter. The potential of Δσ¹³C to be used as a probe of the CO photodissociation by Ru(II) transition metal complexes is established upon comparing it with other trans-effect parameters. An excellent linear correlation is found between the energy barrier for the Ru-CO photodissociation and the Δσ¹³C parameter, paving the way for studying photoCORMs with the ¹³C NMR method. The strongest trans-effect on the Ru-CO bond in the [Ru(salen)(X)(CO)]^0/−1 complexes are found when X = CNH⁻, NHC, and P(OH)₃, while the weakest for X = Cl⁻, NO₃⁻ and DMSO trans-axial ligands. The Ru-CO bonding properties were scrutinized using Natural Bond Orbital (NBO), Natural Energy Decomposition Analysis (NEDA) and Natural Orbital of Chemical Valence (NOCV) methods. The nature of the Ru-CO bond is composite, i.e., electrostatic, covalent and charge transfer. Both donation and backdonation between CO ligand and Ru metal centre equally stabilize the Ru(II) complexes. Ru-CO photodissociation proceeds via a ³MC triplet excited state, exhibiting a conical intersection with the T₁ ³MLCT excited state. Calculations show that these complexes show bands within visible while they are expected to be red emitters. Therefore, the [Ru(salen)(X)(CO)]^0/−1 complexes under study could potentially be used for dual action, photoCORMs and theranostics compounds. Full article

Two new Ru(II) complexes, mononuclear [RuCl₂(η⁶-p-cymene)(3,4-dmph-κN)] (1) and the binuclear complex [{RuCl(η⁶-p-cymene)}₂(μ-Cl)(μ-3,4-dmph-κ²N,N′)]Cl (2; 3,4-dmph = 3,4-dimethylphenylhydrazine), are synthesized and experimentally and theoretically structurally characterized utilizing ¹H and ¹³C NMR and FTIR spectroscopy, as well as DFT calculations. Degradation product of 2, thus ([{RuCl(η⁶-p-cymene)}₂(μ-Cl)(μ-3,4-dmph-κ²N,N′)][RuCl₃(η⁶-p-cymene)] (2b) was characterized with SC-XRD. In the crystals of 2b, the cationic and anionic parts interact through N-H^...Cl hydrogen bridges. The spectrofluorimetric measurements proved the spontaneity of the binding processes of both complexes and HSA. Spin probing EPR measurements implied that 1 and 2 decreased the amount of bound 16-doxylstearate and implicated their potential to bind to HSA more strongly than the spin probe. The cytotoxicity assessment of both complexes against the MDA-MB-231 and MIA PaCa-2 cancer cell lines demonstrated a clear dose-dependent decrease in cell viability and no effect on healthy HS-5 cells. Determination of the malondialdehyde and protein carbonyl concentrations indicated that new complexes could offer protective antioxidant benefits in specific cancer contexts. Gel electrophoresis measurements showed the reduction in MMP9 activity and indicated the potential of 1 in limiting the cancer cells’ invasion. The annexin V/PI apoptotic assay results showed that 1 and 2 exhibit different selectivity towards MIA PaCa-2 and MDA-MB-231 cancer cells. A comparative molecular docking analysis of protein binding, specifically targeting acetylcholinesterase (ACHE), matrix metalloproteinase-9 (MMP-9), and human serum albumin (HSA), demonstrated distinct binding interactions for each complex. Full article

Two bis-ruthenium(II) complexes, namely N,N′-{5,17-diamino-4(24),6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]arene}-bis-[dichloro-(p-cymene)-ruthenium(II)] (1) and N,N′-{5,11-diamino-4(24),6(10),12(16), 18(22)-tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]arene}-bis-[dichloro-(p-cymene)-ruthenium(II)] (2) were synthesized and tested as catalysts in the N-alkylation of primary amines with arylmethyl alcohol using the green “hydrogen borrowing” methodology. The catalytic results were compared with those obtained when the N-{5-amino-4(24),6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetrapentyl-resorcin[4]arene}-[dichloro-(p-cymene)-ruthenium(II)] (3) complex was employed as catalyst. The rate of the N-alkylation of aniline with benzyl alcohol increased in the order 3 < 1 ≪ 2, which highlights the importance of the relative positioning of the two metal centers on the upper rim of the resorcin[4]arene. Theoretical investigations suggest that the grafting of the two “RuCl₂(p-cymene)NH₂” moieties on two distal aromatic rings of the cavitand allows a cooperative effect between a ruthenium atom and the coordinated amine of the second metal center. Full article

This work demonstrates the synthesis of a series of Ru(II) complexes with dibenzimidazole-based ligands and investigates the spatial relationship between ligand structure and complexes. It explores the effect of substituent changes on the N-Ru-N bond angle of the complexes, as well as the distance from the Ru center to the aryl group, and utilizes these complexes to catalyze benzyl alcohol dehydrogenation in toluene. It was found that the ligand [Ru]-complex with a spatial configuration of electron donating groups had a larger N-Ru-N bond angle and higher catalytic performance at the ruthenium center, with a yield of 91.2%. Moreover, its distance from the umbrella hydrocarbon was sufficient to allow for the attack of the reactant molecules and the occurrence of catalytic reactions. The reaction mechanism was subsequently derived. This manuscript is expected to provide assistance and inspiration for the development of high-performance catalysts for alcohol dehydrogenation reactions. Full article

The oxime group is important in organic and inorganic chemistry. In most cases, this group is part of an organic molecule possessing one or more donor sites capable of forming bonds to metal ions. One family of such compounds is the group of 2-pyridyl (aldo)ketoximes. Metal complexes of 2-pyridyl oximes continue to attract the intense interest of many inorganic chemistry groups around the world for a variety of reasons, including their interesting structures, physical and biological properties, and applications. A unique member of 2-pyridyl ketoximes is di-2-pyridyl ketoxime (dpkoxH), which contains two 2-pyridyl groups and an oxime functionality that can be easily deprotonated giving the deprotonated ligand (dpkox⁻). The extra 2-pyridyl site confers a remarkable flexibility resulting in metal complexes with exciting structural and reactivity features. Our and other research groups have prepared and characterized many metal complexes of dpkoxH and dpkox⁻ over the past 30 years or so. This work is an attempt to build a “periodic table” of dpkoxH, which is near completion. The filled spaces of this “periodic table” contain metal ions whose dpkoxH/dpkox⁻ complexes have been structurally characterized. This work reviews comprehensively the to-date published coordination chemistry of dpkoxH with emphasis on the syntheses, reactivity, relationship to metallacrown chemistry, structures, and properties of the metal complexes; selected unpublished results from our group are also reported. The sixteen coordination modes adopted by dpkoxH and dpkox⁻ have provided access to monomeric and dimeric complexes, trinuclear, tetranuclear, pentanuclear, hexanuclear, heptanuclear, enneanuclear, and decanuclear clusters, as well as to a small number of 1D coordination polymers. With few exceptions ({M^IILn^III₂} and {Ni^II₂Mn^III₂}; M = Ni, Cu, Pd, and Ln = lanthanoid), most complexes are homometallic. The metals whose ions have yielded complexes with dpkoxH and dpkox⁻ are Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Cd, Re, Os, Ir, Au, Hg, lanthanoids (mainly Pr and Nd), and U. Most metal complexes are homovalent, but some mixed-valence Mn, Fe, and Co compounds have been studied. Metal ion-assisted/promoted transformations of dpkoxH, i.e., reactivity patterns of the coordinated ligand, are also critically discussed. Some perspectives concerning the coordination chemistry of dpkoxH and research work for the future are outlined. Full article

This study explores poly(methyl methacrylate) (PMMA)-based composites as potential alternatives to conventional TiO₂-based photocatalysts. Specifically, it examines PMMA composites enriched with oxo–titanium(IV) complexes, [Ti₈O₂(OⁱPr)₂₀(man)₄] (1), [Ti₄O(OⁱPr)₁₀(O₃C₁₄H₈)₂] (2), and [Ti₆O₄(OⁱPr)₂(O₃C₁₄H₈)₄(O₂CEt)₆] (3), alongside ruthenium(III) complexes, K[Ru(Hedta)Cl]∙2H₂O (4) and [Ru(pic)₃]·H₂O (5). We assessed the physicochemical, adsorption, and photocatalytic properties of these composites with structural analyses (Raman spectroscopy, X-ray absorption (XAS), and SEM-EDX), confirming the stability of complexes within the PMMA matrix. Composites containing titanium(IV) compounds demonstrated notably higher photocatalytic efficiency than those with ruthenium(III) complexes. Based on activity profiles, composites were categorized into three types: (i) UV-light active (complexes (1) and (2)), (ii) visible-light active (complexes (4) and (5)), and (iii) dual-range active (complex (3)). The results highlight the strong potential of titanium(IV)–PMMA composites for UV-driven photocatalysis. Moreover, their activity can be extended to the visible range after structural modifications. Ruthenium(III)–PMMA composites, in turn, showed superior performance under visible light. Overall, PMMA composites with titanium(IV) or ruthenium(III) complexes demonstrate promising photocatalytic properties for applications using both UV and visible light ranges. Full article

Homogeneous aptasensors that eliminate the need for probe labeling or immobilization hold significant potential for the rapid detection of tumor biomarkers. Herein, a homogeneous aptasensor with electrochemical (EC) and electrochemiluminescence (ECL) dual detection channels was developed by integrating nanochannel-based probe enrichment and DNase I cleavage for selective detection of the tumor biomarker, carbohydrate antigen 125 (CA125). A two-dimensional (2D) composite probe was prepared by assembling the CA125-specific aptamer and the cationic probe tris(2,2′-bipyridyl)Ru(II) (Ru(bpy)₃²⁺), which exhibited both EC and ECL properties, onto graphene oxide (GO) nanosheets (Ru(bpy)₃²⁺/Apt@GO). A vertically ordered mesoporous silica film (VMSF) with ultrasmall, uniform, and vertically aligned nanochannel arrays was rapidly grown on the inexpensive and disposable indium tin oxide (ITO) electrode, forming the detection interface. Due to the size exclusion effect of the ultrasmall nanochannels in VMSF, the Ru(bpy)₃²⁺/Apt@GO probe was unable to penetrate the nanochannels, resulting in no detectable Ru(bpy)₃²⁺ signal on the electrode. Upon specific recognition of CA125 by the aptamer, an aptamer-CA125 complex was formed and subsequently detached from GO. DNase I then cleaved the aptamer-CA125 complex, releasing CA125 and allowing Ru(bpy)₃²⁺ to dissociate into the solution. This enzymatic cleavage enabled CA125 to re-enter the binding cycle, amplifying the release of Ru(bpy)₃²⁺ into the solution. The electrostatic adsorption of the cationic Ru(bpy)₃²⁺ by VMSF significantly enhanced both the EC and ECL signals. The constructed aptasensor exhibited a linear EC detection range for CA125 from 0.1 U/mL to 100 ng/mL, with a limit of detection (LOD) of 91 mU/mL. For ECL detection, CA125 was detected over a range from 0.001 to 100 U/mL, with a LOD as low as 0.4 mU/mL. The developed aptasensor demonstrated excellent selectivity and was successfully applied to the dual-mode EC/ECL detection of CA125 in fetal bovine serum samples. Full article