Structure,electrochemistry and spectroscopy of a new diacylhydrazido-bridged diruthenium complex with a strongly near-infrared absorbing RuIIIRuII intermediate

Reaction of Ru(bpy)₂Cl₂·2 H₂O with 1,2-bis(trifluoroacetyl)hydrazine H₂(adc-CF₃) under basic conditions yields the dinuclear [(μ-adc-CF₃){Ru(bpy)₂}₂]²⁺ ion which was isolated and crystallized for structure determination in the meso diastereoisomer form as the bis(hexafluorophosphate). The Ru ··Ru distance was determined at 5.029(1) Å, and the N–N bond length at 1.463(5) Å reveals a hydrazido(2?) form of the bridge, implying unchanged + II metal oxidation states. Besides bpy-based reduction, the cyclic voltammetric analysis revealed two oxidation waves with a (3+) intermediate. Spectroelectrochemistry demonstrated that this intermediate [(μ-adc-CF₃){Ru(bpy)₂}₂]³⁺ with a comproportionation constant of K_c = 10^8.8 and an absorption at 1680 nm (ε = 9900 M^-1 cm^?1) is a mixed-valent species as evident most convincingly from the EPR parameters at g₁ = 2.239, g₂ = 2.065, g₃ = 1.891 (g_av = 2.101, Δg = g₁ ? g₃ = 0.348).     

Temperature dependence of dual emission in ruthenium(II) complexes containing 3,3′-bi-1,2,4-triazine derivatives

Three new ruthenium(II) polypyridyl complexes with highly π-deficient ligands, [Ru(bpy)₂(btm)]²⁺ (1), [Ru(bpy)₂(btb)]²⁺ (2) and [Ru(bpy)₂(btp)]²⁺ (3) (bpy = 2,2′-bipyridine, btm = 3,3′-bis(5,6-dimethyl-1,2,4-triazine, btb = 3,3′-bis(5,6-diphenyl-1,2,4-triazine, btp = 3,3′-bis(phenanthro[9,10-e][1,2,4]triazine) were synthesized and characterized. Electrochemical data together with molecular calculations show that the first redox process in these complexes is not bpy based. Complexes 1, 2 and 3 display luminescence in ethanol/methanol (4/1, V/V) at 80 K, and all three complexes exhibit a temperature switch from single (150 K) to dual (80 K) emission behavior.     

Preparation and chemical properties of π-conjugated poly(1,10-phenanthroline-3,8-diyl)s with crown ether subunits

π-Conjugated polymers consisting of 1,10-phenanthroline units and crown ether subunits (Poly-1, Poly-2, and Poly-3) were prepared by dehalogenation polycondensation of the corresponding dibromo monomers using a zero-valent nickel complex as a condensing agent. They were characterized by elemental analysis, ¹H NMR and UV–Vis spectroscopies, and cyclic voltammetry (CV). They were partly soluble in CHCl₃, and the number average molecular weight of the soluble part of Poly-2, which had 15-crown-5 subunits, was estimated to be 5300. The polymers exhibited UV–Vis peaks at approximately λ_max = 360 nm, which was reasonable. Complexation with [Ru(bpy)₂]²⁺ and alkaline metal ions made the polymer soluble in organic solvents. The complexation of [Ru(bpy)₂]²⁺ to the 1,10-phenanthroline unit proceeded quantitatively, and the [Ru(bpy)₂]²⁺ complexes exhibited CV curves characteristic of [Ru(N-N)₃]²⁺ complexes.     

Synthesis of enantiomers of mononuclear Ru(II) complexes with 10,13-diaryl substituted dppz ligands

An array of enantiomerically pure mononuclcear [Ru(bpy)₂(dppz)]^2 + derivatives with 10,13-diaryl substituted dppz ligand has been synthesized and characterized (bpy = bipyridine, dppz = pyrido-[3,2-a:2′,3′-c]phenazine). These new complexes exhibit substantially similar absorption spectra, resembling the parent complex [Ru(bpy)₂(dppz)]^2 +, and the enantiomerically pure analogues show the similar CD spectra in buffer solution despite the structural difference.     

Trinuclear Ru(II) polypyridyl complexes as human telomeric quadruplex DNA stabilizers

Two new trinuclear ruthenium(II) complexes [(bpy)₆Ru₃(tpbip)]⁶⁺ (1) and [(bpy)₆Ru₃(tptaip)]⁶⁺ (2) (bpy = 2,2′-bipyridine, tpbip = 1,3,5-tris(1,10-phenanthroline-[5,6-d]imidazol-2-yl)-benzene, tptaip = 2,4,6-tri(1,10-phenanthroline-[5,6-d]imidazol-2-yl)-1,3,5-triazine) have been synthesized and characterized. The interaction of human telomeric DNA with Ru(II) complexes was explored by means of CD spectroscopy, fluorescence titration, ITC and FRET melting. Results indicated that two complexes not only induce a remarkable conformational change of human telomeric DNA, but also have the ability to stabilize the G-quadruplex.     

Aggregation-induced emission of ruthenium(II) polypyridyl complex [Ru(bpy)2(pzta)]2+

A new ruthenium(II) complex [Ru(bpy)₂(pzta)]²⁺ (1) [bpy = 2,2′-bipyridine; pzta = 6-(pyrzin2-yl)-1,3,5-triazine-2,4-diamine] has been synthesized and characterized. This complex exhibits a typical aggregation-induced emission (AIE) behavior that it is faint in solution but intense in the aggregate state.     

Synthesis and characterization of trans-[Ru(NO)Cl(L)4](PF6)2 (L = isonicotinamide; 4-acetylpyridine) and related species

The trans-[RuCl₂(L)₄], trans-[Ru(NO)Cl (L)₄](PF₆)₂ (L = isonicotinamide and 4-acetylpyridine) and trans-[Ru(NO)(OH)(py)₄]Cl₂ (py = pyridine) complexes have been prepared and characterized by elemental analysis, UV–visible, infrared, and ¹H NMR spectroscopies, and cyclic voltammetry. The MLCT band energies of trans-[RuCl₂(L)₄] increase in the order 4-acpy < isn < py. The reduction potentials of trans-[RuCl₂(L)₄] and trans-[Ru(NO)Cl(L)₄]²⁺ increase in the order py < isn < 4-acpy. The stretching band frequency, ν_NO, of the nitrosyl complexes ranges from 1913 to 1852 cm^?1 indicating a nitrosonium character for the NO ligand. Due to the large π-acceptor ability of the equatorial ligands, the coordinated water is much more acidic in the water soluble trans-[Ru(NO)(H₂O)(py)₄]³⁺ than in trans-[Ru(NO)(H₂O)(NH₃)₄]³⁺.     

Characterization of electrochemiluminescence of tris(2,2′-bipyridine)ruthenium(II) with glyphosate as coreactant in aqueous solution

Glyphosate, a phosphorus-containing amino acid type herbicide was used as a coreactant for studying of electrochemiluminescence (ECL) reaction of tris(2,2′-bipyridyl)ruthenium(II) [Ru(bpy)₃²⁺] in an aqueous solution. In a phosphate buffer solution of pH 8, glyphosate itself was known to be electrochemically inactive at glassy carbon electrode, however, it participated in a homogeneous chemical reaction with the electrogenerated Ru(bpy)₃³⁺, and resulted in producing Ru(bpy)₃²⁺ species at the electrode surface. Kinetic and mechanistic information for the catalysis of glyphosate oxidation were evaluated by the steady-state voltammetric measurement with an ultramicroelectrode. The simulated cyclic voltammogram based on this mechanism was in good agreement with that obtained experimentally. ECL reaction of Ru(bpy)₃²⁺/glyphosate system was found to be strongly dependent on the media pH. In a pH region of 5-9, an ECL wave appeared at ca. +1.1 V vs. Ag/AgCl, which was caused by the generation of *Ru(bpy)₃²⁺ via a Ru(bpy)₃³⁺-mediated oxidation of glyphosate. When pH >10, a second ECL wave was observed at ca. +1.35 V vs. Ag/AgCl, which was believed to be associated with a reaction between Ru(bpy)₃³⁺ and the species from direct oxidation of GLYP at a GC electrode surface.     

Design,synthesis, structure and magnetic behavior of a high spin binuclear Fe(III) complex of N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl) amine

The Mannich reaction of 2-aminoethanol, 2-tert-butyl-4-methylphenol, and formaldehyde at the ratio sets of 1:2:2 provided a new ligand, N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L). In the presence of base, H₃L reacted with FeCl₃·6H₂O to form a dinuclear Fe(III) complex [Fe₂L₂] 1. The value of μ_eff at room temperature (5.95 μ_B), is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ ZS(S + 1)]^1/2], indicating there were strong interactions between Fe³⁺ ions. The effective magnetic moment (μ_eff) decreased abruptly with cooling to a minimum value of 0.1 μ_B at 2 K. It was worth noting that Fe³⁺ ions of 1 exhibited thermally induced quartet ? doublet spin transitions, and these transitions were abrupt. The magnetic behaviors of 1 denoted the occurrence of intramolecular anti-ferromagnetic interactions. J (? 13.58 cm^? 1) agrees with the result from Gorun–Lippard equation, ? J (cm^? 1) = Aexp(BP(Å) = 12.9).     

Synthesis and cytotoxicity of a ruthenium nitrosyl nitric oxide donor with isonicotinic acid and a cell penetrating peptide

The syntheses and properties of trans-[Ru(NH₃)₄(L)(NO)](BF₄)₃ (L = isonicotinic acid (inaH) (I) or ina-Tat48–60 (II)) are described. Tat48–60, a cell penetrating peptide fragment of the Tat regulatory protein of the HIV virus, was linked to the ruthenium nitrosyl through inaH. I and II release NO after reduction forming trans-[Ru(NH₃)₄(L)(H₂O)]^3 +. The IC₅₀ values against B16-F10 melanoma cells of I and II (21 μmol L^− 1 and 23 μmol L^− 1, respectively) are close to that of the commercially available cisplatin (33 μmol L^− 1) and smaller than similar complexes. The cytotoxicity is assigned to the NO released from I and II.     

A donor–chromophore complex containing the polyazine bridging ligand 2,3-bis(2-pyridyl)pyrazine

The complex [(PTZpbpy)₂Ru(dpp)](PF₆)₂ coupling a phenothiazine derived electron donor to a ruthenium complex with a polyazine bridging ligand dpp (PTZpbpy = 4-methyl-4′-(4-(N-phenothiazinato)pentyl)-2,2′-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine) has been synthesized and the redox, spectroscopic, and excited state properties elucidated. In the coupled electron donor system, the emission intensity from the Ru(dπ) → dpp(π¹) ³MLCT state is quenched by 94% of that of the analogous system [(bpy)₂Ru(dpp)](PF₆)₂ (bpy = 2,2′-bipyridine) which lacks a coupled electron donor. Coupling a donor–chromophore unit to a bridging ligand will allow the expansion of the molecular architecture to form complex molecular assemblies which contain covalently attached electron donors.     

Ligand concentration and reaction time controlled successive substitution of chloro and η6-benzene of di-μ-chlorobis{η6-benzene)dichlororuthenium(II)} with selenated Schiff base: Formation of half sandwich Ru(II) complex highly active catalyst for oxidation of alcohols

Schiff base (L) synthesized by reacting 2-methylthiobenzeldehyde with 2-(phenylseleno)ethylamine on reaction with di-μ-chlorobis{η⁶-benzene)dichloro-ruthenium(II)}(a) forms two type of species: (i) [Ru(L)₂][PF₆]₂ (1) [L:a = 4:1 and reaction time ～8 h] and (ii) [Ru(η⁶-C₆H₆)(L)][PF₆]₂ (2) [L:a = 2:1 and reaction time ～1 h]. This is first example in which chloro as well benzene ring both are successively substituted by controlling metal:ligand ratio and duration of reaction. The geometry around Ru in complex 1 is distorted octahedral. The 2 has a pseudo-octahedral half sandwich “piano-stool” disposition of ligands around Ru. The Ru–Se distances are 2.4683(10)–2.5082(7) ?. The proton and carbon-13 NMR spectra of L and its both complexes 1 and 2 authenticate them. The 2 shows high catalytic activity for oxidation of primary and secondary alcohols both (TON upto 9.6 × 10⁴; TOF upto 4.80 × 10⁴ h^?1).     

Preparation and characterization of thin films of amine functionalised mesoporous silica having cubic pore structures and their use for electrode surface modifications

Thin films of amine functionalised mesoporous silica were deposited on tin-doped indium oxide (ITO) slides by dip-coating mixtures of TEOS (tetraethyl orthosilicate), APTES ((3-aminopropyl)triethoxysilane), and the non-ionic surfactant Brij56. The pore structure of the films was found to depend on the temperature use during calcination to remove the templates. Films calcined at 350 °C had highly ordered mesostructures with face-centred cubic pore arrangements, while films calcined at 275 °C had primitive cubic pore structures. The as-prepared films, or films extracted with acidic ethanol solutions had very poorly ordered mesopores. Calcination at 275 °C was sufficient to remove the Brij56 templates, without damaging the organic amine chains. Calcination at 350 °C however, also resulted in the lost of the organic groups. The use of ITO substrates allowed the dip-coated films to be used directly as working electrodes. At pH 4.7, the voltammetric response of [Ru(bpy)₃]²⁺ was completely suppressed by the amine functionalised films. This was attributed to protonation of the amine groups that gave the films positive charges. At higher pH, the amine groups were no longer protonated and the voltammetric response of [Ru(bpy)₃]²⁺ was restored. Conversely, [Ru(bpy)₃]²⁺ was adsorbed by the unmodified films that carried negative charges at pH 4.7, resulting in a 4-fold increase in the peak currents compared to uncoated ITO. For [Fe(CN)₆]^3? at low pH the unmodified films blocked the response of the ions, while the functionalised films gave small but distinct voltammetric peaks.     

Polypyridyl ruthenium complexes containing anchoring nitrile groups as TiO2 sensitizers for application in solar cells

Ruthenium polypyridyl complexes of general formula [Ru(bpy)_3 − x(Mebpy-CN)_x]^2 + (x = 1,2 and 3, bpy = 2,2′-bipyridine, Mebpy-CN = 4-methyl-2,2′-bipyridine-4′-carbonitrile) can be used as visible dyes in novel solar cells formed with a porous TiO₂ film (1 cm²), Pt counter-electrode and iodine/iodide as the redox mediator electrolyte dissolved in a polymeric matrix. These complexes can be anchored over the surface of nanocrystalline TiO₂ through nitrile groups, as evidenced by Raman spectra of the adsorbed species. Irradiated by a solar simulator (67 mW cm^− 2), the cells assembled with the Ru complexes with x = 2 and 3 as TiO₂ sensitizers exhibit almost identical current–potential curves, with short-circuit photocurrents of 1.25 mA cm^− 2, fill factors of 0.5 and overall efficiencies around 0.44%. The Ru complex with x = 1 and a similar Re complex did not perform as well as sensitizers. These data were consistent with results obtained from quantum efficiency curves and impedance spectra. We conclude that complexes with nitrile groups as anchoring entities are promising candidates for designing efficient DSCCs.     

A structurally diverse mixed-metal complex with mixed bridging ligands [{[(bpy)2Os(dpp)]2Ru}2(dpq)](PF6)12: Modulating orbital energetics within a supramolecular architecture

A structurally diverse supramolecular complex, [{[(bpy)₂Os(dpp)]₂Ru}₂(dpq)](PF₆)₁₂, has been prepared (bpy = 2,2′-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine, and dpq = 2,3-bis(2-pyridyl)quinoxaline). The supramolecular assembly contains four light absorbing osmium metal centers coupled to two ruthenium metal centers linked by two different bridging ligands (BL) capped by bpy terminal ligands. This supramolecule possesses a lowest unoccupied molecular orbital (LUMO) localized on the central μ-dpq bridging ligand (BL) and a highest occupied molecular orbital (HOMO) localized on the terminal Os centers, providing significant spatial separation of these donor and acceptor orbitals. This hexametallic complex absorbs throughout the visible region due to overlapping singlet metal-to-ligand charge transfer (MLCT) transitions from the Os and Ru chromophores to each π-acceptor ligand. The Os based ³MLCT bands extend into the near-infrared. The light absorbing and redox properties for this hexametallic complex have been elucidated using smaller model fragments and spectroelectrochemistry.     

Electrogenerated chemiluminescence of ruthenium (II) bipyridyl complex directly immobilized on glassy carbon electrodes

Ru(bpy)₃Cl₂ was used to modify the glass carbon electrodes (GCE) by oxidation and co-deposition on the electrode surface. The modified electrodes were characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). About 2.2 × 10⁻⁹ mol Ru(bpy)₃ ²⁺ was immobilized on the GCE surface (ϕ = 4 mm). The modified GC electrodes showed stable electrochemiluminescence with tripropylamine (TPrA) as the co-reactant with a linear range from 10 to 500 μM (R ² = 0.999). Among the 10 amino acids tested, the modified electrode system showed selective response to arginine and lysine, indicating that the molecular structure played an important role as co-reactant. This simple and sensitive electrode modifying method when combined with flow-injection or liquid chromatography systems has the potential for amino acid analyses.     

Efficient green-colored electrochemiluminescence from cyclometalated iridium(III) complex

The spectroscopy, electrochemistry, and electrochemiluminescence (ECL) of cyclometalated iridium(III) bis(2-(p-tolyl)pyridinato-N, C^2′) (picolinate) [(tpy)₂Ir(pico)] was investigated. (tpy)₂Ir(pico) shows high photoluminescence efficiency (Φ_PL = ∼0.31) and quasi-reversible redox behaviors in acetonitrile solution. Intense green ECL was observed from all three modes of ECL generation (annihilation, oxidative-reduction, and reductive-oxidation). Relative ECL efficiencies with or without coreactants from (tpy)₂Ir(pico) were estimated using Ru(bpy)₃²⁺ (bpy, 2,2′-bipyridine) as a relative standard. Typically, in the reductive-oxidation process with peroxodisulfate (S₂O₈²⁻), (tpy)₂Ir(pico) produces 8-fold more efficient ECL at approximately 531 nm than Ru(bpy)₃². This efficient green ECL indicates potential for the development of multicolored ECL analysis in addition to standard Ru(bpy)₃²⁺ systems.     

Highly efficient Ru/Sm2O3-CeO2 catalyst for ammonia synthesis

A series of Ru/Sm₂O₃–CeO₂ catalysts were prepared by using a co-precipitation (CP) method and characterized by XRD, BET, SEM, H₂-TPD-MS, H₂-TPR and CO chemisorption. The activity test shows that ammonia concentration of the catalyst with 7% Sm is 13.4% at 10 MPa, 10,000 h^− 1, 425 °C, which is 21% higher than that of Ru/CeO₂. Such high catalytic activity was due to three effects: the morphology changes of catalyst, electrodonating property of partially reduced CeO_2 − x to Ru metal and the property of easily hydrogen desorption derived from the presence of Sm³⁺ in ceria.     

Cytotoxic organometallic [Ru(η6-anethole)(en)(X)]PF6 (X = Br or I) complexes: Synthesis,characterization and in vitro biological evaluation

Two new organometallic compounds with the general formula [Ru(η⁶-anethole)(en)(X)]PF₆, where X = Br (5) or I (6) and en = ethylenediamine, were synthesized and fully characterized using standard techniques (NMR, MS and elemental analysis). Displacement of the proton and carbon aromatic chemical shifts of anethole to the upper field in both compounds indicated organometallic Ru(η⁶-anethole) bond formation, and the characteristic “piano-stool” structure of these types of compounds was confirmed by the single crystal X-ray diffraction of compound 5. Compounds 5 and 6 exhibited interesting cytotoxicity, especially toward the human colon tumor cell line HT-29, similar to the previously studied compound [Ru(η⁶-anethole)(en)(Cl)]PF₆ (4). A slight tendency toward cytotoxicity could be observed by varying the halogen leaving group (IC₅₀ value): 6 (10 ± 2 μM) > 5 (18 ± 2 μM) = 4 (18 ± 3 μM). Compound 6 showed 3-fold more biological activity in HT-29 cells than toward the non-tumor colon cell line CCD-841, making it an interesting candidate for further studies and drug development.     

Investigation of inducing apoptosis in human lung cancer A549 cells and related mechanism of a ruthenium(II) polypyridyl complex

Two Ru(II) polypyridyl complexes [Ru(bpy)₂(pztp)]^2 + (Ru1) and [Ru(bpy)₂(pytp)]^2 + (Ru2) were synthesized and characterized. Our data demonstrated that Ru2 displayed relatively higher cytotoxic activity against lung cancer A549 cells and had higher selectivity between tumor and normal cells in comparison with cisplatin. Studies on the molecular mechanism revealed that Ru2 caused cell cycle arrest at G2/M in A549 cells and induced apoptosis through a ROS-mediated mitochondrial dysfunction pathway. The further studies by comet assay at single cell level indicated that DNA damage in A549 cells was triggered by Ru2, following with the up-regulation of phosphorylated ATM (Ser1984), Histone H2A.X (Ser139) and p53 (Ser15). Western blot analysis suggested that MAPKs signaling pathways, especially ERK, were involved in Ru2-induced apoptosis. Moreover, both DNA damage and MAPKs signaling pathways were regulated by the level of ROS. To our knowledge, this is the first report of the ruthenium (II) polypyridyl complex which induces apoptosis partly through the activation of ERK.