Characterization of the low-oxidation-potential electrogenerated chemiluminescence of tris(2,2′-bipyridine)ruthenium(II) with tri-n-propylamine as coreactant

The electrogenerated chemiluminescence (ECL) of the Ru(bpy)₃²⁺ (bpy, 2,2′-bipyridine)/tri-n-propylamine (TPrA) system can be produced at an oxidation-potential well before the oxidation of Ru(bpy)₃²⁺. Here, we describe the unique features of the low-oxidation-potential (LOP) ECL. The LOP ECL exhibited strong dependence on solution pH with the maximum emission at pH  7.7. Compared with the conventional ECL, the LOP ECL was much more significantly diminished at high pH (>10), probably due to the short lifetime of TPrA cation radical which is a crucial intermediate for the LOP emission. It was also found that the preceding deprotonation step played an important role in TPrA oxidation at neutral pH and would remarkably influence the emission intensity. As excess intermediate radicals were produced upon rapid TPrA oxidation, only 5 mM TPrA was needed to achieve the maximum LOP ECL intensity in detecting trace Ru(bpy)₃²⁺ (<1 μM) and the LOP ECL response to Ru(bpy)₃²⁺ concentration was linear. Compared with the conventional Ru(bpy)₃²⁺/TPrA ECL, the LOP ECL technique not only produces higher emission intensity at lower oxidation-potential, but also significantly reduces the amount of the coreactant.     

Effect of Ionic Strength on the Electrochemiluminescence Generation by Tris(2,2'-bipyridyl)ruthenium(II)/Tri-n-propylamine

Electrochemiluminescence(ECL) is a powerful transduction technique used in biosensing and in vitro diagnosis, while the mechanism of ECL generation is complicated and affected by various factors. Herein the effect of ionic strength on ECL generation by the classical tris(2,2'-bipyridyl)ruthenium(II)[Ru(bpy)₃²⁺]/tri-n-propylamine(TPrA) system was investigated. It is clear that the ECL intensity decreases significantly with the increase of ionic strength, most likely arising from the reduced deprotonation rate of TPrA^+·. We further combined microtube electrode(MTE) with ECL microscopy to unravel the evolution of ECL layer with the variation of ionic strength. At a low concentration of Ru(bpy)₃²⁺, the thickness of ECL layer(TEL) nearly kept unchanged with the ionic strength, indicating the surface-confined ECL generation is dominated by the oxidative-reduction route. While at a high concentration of Ru(bpy)₃²⁺, ECL generation is dominated by the catalytic route and TEL increases remarkably with the increase of ionic strength, because of the extended diffusion length of Ru(bpy)₃³⁺ at a reduced concentration of TPrA^·.     

Hydrogen peroxide photoproduction by the semicarbazide—tris(2,2′-bipyridine)ruthenium(II)—oxygen system

A light-driven system consisting of tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺) as the photosensitizer, semicarbazide as the electron donor and molecular oxygen as the electron acceptor has been employed for hydrogen peroxide production. The efficiency of this photosystem markedly depends on pH: while the peroxide yield is almost negligible at acid, neutral or slightly alkaline pH, it reaches significant values at high hydroxide concentrations, the initial rate of H₂O₂ formation drastically increasing from pH 12 to pH 14. In 1 M NaOH solutions containing Ru(bpy)₃²⁺ and semicarbazide at optimum concentrations, the number of catalytic cycles (or turnover number) undergone by the ruthenium complex over the complete course of the photochemical reaction is as high as 1.1 × 10⁴.

Spectrofluorometric and laser flash photolysis techniques were used to study the primary photochemical reactions involving the excited state of the ruthenium complex as well as the photochemically generated species Ru(bpy)₃³⁺ and Ru(bpy)₃⁺. It is proposed that at pH 14 a sequence of reactions leading to O₂ photoreduction by electrons from semicarbazide takes place, with the concomitant formation of H₂O₂; the excited state of Ru(bpy)₃²⁺ appears to react via oxidative quenching by oxygen rather than via reductive quenching by semicarbazide. At neutral pH, in contrast, there is no H₂O₂ formation owing to the fact that semicarbazide is unable to reduce (Ru(bpy)₃³⁺ to Ru(bpy)₃²⁺, although the photoexcited ruthenium complex is quenched equally by oxygen.     

Electrochemiluminescence sensor using tris(2,2′-bipyridyl)ruthenium(II) immobilized in Eastman-AQ55D–silica composite thin-films

An electrochemiluminescence (ECL) sensor with good long-term stability and fast response time has been developed. The sensor was based on the immobilization of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) into the Eastman-AQ55D–silica composite thin films on a glassy carbon electrode. The ECL and electrochemistry of Ru(bpy)₃²⁺ immobilized in the composite thin films have been investigated, and the modified electrode was used for the ECL detection of oxalate, tripropylamine (TPA) and chlorpromazine (CPZ) in a flow injection analysis system and showed high sensitivity. Because of the strong electrostatic interaction and low hydrophobicity of Eastman-AQ55D, the sensor showed no loss of response over 2 months of dry storage. In use, the electrode showed only a 5% decrease in response over 100 potential cycles. The detection limit was 1 μmol l⁻¹ for oxalate and 0.1 μmol l⁻¹ for both TPA and CPZ (S/N=3), respectively. The linear range extended from 50 μmol l⁻¹ to 5 mmol l⁻¹ for oxalate, from 20 μmol l⁻¹ to 1 mmol l⁻¹ for TPA, and from 1 μmol l⁻¹ to 200 μmol l⁻¹ for CPZ.     

Determination of Amino Acids by Ru(bpy)_3~(2+) Cathodic Electrochemiluminescence with High Sensitivity

The unique cathodic electrochemiluminescence(ECL) emission of Ru(bpy)32+(bpy=2,2′-bipyridine) was observed via Nafion film at Au electrode[Au/Nafion/Ru(bpy)32+] at about 0.20 V(vs. Ag/AgCl) and applied to the determination of several amino acids without prior derivatization with high sensitivity. The cathodic electrochemilumi-nescence(ECL) exhibits the detection limits and linear ranges of several amino acids comparable to or better than those of capillary electrophoresis with conventional ECL detection method(at 1.10—1.20 V vs. Ag/AgCl) based on precolumn derivatization. The results suggest that the cathodic ECL is promising for the detection of amino acids in bioanalysis.     

Preparation,Characterization, Luminescent and Electrochemical Properties of Ru(bpy)2-functionalized Silica Nanoparticles

Ru(II)-complex functionalized silica nanoparticles(nano-SiO₂) were prepared via a coordination reaction of cis-dichlorobis(2,2'-bipyridine)ruthenium[Ru(bpy)₂Cl₂] complex with poly(4-vinylpyridine)(P4VP)-modified nano-SiO₂ particles. Both the Ru-complex and the functionalized nano-SiO₂P4VP-Ru(bpy) hybrids were doped in poly(methyl methacrylate)(PMMA) to form optically transparent thin films. The composition and spectroscopic properties of the nano-SiO₂P4VP-Ru(bpy) hybrids were evaluated with the help of thermogravimetric and elemental analysis, and UV-Vis absorption spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, and fluorescence spectroscopy. Microscopy images revealed that the nanohybrids were approximately 12 nm in diameter and readily formed aggregates following the functionalization with P4VP and Ru(bpy)₂Cl₂. The as-prepared nano-SiO₂P4VP-Ru(bpy) hybrids produced emissions at approximately 604 and 654 nm under radiation both in solution and in doped thin films. Finally, cyclic voltammetry studies on the nanohybrid-modified electrode revealed a redox couple with the cathodic and anodic potentials at approximately 0.28 and 0.73 V(vs. Ag/AgCl), attributed to the one electron transfer of Ru(bpy)₂^2+/3+ immobilized on the nano-SiO₂ particles.     

Photophysics of ruthenium(II) complexes with 2-(2′-pyridyl) pyrimidine and 2,2′-bipyridine ligands in fluid solution

The photophysics of three complexes of the form Ru(bpy)₃₋(pypm)²⁺ (where bpy2,2′-bipyridine, pypm 2-(2′-pyridyl)pyrimidine and P=1, 2 or 3) was examined in H₂O, propylene carbonate, CH₃CN and 4:1 (v/v) C₂H₅OH---CH₃OH; comparison was made with the well-known photophysical behavior of Ru(bpy)₃²⁺. The lifetimes of the luminescent metal-to-ligand charge transfer (MLCT) excited states were determined as a function of temperature (between −103 and 90 °C, depending on the solvent), from which were extracted the rate constants for radiative and non-radiative decay and ΔE, the energy gap between the MLCT and metal-centered (MC) excited states. The results indicate that ^*Ru(bpy)₂(pypm)²⁺ decays via a higher lying MLCT state, whereas ^*Ru(pypm)₃²⁺ and ^*Ru(pypm)₂(bpy)²⁺ decay predominantly via the MC state.     

Singlet and triplet energy transfer processes in ruthenium(II) bipyridine complexes containing covalently bound arenes

Singlet and triplet energy transfer processes in [Ru(bipy)₂(4-methyl-4′-(2-arylethyl)-2,2′-bipyridine)]²⁺ have been investigated, where ARYL = 2-naphthyl (Ru-Naph), 9-anthryl (Ru-Anth) and 1-pyrenyl (Ru-Pyrene). In each case fluorescence from the aromatic chromophore is quenched by intramolecular energy transfer to Ru(bipy)₃²⁺ whereas emission from the Ru(bipy)₃²⁺ moiety is controlled by the relative energy of its ³MLCT state and the pendant arene triplet states. Consequently ³MLCT emission is observed for Ru-Naph whereas it is fully quenched for Ru-Anth. When the two states are isoenergetic (e.g. Ru-Pyrene) a long-lived ³MLCT emission is observed which delays with the same lifetime as the pyrene triplet state (5.23 μs).     

Charge transfer photochemistry of Ru(bpz)3 with carboxylic acids and carboxylate ions

Ru(bpz)₃²⁺ (bpz = 2,2′-bipyrazine) has six peripheral uncoordinated nitrogen atoms potentially available for protonation in presence of acids. The emission from ^*Ru(bpz)₃²⁺ is efficiently quenched by organic acids and the observed quenching rate constants are explained in terms of proton transfer from acids to ^*Ru(bpz)₃²⁺. The absorption and emission intensity of Ru(bpz)₃²⁺ increases with increasing concentration of carboxylate ion suggesting the complex formation between the two reactants in the ground state. From these studies, the formation constant (K_f) have been evaluated by Benesi–Hildebrand method. The K_f values indicate that generally the ion pair association constants estimated from absorption and emission techniques are comparable and these values are sensitive to the structure of the carboxylate ions.     

Development of a triple channel detection probe for hydrogen peroxide

The rapid and reliable measurement of hydrogen peroxide (H₂O₂) is imperative for many areas of technology, including pharmaceutical, clinical, food industry and environmental applications. In this work, a novel multifunctional complex, [Ru(bpy)₂(luminol-bpy)](PF₆)₂ (bpy: 2,20'-bipyridine), was designed and synthesized by incorporating a Ru(II) complex with a luminal group. In the presence of horseradish peroxidase (HRP), reaction of [Ru(bpy)₂(luminol-bpy)]²⁺ with H₂O₂ can be monitored by three sensing channels including photoluminescence (PL), chemiluminiscence (CL) and eletrochemiluminiscence (ECL). The quantitative assays for H₂O₂ in aqueous solutions using [Ru(bpy)₂(Luminalbpy)]( PF₆)₂ as a probe were established with PL, ECL and CL signal output modes, respectively.     

Persulphate quenching of the excited state of ruthenium(II) tris-bipyridyl dication: thermal reactions

The rate constant for the reaction between the sulphate radical (SO₄^√−) and the ruthenium (II) tris-bipyridyl dication (Ru(bipy)₃²⁺) is (3.3±0.2)×10⁹ mol⁻¹ dm³ s⁻¹ in 1 mol dm⁻³ H₂SO₄ and (4.9±0.5)×10⁹ mol⁻¹ dm³ s⁻¹ in 0.1 mol dm⁻³, pH 4.7 acetate buffer. The SO₄^√−radical produced by the electron transfer quenching of Ru(bipy)₃^2+* by S₂O₈²⁻ reacts rapidly with both acetate buffer and chloride ions. These side reactions result in a reduction in the overall quantum yield of Ru(bipy)₃³⁺ production and reduced reaction selectivity when Ru(bipy)₃^2+* is quenched by persulphate.     

Electrochemiluminescent behavior of melatonin and its important derivatives in the presence of Ru(bpy)(3)(2+)

Melatonin and some of its important derivatives were found to be able to enhance the ECL of Ru(bpy)₃²⁺ in an alkaline Britton–Robinson buffer solution. The optimum conditions for the enhanced ECL, such as the selection of applied potential mode, type of buffer solution, pH effect and effect of Ru(bpy)₃²⁺ concentration have been investigated in detail in this paper. Under the optimum conditions, the enhanced ECL is linear with the concentration of melatonin and its derivatives over the wide range, and the detection limit for these compounds was found to be in the range of 5.0 × 10⁻⁸ to 1.0 × 10⁻¹⁰ mol L⁻¹. The proposed procedure was applied for the determination of drug in tablets with recoveries of 85–93%. A possible mechanism for the enhanced ECL of Ru(bpy)₃²⁺ by melatonin and its derivatives was proposed, and the relationship between molecular structure of melatonin and its derivatives and the enhanced ECL behavior was also discussed.     

Rates of virtually self-exchange energy transfer processes of ruthenium(II) polypyridine complexes

The rate constants of electronic energy transfer from the lowest excited state of Ru(bpy)₂(L)²⁺ or Ru(bpy)(L)₂²⁺ 10 Ru(L)₃²⁺ (b     

Synthesis, spectra and crystal structures of two Ru complexes with polypyridyl ligands: cis-[Ru(bpy)2(4,4′-bpy)Cl](PF6)·H2O and cis-[Ru(phen)2(CH3CN)2](PF6)2

Two mononuclear Ru^II complexes of polypyridyl ligands, cis-[Ru(bpy)₂(4,4′-bpy)Cl](PF₆)·H₂O (1) and cis-[Ru(phen)₂(CH₃CN)₂](PF₆)₂ (2) (bpy=2,2′-bipyridyl, 4,4′-bpy=4,4′-bipyridyl, and PHEN=1,10-phenanthroline), have been synthesized and characterized by elemental analyses, IR and UV–vis spectra. The crystal structures of both complexes have been determined by X-ray diffraction, indicating that each Ru^II center is hexa-coordinated (RuN₅Cl for 1 and RuN₆ for 2) and takes a distorted octahedral geometry. The favored feature of both complexes is that they are quite useful complex precursors for further constructing new functional architectures.     

Nafion–RuO2–Ru(bpy)3 composite electrodes for efficient electrocatalytic water oxidation

Electrocatalytic water oxidation to evolve O₂ was studied on a Nafion–RuO₂–Ru(bpy)₃²⁺ composite electrode. The O₂ evolution current efficiency was largely improved for the multi-component electrode over the Nafion–RuO₂ and Nafion–Ru(bpy)₃²⁺ individuals. The redox mediation through the Ru(bpy)₃²⁺ was found to dominate over the RuO₂ catalytic effect in the water oxidation mechanism. The specific surface area of the RuO₂, which was prepared at different temperatures (300–700°C), used in fabricating the composite electrode also played an important role in the overall water oxidation mechanism. Both the reaction and electrode parameters were optimized to get effective electrocatalytic current values in this study.     

Induction effects on IR-predissociation spectra of (SF6)2, (SiF4)2 and (SiH4)2

The observed difference in transition strength for (SF₆)₂, (SiF₄)₂ and (SiH₄)₂ IR-predissociation spectra is explained by induction effects (μ₀₁²/R₁₂⁶) which have to be included in the interaction Hamiltonian in addition to the dominant dipole-dipole term (μ₀₁²/R₁₂³).     

Study of the Electrochemiluminescence Based on the Reaction of p-Hydroxyphenylpyruvic Acid with Tris(2,2'-bipyridine)ruthenium(Ⅱ)

p-hydroxyphenylpyruvic acid (pHPP) is an important intermediate in the metabolism of tyrosine. Under normal circumstances pHPF is readily converted to 2,5-dihydroxyphenylacetic acid by p-hydroxy-phenylpyruvate oxidase and the levels of pHPP encountered in blood and urine are extremely low. However, in a few individuals suffering from a congenital metabolic defect known as tyrosinemia, the oxidase is not available which leads to dramatic elevation of pHPP levels in blood and urine^[1]. Therefore, a selective and sensitive method for measuring pHPT is very useful for the diagnosis and treatment of such disease. In this paper the electrochemiluminescence(ECL) based on the reaction of pHPP with tris(2,2'-bipyridine)ruthenium(Ⅱ)[Ru(bpy)₃²⁺] in a flow injection system has been studied and a sensitive ECL method has been developed to detect pHPP in aqueous solution.     

NH3R++NHR2(R=H,CH3)体系质子传递反应的从头算研究

用从头计算法在HF/6-31G^*基组水平上研究了NH₄⁺+NH₃→NH₃+NH₄⁺,NH₄⁺+NH₂CH₃→NH₃+NH₃CH₃⁺,NH₄⁺+NH(CH₃)₂→NH₃+NH₂(CH₃)₂⁺以及NH₃CH₃⁺+NH₂CH₃→NH₂CH₃+NH₃CH₃⁺等4个体系的质子传递反应的机理.结果表明:(1)上述质子传递反应均具有双阱型的势能面,质子沿N(1)、N(2)连线直接传递;(2)质子受体分子中的甲基对质子传递起促进作用,而质子给体离子中的甲基则阻碍质子的传递。     

Interaction of heterocyclic thioamides with tellurium(II) and tellurium(IV). Syntheses and crystal structures of bis[2-(2-thioxo-1,3- thiazolidin-3-yl)-4,5-dihydro-1,3- thiazolium]hexabromotellurate(IV) and tris(1- methylimidazole-2-(3H)-thione)tellurium(II) bromide

Reaction of 1,3-thiazolidine-2-thione with tellurium(IV) in hydrobromic acid medium gave the hexabromotellurate, [C₆H₉N₂S₃]₂²⁺[Te^IVBr₆]²⁻ (3). Reaction of 1-methylimidazoline-2-(3H)-thione (L″) with tellurium(IV), in hydrobromic acid medium, gave the mixed-ligand tellurium(II) complex [Te^IIL″₃Br]⁺Br⁻ (4). The structures of [C₆H₉N₂S₃]₂²⁺[Te^IVBr₆]²⁻ (3) and [Te^IIL″₃Br]⁺Br⁻ were determined by single crystal X-ray diffraction methods. In 3 the unit cell contains [TeBr₆]²⁻ anions and two [C₆H₉N₂S₃]⁺ cations. There is no direct bonding between the metal atom and the cations. In the anion only slight angular deviations from the perfect octahedral geometry are observed. The lone pair of electrons on tellurium(IV) is found to be stereochemically inert. In the cation the two five-membered heterocyclic rings adopt different conformations. In complex 4, in the solid state, the planar [Te^IIL″₃Br]⁺ cation and Br⁻ anion are held together by ionic interactions. In the cation, L″ is bonded to the central tellurium atom through the sulphur atom.     

毛细管电泳电致化学发光检测血浆中布比卡因

布比卡因是一种外科局部麻醉剂,使用过量会导致中枢神经系统和心脏血管系统中毒^[1],可引起心脏停博.高效液相色谱和毛细管电泳(CE)^[2]是该药常用的检测方法.