Electrogenerated chemiluminescence of (bis-bipyridyl)ruthenium(II) acetylacetonate complexes

The synthesis, electrochemistry, spectroscopy and electrogenerated chemiluminescence (ECL) of five bis-bipyridine ruthenium(II) complexes containing acetylacetonate complexes are reported. More specifically, (bpy)₂Ru(BA)₂(PF₆) (bpy = 2,2′-bipyridine; BA = benzoylacetonate), (bpy)₂Ru(TTFA)(PF₆) (TTFA =  thenoyltrifluoroacetonate), (bpy)₂Ru(TFPB)(PF₆) (TFPB = 4,4,4-trifluoro-1-phenyl-1,3-butanedionate), (bpy)₂Ru(TFPD)(PF₆) (TFPD =  1,1,1-trifluoro-2-4-pentanedionate), and (bpy)₂Ru(DBM)(PF₆) (DBM = dibenzoylmethide) display UV-Vis, photoluminescence, electrochemical and ECL properties characteristic of ruthenium bipyridyl complexes. All complexes display absorptions in the UV and visible regions of the spectra, with visible absorptions ranging from 350 to 700 nm, typical of metal-to-ligand charge transfer (MLCT) transitions. Photoluminescence emission maxima are also characteristic of MLCT transitions with wavelength maxima from 575 to 600 nm depending on the nature of the acetylacetonate ligand. ECL efficiencies for the complexes (?_ecl ∼ 0.013-0.051) are much lower than a standard (?_ecl = 1) with electron-withdrawing substituents resulting in lower efficiencies.     

Photoluminescence and electrogenerated chemiluminescence of a bis(bipyridyl)ruthenium(II)-porphyrin complex

The photoluminescence (PL) and electrogenerated chemiluminescence (ECL) of [H₂(MPy3,4DMPP)Ru(bpy)₂Cl](PF₆), where H₂MPy3,4DMPP = meso-tris-3,4-dimethoxyphenyl-mono-(4-pyridyl)porphyrin and bpy = 2,2′-bipyridine, are reported in acetonitrile. The compound has a complex absorbance spectrum with bands characteristic of both the porphyrin and ruthenium moieties. PL emission maxim are observed at 655 nm when excited at the maximum absorption intensity corresponding to the porphyrin Soret π → π^∗ band, and around 600 nm when excited at wavelengths corresponding to Ru(dπ)-bpy (π^∗) MLCT transition. The photoluminescence efficiency (?_em) of the 655 nm emission is 0.039 and that of the free porphyrin is 0.69 compared to at 0.042.[H₂(MPy3,4DMPP)Ru(bpy)₂Cl](PF₆) displays complex electrochemical behavior, with one electrochemically reversible Ru^II-Ru^III oxidation and two quasi-reversible waves at more cathodic potentials corresponding to the porphyrin moiety. Oxidative ECL was generated using the coreactant tri-n-propylamine (TPrA). ECL efficiencies (?_ecl) were 0.14 for [H₂(MPy3,4DMPP)Ru(bpy)₂Cl]⁺ and 0.099 for H₂MPy3,4DMPP using as the standard (?_ecl = 1). ECL intensity was linear with respect to concentration from 1 to 0.001 μM.The ECL intensity peaks at potentials corresponding to oxidation both the ruthenium and porphyrin moieties as well as TPrA, indicating that multiple pathways for formation of the excited state are possible. However, an ECL spectrum shows a band similar in energy and shape to that of the Soret emission (655 nm for the PL and 656 nm for the ECL, respectively), indicating the same excited state is formed in each experiment.     

Electrogenerated chemiluminescence of Pb(II)-bromide complexes

The electrochemistry and electrogenerated chemiluminescence (ECL) of Pb₄Br₁₁ ³⁻ in acetonitrile solution is reported. Pb₄Br₁₁ ³⁻ is formed in situ by the reaction of lead(II) and bromide ions with ECL generated upon sweep to positive potentials using tri-n-propylamine (TPrA) as an oxidative-reductive coreactant. An ECL efficiency (φ_ecl) of 0.0079 was obtained compared to Ir(ppy)₃ (ppy=2-phenylpyridine; φ_ecl=1). The ECL intensity peaks at a potential corresponding to oxidation of TPrA and Pb₄Br₁₁ ³⁻ indicating that emission is from the lead-bromide cluster.     

Electrogenerated chemiluminescence of tris(2‐phenylpyridine)iridium(III) in water,acetonitrile and trifluorethanol

The spectroscopic, electrochemical and coreactant electrogenerated chemiluminescence (ECL) properties of Ir(ppy)3 (where ppy = 2‐phenylpyridine) have been obtained in aqueous buffered (KH2PO4), 50 : 50 (v/v) acetonitrile–aqueous buffered (MeCN–KH2PO4) and 30% trifluoroethanol (TFE) solutions. Tri‐n‐propylamine was used as the oxidative‐reductive ECL coreactant. The photoluminescence (PL) efficiency (ϕem) of Ir(ppy)3 in TFE (ϕem ≈ 0.029) was slightly higher than in 50 : 50 MeCN–KH2PO4 (ϕem ≈ 0.0021) and water (ϕem ≈ 0.00016) compared to a Ru(bpy)32+ standard solution in water (Φem ≈ 0.042). PL and ECL emission spectra were nearly identical in all three solvents, with dual emission maxima at 510 and 530 nm. The similarity between the ECL and PL spectra indicate that the same excited state is probably formed in both experiments. ECL efficiencies (ϕecl) in 30% TFE solution (ϕecl = 0.0098) were higher than aqueous solution (ϕecl = 0.00092) system yet lower than a 50% MeCN–KH2PO4 solution (ϕecl = 0.0091). Copyright © 2014 John Wiley & Sons, Ltd.     

Electrogenerated chemiluminescence of the platinum (II) octaethylporphyrin/tri-n-propylamine system

The electrogenerated chemiluminescence (ECL) of platinum (II) octaethyl-porphyrin (PtOEP) in acetonitrile:methylene chloride (CH₃CN:CH₂Cl₂, 50:50 v/v) and CH₂Cl₂ is reported. ECL was generated upon sweep to positive potentials using tri-n-propylamine (TPrA) as an oxidative-reductive coreactant. ECL efficiencies (?_ecl) of 0.18 in CH₃CN:CH₂Cl₂ (50:50 v/v) and 3.90 in methylene chloride were obtained using Ru(bpy)₃(PF₆)₂ (bpy = 2,2′-bipyridine) as a relative standard (?_ecl = 1). The ECL intensity peaks at a potential corresponding to oxidation of PtOEP and TPrA, and ECL emission spectra are nearly identical to photoluminescence emission spectra, indicating that emission is from the PtOEP triplet state.     

Sonochemical synthesis of Ag nanoclusters: electrogenerated chemiluminescence determination of dopamine

We report a facile one‐pot sonochemical approach to preparing highly water‐soluble Ag nanoclusters (NCs) using bovine serum albumin as a stabilizing agent and reducing agent in aqueous solution. Intensive electrogenerated chemiluminescence (ECL) was observed from the as‐prepared Ag (NCs) and successfully applied for the ECL detection of dopamine with high sensitivity and a wide detection range. A possible ECL mechanism is proposed for the preparation of Ag NCs. With this method, the dopamine concentration was determined in the range of 8.3 × 10^–9 to 8.3 × 10^–7 mol/L without the obvious interference of uric acid, ascorbic acid and some other neurotransmitters, such as serotonin, epinephrine and norepinephrine, and the detection limit was 9.2 × 10^–10 mol/L at a signal/noise ratio of 3. Copyright © 2013 John Wiley & Sons, Ltd.     

Electrogenerated chemiluminescence from osmium(II) polypyridine carbonyl chloride systems

The spectroscopy, electrochemistry and electrogenerated chemiluminescence (ECL) of four osmium(II) phenanthroline carbonyl chloride complexes are reported. Three of these compounds also contain diphosphine chelating ligands. ECL is generated in acetonitrile solutions with tri-n-propylamine (TPrA) as an oxidative-reductive coreactant. ECL efficiencies (?_ecl = photons emitted per redox event) between 0.011 and 0.13 were obtained in air saturated and deoxygenated solutions with Ru(bpy)₃²⁺ (bpy = 2,2′-bipyridine) as a relative standard (?_ecl = 1). The ECL intensity peaks at a potential corresponding to oxidation of both TPrA and the osmium systems, while ECL spectra (obtained using absorption filters) are similar to photoluminescence spectra, indicating that emission is from the excited states of the osmium complexes.     

Flow‐injection chemiluminescence and electrogenerated chemiluminescence determination of escitalopram oxalate in tablet form

Rapid, simple and highly sensitive flow‐injection (FI) chemiluminescence (CL) and flow‐injection electrogenerated chemiluminescence (ECL) methods were developed for the determination of escitalopram oxalate (ESC), a selective serotonin reuptake inhibitor used as an antidepressant drug. The CL method was based on the CL reaction of ESC with acidic cerium(IV) and tris(2,2'‐bipyridyl)ruthenium(II) (Ru). Various experimental parameters affecting CL intensity were carefully studied and optimised. The method enabled the determination of 0.001‐50 µg/mL of ESC in bulk form with a correlation coefficient r = 0.9999. The limit of detection (LOD) was 0.01 ng/mL (S/N = 3). The ECL method was based on the ECL reaction of Ru with the drug in an acidic medium, permitting the determination of ESC in the range of 0.00001‐70 µg/mL with r = 0.9999 and LOD of 1 x 10^‐4 ng/mL. The proposed methods were applied to the determination of ESC in commercial tablets. The results were compared statistically with those obtained from a published method using t‐ and F‐tests. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of norfloxacin using a terbium-sensitized electrogenerated chemiluminescence method.

A simple electrogenerated chemiluminescence (ECL) analysis method for the determination of norfloxacin (NFLX) is reported. It is based on ECL produced by Na(2)SO(3), which is sensitized by the Tb-NFLX complex. The relative ECL intensity of the Tb(3+)-NFLX-Na(2)SO(3) system is proportional to the amount of NFLX. The optimized experimental conditions were investigated. The linear range and detection limit for NFLX were 1.0 x 10(-10)-8.0 x 10(-7) mol/L and 2.8 x 10(-11) mol/L, respectively. This method was successfully applied to the determination of NFLX in a capsule. NFLX in urine can be directly detected without pretreatment or separation.     

Electrogenerated chemiluminescence ethanol biosensor based on alcohol dehydrogenase functionalized Ru(bpy)3 doped silica nanoparticles

An ethanol biosensor, based on the electrogenerated chemiluminescence of Ru(bpy)₃²⁺-doped silica nanoparticles (RuSiNPs), was investigated in this study. The biosensor was a modified glassy carbon electrode, where alcohol dehydrogenase was crosslinked to RuSiNPs, and then immobilized on the electrode surface using chitosan. The results indicated that the biosensor exhibited excellent performance during ethanol determination with a wide linear range (10⁻⁷ to 10⁻² M), low detection limit (5.0 × 10⁻⁸ M) and good stability.     

Determination of trimethylamine in fish by capillary electrophoresis with electrogenerated tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence detection.

A capillary electrophoresis with electrogenerated chemiluminescence (CE-ECL) method for the determination of trimethylamine (TMA) in fish was studied. In the presence of TMA, ECL from the reaction of analyte and in situ generated tris(2,2'-bipyridyl)ruthenium(III) [Ru(bpy)(3) (3+)] at electrode surface could be produced. The ECL detection was performed using a Pt working electrode biased at 1.23 V (vs. Ag/AgCl) potential in a 10 mmol/L sodium borate buffer solution, pH 9.2, containing 3 mmol/L Ru(bpy)(3) (2+). A linear calibration curve (correlation coefficient = 0.9996) was obtained in the range 8 x 10(-5)-4 x 10(-8) mol/L for TMA concentration. Recoveries obtained were in the range 98.78-101.46%. The method was successfully applied for the assay of TMA in fish, in combination with solid phase extraction (SPE) disks for sample clean-up and enrichment.     

Electrogenerated chemiluminescence properties of bisalicylideneethylenediamino (salen) metal complexes

The spectroscopy, electrochemistry and electrogenerated chemiluminescence (ECL) of eight bisalicylideneethylenediamino (salen) metal complexes are reported. Two of the complexes contain an unsubstituted salen ligand and either cobalt(II) or nickel(II). The others have 1,2-cyclohexanediamonio-N,N′-bis(3,5-di-t-butylsalicylidene) as the ligand, and chromium(III), aluminum(III), cobalt(II), cobalt(III) or manganese(II) as the metal center. The complexes have lowest energy absorption maxima between 350 and 430 nm. When excited at these wavelengths, the complexes emit between 417 and 594 nm in acetonitrile. Photoluminescence efficiencies (?_em) were between 0.0310 and 23.8 compared to Ru(bpy)₃²⁺ (bpy = 2,2′-bipyridine; ?_em = 1), with the aluminum complexes displaying the most intense photoluminescence. Both reversible and irreversible oxidative electrochemistry is displayed by the metal–salen complexes with oxidation potentials ranging between +0.152 and +1.661 V versus Ag/AgCl. The ECL intensity peaks at a potential corresponding to oxidation of both TPrA and the salen systems, indicating that both are involved in the ECL reaction sequence. ECL efficiencies (?_ecl) were between 0.0018 and 0.0086 when compared to Ru(bpy)₃²⁺ (?_ecl = 1) in acetonitrile (0.05 M tri-n-propylamine (TPrA) as an oxidative–reductive ECL coreactant). Also, qualitative studies using transmission filters suggest that the complexes emit ECL in approximately the same region as their photoluminescence, indicating that the same excited state is formed in both experiments.     

Combined arene ruthenium porphyrins as chemotherapeutics and photosensitizers for cancer therapy

Mononuclear 5-(4-pyridyl)-10,15,20-triphenylporphyrin and 5-(3-pyridyl)-10,15,20-triphenylporphyrin as well as tetranuclear 5,10,15,20-tetra(4-pyridyl)porphyrin (tetra-4-pp) and 5,10,15,20-tetra(3-pyridyl)porphyrin) (tetra-3-pp) arene ruthenium(II) derivatives (arene is C₆H₅Me or p-Pr ⁱ C₆H₄Me) were prepared and evaluated as potential dual photosensitizers and chemotherapeutics in human Me300 melanoma cells. In the absence of light, all tetranuclear complexes were cytotoxic (IC₅₀ ≤ 20 μM), while the mononuclear derivatives were not (IC₅₀ ≥ 100 μM). Kinetic studies of tritiated thymidine and tritiated leucine incorporations in cells exposed to a low concentration (5 μM) of tetranuclear p-cymene derivatives demonstrated a rapid inhibition of DNA synthesis, while protein synthesis was inhibited only later, suggesting arene ruthenium–DNA interactions as the initial cytotoxic process. All complexes exhibited phototoxicities toward melanoma cells when exposed to laser light of 652 nm. At low concentration (5 μM), LD₅₀ of the mononuclear derivatives was between 5 and 10 J/cm², while for the tetranuclear derivatives LD₅₀ was approximately 2.5 J/cm² for the [Ru₄(η⁶-arene)₄(tetra-4-pp)Cl₈] complexes and less than 0.5 J/cm² for the [Ru₄(η⁶-arene)₄(tetra-3-pp)Cl₈] complexes. Examination of cells under a fluorescence microscope revealed the [Ru₄(η⁶-arene)₄(tetra-4-pp)Cl₈] complexes as cytoplasmic aggregates, whereas the [Ru₄(η⁶-arene)₄(tetra-3-pp)Cl₈] complexes were homogenously dispersed in the cytoplasm. Thus, these complexes present a dual synergistic effect with good properties of both the arene ruthenium chemotherapeutics and the porphyrin photosensitizer.     

Study of the spectroscopic and electrochemical properties of tetraruthenated porphyrins by theoretical-experimental approach

The spectroscopic and electrochemical properties of two isomeric forms of the supramolecular species [μ-(H₂TPyP){Ru(bpy)₂Cl}₄]⁴⁺ (H₂TPyP = 5,10,15,20-tetra(3- or 4-pyridyl)porphyrin, bpy = 2,2′-bipyridine) have been compared and consistently interpreted with the aid of molecular orbital calculations. In these complexes, the HOMO and LUMO levels are predominantly localized in the ruthenium complexes and porphyrin ring, respectively. There is an extensive mixing of the wave functions of both components in other MOs, however, and their contributions are reflected in the spectroelectrochemical and spectroscopic behavior. For example, the electronic mixing is enough to allow the energy-transfer from the peripheral complexes to the porphyrin ring, as well as the appearance of a Ru^II(dπ) → H₄P(pπ*) charge-transfer band at 700 nm in the bis-protonated [μ-(H₄TPyP){Ru(bpy)₂Cl}₄]⁴⁺ species, showing the strong stabilization of the porphyrin LUMO levels.     

Determination of folic acid by high‐performance liquid chromatography with direct electrogenerated chemiluminescence reaction

In our present work, it was found that the electrooxidation of folic acid (FA) was accompanied by electrogenerated chemiluminescence (ECL) emission. Out of the four inorganic salts, NaNO₃ solution was found to be a suitable supporting electrolyte for the ECL emission of FA. Coupled with high‐performance liquid chromatography separation, this simple ECL method was used for post‐column determination of FA. Under the optimal conditions, the ECL intensity has a linear relationship with the concentration of FA in the range of 1.0 × 10^?7 to 1.0 × 10^?5 g/mL and the detection limit was 5 × 10^?8 g/mL (signal‐to‐noise ratio = 3). Application of the present method to the analysis of FA in human urine proved feasible. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis, characterization and electrode adsorption studies of porphyrins coordinated to ruthenium(II) polypyridyl complexes

Two new porphyrins, meso-tris-3,4-dimethoxyphenyl-mono-(4-pyridyl)porphyrin (H₂MPy3,4DMPP) and meso-tris-3-methoxy-4-hydroxyphenyl-mono-(4-pyridyl)porphyrin (H₂MPy3M4HPP), and their ruthenium analogs obtained by coordination of [Ru(bpy)₂Cl]⁺ groups (where bpy = 2,2′-bipyridine) to the pyridyl nitrogens have been synthesized and studied by electronic absorption spectroscopy, cyclic voltammetry and spectroelectrochemistry. These ruthenated porphyrins couple Ru chromophores to porphyrins containing electroactive meso-substituents. The highest energy electronic absorption for the ruthenated complexes is assigned as a bpy(π) → bpy(π*) intraligand charge transfer while the next lowest energy electronic absorption is assigned as Ru(dπ) → bpy(π*) metal-to-ligand charge transfer (MLCT) transition. The Ru^III/II couples occur at approximately 0.95 V versus the SHE reference electrode in acetonitrile solutions. The first oxidation of the porphyrin is localized on the 3,4-dimethoxyphenyl and 3-methoxy-4-hydroxyphenyl substituents, respectively. Electroactive surfaces result from adsorption of these compounds onto glassy carbon electrodes followed by anodic cycling in acidic media.     

Graphene‐amplified electrogenerated chemiluminescence of CdTe quantum dots for H2O2 sensing

Electrogenerated chemiluminescence (ECL) of thiol‐capped CdTe quantum dots (QDs) in aqueous solution was greatly enhanced by PDDA‐protected graphene (P‐GR) film that were used for the sensitive detection of H₂O₂. When the potential was cycled between 0 and ?2.3 V, two ECL peaks were observed at ?1.1 (ECL‐1) and ?1.4 V (ECL‐2) in pH 11.0, 0.1 M phosphate buffer solution (PBS), respectively. The electron‐transfer reaction between individual electrochemically‐reduced CdTe nanocrystal species and oxidant coreactants (H₂O₂ or reduced dissolved oxygen) led to the production of ECL‐1. While mass nanocrystals packed densely in the film were reduced electrochemically, assembly of reduced nanocrystal species reacted with coreactants to produce an ECL‐2 signal. ECL‐1 showed higher sensitivity for the detection of H₂O₂ concentrations than that of ECL‐2. Further, P‐GR film not only enhanced ECL intensity of CdTe QDs but also decreased its onset potential. Thus, a novel CdTe QDs ECL sensor was developed for sensing H₂O₂. Light intensity was linearly proportional to the concentration of H₂O₂ between 1.0 × 10^?5 and 2.0 x 10^‐7 mol L^?1 with a detection limit of 9.8 x 10^?8 mol L^?1. The P‐GR thin‐film modified glassy carbon electrode (GCE) displayed acceptable reproducibility and long‐term stability. Copyright © 2012 John Wiley & Sons, Ltd.     

Electrogenerated chemiluminescence from violanthrone

Violanthrone, an emitter of exceptionally bright chemiluminescence, was examined in dimethylformamide solution to determine whether it also emits particularly bright electrogenerated chemiluminescence (ECL). The ECL measurements were carried out using a cycled potential which was applied to platinum electrodes. At the maximum sweep rate of 80 Vs^?1 available, the intensity of the violanthrone ECL was still increasing with sweep rate and was c. 56% of that from rubrene, a bright, commonly used emitter of ECL. Furthermore, assuming that the emission arises from radical anioncation recombination, the sweep rate dependence showed that the least stable radical ion (probably the cation) decays with a half-life shorter than 0.2s.     

Simple chemiluminescence determination of ketotifen using tris(1,10 phenanthroline)ruthenium(II)‐ Ce(IV) system

A new method using chemiluminescence (CL) detection has been developed for the simple determination of ketotifen fumarate (KF). The method is based on the catalytic effect of KF in the CL reaction of tris(1,10 phenanthroline)ruthenium(II), Ru(phen)₃²⁺, with Ce(IV) in sulfuric acid medium. The CL response was detected using a lab‐made chemiluminometer. Effects of chemical variables were investigated and under optimum conditions, the CL intensity was proportional to the concentration of the drug over the range 0.34‐34.00 µg mL^?1 KF. The limit of detection (S/N=3) was 0.09 µg mL^?1. Effects of common ingredients were investigated and the method was applied successfully for determining KF in pharmaceutical formulations and human plasma. The percent of relative standard deviation (n=11) at level of 3.4 µg mL^?1 of KF was 4.6% and the minimum sampling rate was 70 samples per hour. The possible CL mechanism is proposed based on the kinetic characteristic of the CL reaction, CL spectrum, UV‐Vis and phosphorescence spectra. Copyright © 2015 John Wiley & Sons, Ltd.     

Homogeneous electrogenerated chemiluminescence immunoassay for the determination of digoxin employing Ru(bpy)(2)(dcbpy)NHS and carrier protein.

A highly sensitive homogeneous electrogenerated chemiluminescence (ECL) immunoassay for the determination of anti-digoxin antibody and digoxin hapten was developed employing Ru(bpy)(2)(dcbpy)NHS (bpy = 2,2'-bipyridyl; dcbpy = 2,2'-bipyridine-4,4'-dicarboxylic acid; NHS = N-hydroxysuccinimide ester) as an electrochemiluminescent label and bovine serum albumin (BSA) as a carrier protein. A digoxin hapten was indirectly heavily labelled with Ru(bpy)(2)(dcbpy)NHS through BSA to form Ru(bpy)(2)(dcbpy)NHS-BSA-digoxin conjugate. The ECL intensity of the immunocomplex of the conjugate with anti-digoxin antibody markedly decreased when the immunoreaction between Ru(bpy)(2)(dcbpy)NHS-BSA-digoxin conjugate and anti-digoxin antibody took place. Two formats, direct homogeneous immunoassay for anti-digoxin antibody and competitive immunoassay for digoxin, were developed to determine anti-digoxin antibody and digoxin, respectively. The anti-digoxin antibody concentration in the range 7.6 x 10(-8)-7.6 x 10(-6) g/mL was determined by direct homogeneous format. Digoxin hapten was determined throughout the range 4.0 x 10(-10)-1.0 x 10(-7) g/mL with a detection limit of 1.0 x 10(-10) g/mL by competitive format. The relative standard derivation for 6.0 x 10(-9) g/mL was 4.3%. The method has been applied to assaying digoxin in control human serum.