One-electron Oxidation Product Research Articles

Hydrogen atom abstraction as a synthetic route to a square planar CoII complex with a redox-active tetradentate PNNP ligand.

Redox-active ligands improve the reactivity of transition metal complexes by facilitating redox processes independent of the transition metal center. A tetradentate square planar (PNCH2CH2NP)CoII (1) complex was synthesized and the ethylene backbone was dehydrogenated through hydrogen atom abstraction to afford (PNCHCHNP)CoII (2), which now contains a redox-active ligand. The ligand backbone of 2 can be readily hydrogenated with H2 to regenerate 1. Reduction of 1 and 2 with KC8 in the presence of 18-crown-6 results in cobalt-based reductions to afford [(PNCH2CH2NP)CoI][K(18-crown-6)] (3) and [(PNCHCHNP)CoI][K(18-crown-6)] (4), respectively. Cyclic voltammetry revealed two reversible oxidation processes for 2, presumed to be ligand-based. Following treatment of 2 with one equivalent of FcPF6, the one-electron oxidation product {[(PNCHCHNP)CoII(THF)][PF6]}·THF (5) was obtained. Treating 5 with an additional equivalent of FcPF6 affords the two-electron oxidation product [(PNCHCHNP)CoII][PF6]2 (6). Addition of PMe3 to 5 produced [(PNCHCHNP)CoII(PMe3)][PF6] (7). A host of characterization methods including nuclear magnetic resonance (NMR) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry, magnetic susceptibility measurements using SQUID magnetometry, single-crystal X-ray diffraction, and density functional theory calculations were used to assign 5 and 6 as ligand-based oxidation products of 2.

Colorimetric and photothermal dual-mode immunosensor based on Ti3C2Tx/AuNPs nanocomposite with enhanced peroxidase-like activity for ultrasensitive detection of zearalenone in cereals.

A novel peroxidase-like nanozyme has beenconstructed by decorating two-dimensional Ti3C2Tx nanosheets (Ti3C2Tx NSs) with gold nanoparticles (AuNPs) to develop a colorimetric and photothermal dual-mode immunosensor. TheTi3C2Tx/AuNPs nanocomposite-catalyzed 3,3',5,5'-tetramethylbenzidine (TMB)-H2O2 reaction system produces the one-electron oxidation product of TMB (oxTMB), which exhibits color change and strong near-infrared (NIR) laser-driven photothermal effect at 808nm laser irradiation. Given these characteristics, the developed immunosensor achieves ultrasensitive dual-mode detection of zearalenone (ZEN) by measuring colorimetric and photothermal signals with a microplate reader and a portable infrared thermometer, respectively. Under optimal working conditions, the limit of detection (LOD) of ZEN is 0.15 pg mL-1 for thecolorimetric mode and 0.48 pg mL-1 for thephotothermal mode. Inthe analysis of actual contaminated cereals samples, the test result of this method wasconsistent with that of UPLC-MS/MS. The proposed colorimetric and photothermal dual-mode immunosensor offers a new strategy for the low-cost detection of hazardous substances. Theapplication of awidely used household infrared thermometer makes the signal readout more convenient, which provides great prospects in food safety and environment inspection applications.

Phase-Controlled Ruthenium Nanocrystals on Colloidal Polydopamine Supports and Their Catalytic Behaviors in Aerobic Oxidation Reactions.

The past decade has witnessed rapidly growing interest in noble metal nanostructures adopting unconventional metastable crystal phases. In the case of Ru, chemically synthesized nanocrystals typically form thermodynamically favored hexagonal close-packed (hcp) crystal lattices, whereas it remains significantly more challenging to synthesize Ru nanocrystals in the metastable face-centered cubic (fcc) phase. In this work, we have synthesized polydopamine (PDA)-supported hcp and fcc Ru nanocrystals in a phase-selective manner through one-pot thermal reduction of appropriate Ru(III) precursors in a polyol solvent. Benefiting from the unique surface-adhesion function of PDA, we have been able to grow phase-controlled sub-5 nm Ru nanocrystals directly on colloidal PDA supports without prefunctionalizing the particle surfaces with any molecular linkers or surface-capping ligands. Success in phase-controlled synthesis of capping ligand-free Ru nanocrystals dispersed on the same support material enables us to systematically compare the intrinsic mass-specific and surface-specific activities of fcc and hcp Ru nanocatalysts toward the aerobic oxidation of a chromogenic molecular substrate, 3,3',5,5'-tetramethylbenzidine (TMB), under a broad range of reaction conditions. We use UV-vis absorption spectroscopy to monitor the conversion of the reactant molecules into the one-electron and two-electron oxidation products in real time during Ru-catalyzed oxidation of TMB, which is found to be a mechanistically complex molecule-transforming process involving multiple elementary steps. The apparent reaction rates and detailed kinetic features are observed to be not only intimately related to the crystalline structures of the Ru nanocatalysts but also profoundly influenced by several other critical factors, such as the pH of the reaction medium, the initial concentration of TMB, Ru coverage on the PDA supports, and degree of nanoparticle aggregation.

Tonoplast cytochrome b561 is a transmembrane ascorbate-dependent monodehydroascorbate reductase: functional characterization of electron currents in plant vacuoles.

Ascorbate (Asc) is a major redox buffer of plant cells, whose antioxidant activity depends on the ratio with its one-electron oxidation product monodehydroascorbate (MDHA). The cytoplasm contains millimolar concentrations of Asc and soluble enzymes that can regenerate Asc from MDHA or fully oxidized dehydroascorbate. Also, vacuoles contain Asc, but no soluble Asc-regenerating enzymes. Here, we show that vacuoles isolated from Arabidopsis mesophyll cells contain a tonoplast electron transport system that works as a reversible, Asc-dependent transmembrane MDHA oxidoreductase. Electron currents were measured by patch-clamp on isolated vacuoles and found to depend on the availability of Asc (electron donor) and ferricyanide or MDHA (electron acceptors) on opposite sides of the tonoplast. Electron currents were catalyzed by cytochrome b561 isoform A (CYB561A), a tonoplast redox protein with cytoplasmic and luminal Asc binding sites. The Km for Asc of the luminal (4.5 mM) and cytoplasmic site (51 mM) reflected the physiological Asc concentrations in these compartments. The maximal current amplitude was similar in both directions. Mutant plants with impaired CYB561A expression showed no detectable trans-tonoplast electron currents and strong accumulation of leaf anthocyanins under excessive illumination, suggesting a redox-modulation exerted by CYB561A on the typical anthocyanin response to high-light stress.

Different delocalized ranges in mixed valence cyanido-metal-bridged Fe-Ru-Fe complexes controlled by terminal ligand substitution modification.

In order to investigate the properties of metal to metal charge transfer (MMCT) influenced by the relative energy level between the bridging unit and the terminal unit, two groups of heterotrimetallic cyanido-metal-bridged complexes, trans-[Cp(dppe)Fe-CN-Ru(MeOpy)4-NC-Fe(dppe)Cp][X]n (1[X]n; n = 2, 3, or 4; X = PF6 or BF4) (Cp = cyclopentadiene, dppe = 1,2-bis(diphenylphosphino)ethane, MeOpy = 4-methoxypyridine) and [Cp*(dppe)Fe-CN-Ru(MeOpy)4-NC-Fe(dppe)Cp*] [X]n (2[X]n; Cp* = 1,2,3,4,5-pentamethylcyclopentadiene; n = 2, 3, or 4; X = PF6 or BF4) were synthesized and fully characterized. The crystallography data suggest different oxidation sites in the ground state for one-electron oxidation products 13+ and 23+, and the electrochemical and Mössbauer spectra suggest that in the one-electron oxidation compounds 13+, the charge is delocalized all along the trimetal backbone Fe-Ru-Fe, while in 23+, the charge is rather delocalized between the two metal parts Fe-Ru. Further oxidation of N3+ gives N4+ (N = 1 or 2), during which a spin transfer towards the terminal units is observed in both series.

Synthesis and spectroscopic properties of osmium based polypyridyl compound, cis-OsII(phen)2Cl2, and its one-electron oxidation product [cis-OsIII(phen)2Cl2](PF6)

Compound 1, cis-OsII(phen)2Cl2, was obtained by reaction of (NH4)2OsCl6 with phen in ethylene glycol (phen = 1,10-phenanthroline). Cyclic voltammetry was employed to investigate the redox characteristics of 1. Based on the oxidation potential of 1, Cp2FeIII(PF6) was chosen as oxidant for the preparation of 2, [cis-Os(phen)2Cl2](PF6). Both 1 and 2 were characterized by IR, electronic absorption spectra and elemental analysis, respectively. In addition, 2 was characterized by single-crystal X-ray diffraction analysis. There exists 1MLCT and 3MLCT transition in both the electronic absorption and emission bands of 1 and 2.

Final Products of One-Electron Oxidation of Cyclic Dipeptides Containing Methionine Investigated by IRMPD Spectroscopy: Does the Free Radical Choose the Final Compound?

Reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) and the hydroxyl radical (•OH) have specific functions in biological processes, while their uncontrolled production and reactivity are known to be determining factors in pathophysiology. Methionine (Met) residues act as endogenous antioxidants, when they are oxidized into methionine sulfoxide (MetSO), thus depleting ROS and protecting the protein. We employed tandem mass spectrometry combined with IR multiple photon dissociation spectroscopy to study the oxidation induced by OH radicals produced by γ radiolysis on model cyclic dipeptides c(LMetLMet), c(LMetDMet), and c(GlyMet). Our aim was to characterize the geometries of the oxidized peptides in the gas phase and to understand the relationship between the structure of the 2-center 3-electron (2c-3e) free radical formed in the first step of the oxidation process and the final compound. Density functional theory calculations were performed to characterize the lowest energy structures of the final product of oxidation and to interpret the IR spectra. Collision-induced dissociation tandem mass spectrometry (CID-MS2) experiments of oxidized c(LMetLMet)H+ and c(LMetDMet)H+ led to the loss of one or two oxidized sulfenic acid molecules, indicating that the addition of one or two oxygen atoms occurs on the sulfur atom of both methionine side chains and no sulfone formation was observed. The CID-MS2 fragmentation mass spectrum of oxidized c(GlyMet)H+ showed only the loss of one oxidized sulfenic acid molecule. Thus, the final products of oxidation are the same regardless of the structure of the precursor sulfur-centered free radical.

How Nature Makes O2: an Electronic Level Mechanism for Water Oxidation in Photosynthesis.

In this paper, we combine broken symmetry density functional calculations and electron paramagnetic resonance analysis to obtain the electronic structure of the penultimate S3 state of nature’s water-oxidizing complex and determine the electronic pathway of O–O bond formation. Analysis of the electronic structure changes along the reaction path shows that two spin crossovers, facilitated by the geometry and magnetism of the water-oxidizing complex, are used to provide a unique low-energy pathway. The pathway is facilitated via the formation and stabilization of the [O2]3– ion. This ion is formed between ligated deprotonated substrate waters, O5 and O6, and is stabilized by antiferromagnetic interaction with the Mn ions of the complex. Combining the computational, crystallographic, and spectroscopic data, we show that an equilibrium exists between the O5 oxo and O6 hydroxo forms with an S = 3 spin state and a deprotonated O6 form containing a two-center one-electron bond in [O5O6]3– which we identify as the form detected using crystallography. This form corresponds to an S = 6 spin state which we demonstrate gives rise to a low-intensity EPR spectrum compared with the accompanying S = 3 state, making its detection via EPR difficult and overshadowed by the S = 3 form. Simulations using 70% of the S = 6 component give rise to a superior fit to the experimental W-band EPR spectral envelope compared with an S = 3 only form. Analyses of the most recent X-ray emission spectroscopy first moment changes for solution and time-resolved crystal data are also shown to support the model. The computational, crystallographic, and spectroscopic data are shown to coalesce to the same picture of a predominant S = 6 species containing the first one-electron oxidation product of two water molecules, that is, [O5O6]3–. Progression of this form to the two-electron-oxidized peroxo and three-electron-oxidized superoxo forms, leading eventually to the evolution of triplet O2, is proposed to be the pathway nature adopts to oxidize water. The study reveals the key electronic, magnetic, and structural design features of nature’s catalyst which facilitates water oxidation to O2 under ambient conditions.

Acid Catalysis in the Oxidation of Substrates by Mononuclear Manganese(III)-Aqua Complexes.

Acids are known to enhance the reactivities of metal-oxygen intermediates, such as metal-oxo, -hydroperoxo, -peroxo, and -superoxo complexes, in biomimetic oxidation reactions. Although metal-aqua (and metal-hydroxo) complexes have been shown to be potent oxidants in oxidation reactions, acid effects on the reactivities of metal-aqua complexes have never been investigated previously. In this study, a mononuclear manganese(III)-aqua complex, [(dpaq5NO2)MnIII(OH2)]2+ (1; dpaq5NO2 = 2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-ylacetamidate with an NO2 substituent at the 5 position), which is relatively stable in the presence of triflic acid (HOTf), is used in the investigation of acid-catalyzed oxidation reactions by metal-aqua complexes. As a result, we report a remarkable acid catalysis in the six-electron oxidation of anthracene by 1 in the presence of HOTf; anthraquinone is formed as the product. In the HOTf-catalyzed six-electron oxidation of anthracene by 1, the rate constant increases linearly with an increase of the HOTf concentration. Combined with the observed one-electron oxidation product, anthracene (derivative) radical cation, and the substitution effect at the 5 position of the dpaq ligand in 1 on the rate constants of the oxidation of anthracene, it is concluded that the oxidation of anthracene occurs via an acid-promoted electron transfer (APET) from anthracene to 1. The dependence of the rate constants of the APET from electron donors, including anthracene derivatives, to 1 on the driving force of electron transfer is also shown to be well fitted by the Marcus equation of outer-sphere electron transfer. To the best of our knowledge, this is the first example showing acid catalysis in the oxidation of substrates by metal(III)-aqua complexes.

Dual-mode immunoassay for diethylstilbestrol based on peroxidase activity and photothermal effect of black phosphorus-gold nanoparticle nanohybrids

Nanozyme-mediated 3,3′,5,5′-tetramethylbenzidine (TMB) - H2O2 systems have spawned the establishment of multiple colorimetric sensing platforms that are effective but sometimes subject to low sensitivity. Taking temperature as the output signal, photothermal effects lead to new strategies for sensitive detection. In this paper, a colorimetric and photothermal dual-mode immunoassay for diethylstilbestrol (DES) was constructed. It is based on the oxidation reaction of TMB catalyzed by black phosphorus-gold nanoparticle (BP/Au) nanohybrids, and the kinetics as well as catalytic mechanism of the nanohybrids were investigated in detail for the first time. Herein, the nanohybrids playcatalytic and photothermal dual roles. Moreover, the one-electron oxidation product of TMB (oxidized TMB) not only acts as chromogenic agent but also an excellent NIR laser-driven photothermal agent. The temperature (ΔT/°C) was gauged by a portable digital thermometer. Through an indirect competition strategy, a simple, sensitive, and economic immunosensor was proposed. Higher DES content in the sample correlated with less BP/Au nanohybrids conjugated to the surface of ELISA microplate, a weaker color change, and a lower temperature variation when exposed to laser irradiation. This method was applied for DES determination in real samples with gratifying recovery rates, showing great promise in food safety inspection applications.

Electrolyte-Coordination-Induced Electrochemical Multiple Electron Oxidation of 2,5-Diarylthiophenes

Chalcogenophene is a five membered aromatic ring containing group 16 elements, and widely used for the design of small molecule or polymer based organic devices. Previously, we have reported a thorough discussions on the electrochemical redox chemistry of tellurium-containing chalcogenophenes, tellurophene (N. Shida, H. Nishiyama, F. Zheng, S. Ye, D. S. Seferos, I. Tomita, S. Inagi, Communications Chemistry, 2019, 2, 124.). We found that the electrochemical oxidation of 2,5-diaryltellurophene in non-coordinating electrolyte resulted in one-electron oxidation product, while two-electron oxidation preferably proceeded in coordinating electrolyte. These results suggest that the design of electrolyte crucially affect the redox chemistry of chalcogenophenes.In this study, we report that the electrochemical redox behavior of 2,5-diarylthiophene also varies significantly depending on the coordination of the electrolyte. Specifically, we have found that the coordination of the electrolyte alters the number of electrons in the oxidation of 2,5-diarylthiophene. It was also found that the species generated by the multiple electron transfer in coordinating electrolyte showed a unique reactivity, and proceeded to an unprecedented dimerization reaction to give sulfonium salts.

The Electron Transfer Process in Mixed Valence Compounds with a Low-lying Energy Bridge in Different Oxidation States.

Mixed-valence compounds with the iso-cyanidometal-ligand bridge in different oxidation states are used as models for the investigation of the electron-transfer process. We synthesized a series of trimetallic isocyanidometal-bridged compounds with [Fe-CN-Ru-NC-Fe]n+ (n=2-4), in which the one-electron oxidation product (N3+ ) and two-electron oxidation product (N4+ ) compounds possess an isocyanidometal bridge whose energy is, respectively lower and slightly higher than the terminal metal centers energies. For the N3+ compounds, the bridge state (FeII -RuIII -FeII ) and mixed-valence states (FeIII -RuII -FeII or FeII -RuII -FeIII ) could be simultaneously observed on the IR timescale. For the N4+ compounds, as the donor becomes stronger the electron transfer bridge excited state (FeIII -RuII -FeIII ) becomes more and more stable, and even becomes ground state due to the strong electronic coupling between Fe and Ru.

Mixing concentrated sulfuric acid and diethylenetriamine at room temperature: A rapid and facile approach to synthesize fluorescent carbon polymer hollow spheres as peroxidase mimics

Fluorescent carbon polymer nanomaterials driven by their important various applications are promising, however, their scalable usages are still hindered by the lack of facile and effective synthesis approaches. Herein, a rapid and facile approach is demonstrated for the preparation of fluorescent carbon polymer hollow spheres (CPHSs), which were synthesized by directly mixing concentrated sulfuric acid (H2SO4) and diethylenetriamine (DETA) at room temperature. Notably, both the solid powders and aqueous dispersion of CPHSs possess the fluorescence properties, similar with the reported carbon polymer dots. The formation of CPHSs could be attributed to the polymerization of DETA in the presence of H2SO4. The present strategy is universal and fluorescent nanomaterials could also be obtained by using hexamethylenetetramine or polyethylenepolayamine as precursors with the aid of concentrated H2SO4. Most importantly, the CPHSs possess peroxidase-like activity and can catalyze oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to its one-electron oxidation product, providing a new method for colorimetric detection of H2O2.

Glucose detection based on the photothermal effect of OxTMB using a thermometer

Although 3,3’,5,5’-tetramethyl benzidine dihydrochloride (TMB) has been widely used as a chromogenic agent in colorimetric analysis, other characteristics of its one-electron oxidation product (oxTMB) have seldom been explored. OxTMB, which exhibits strong photothermal effect under near-infrared light, can transform the analysis signal into heat with a pen-style digital thermometer as the signal reader. Therefore, oxTMB has the potential for simple and instrument-free analyses. Based on the photothermal effect of oxTMB, a simple but sensitive photothermal assay is developed for glucose detection with a linear range of 5–300 μM. The calculated limit of detection (LOD) for glucose was 0.13 μM. Considering that thermometers are widely used in instrument-free analyses, the proposed photothermal method may provide a more affordable way to detect biomarkers associated with biological diseases.

Independent Generation and Reactivity of 2'-Deoxyguanosin-N1-yl Radical.

2'-Deoxyguanosin-N1-yl radical (dG(N1-H)•) is the thermodynamically favored one-electron oxidation product of 2'-deoxyguanosine (dG), the most readily oxidized native nucleoside. dG(N1-H)• is produced by the formal dehydration of a hydroxyl radical adduct of dG as well as by deprotonation of the corresponding radical cation. dG(N1-H)• were formed as a result of the indirect and direct effects of ionizing radiation, among other DNA damaging agents. dG(N1-H)• was generated photochemically (λmax = 350 nm) from an N-aryloxy-naphthalimide precursor (3). The quantum yield for photochemical conversion of 3 is ∼0.03 and decreases significantly in the presence O2, suggesting that bond scission occurs from a triplet excited state. dG is formed quantitatively in the presence of excess β-mercaptoethanol. In the absence of a reducing agent, dG(N1-H)• oxidizes 3, decreasing the dG yield to ∼50%. Addition of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) as a sacrificial reductant results in a quantitative yield of dG and two-electron oxidation products of 8-oxodGuo. N-Aryloxy-naphthalimide 3 is an efficient and high-yielding photochemical precursor of dG(N1-H)• that will facilitate mechanistic studies on the reactivity of this important reactive intermediate involved in DNA damage.

4-Cl-edaravone and (E)-2-chloro-3-[(E)-phenyldiazenyl]-2-butenoic acid are the specific reaction products of edaravone with hypochlorite.

3-Methyl-1-phenyl-2-pyrazolin-5-one (edaravone) is a synthetic one-electron antioxidant used as a drug for treatment against acute phase cerebral infarction in Japan. This drug also reacts with two-electron oxidants like peroxynitrite to give predominantly 4-nitrosoedaravone but no one-electron oxidation products. It is believed that this plays a significant role in amelioration of amyotrophic lateral sclerosis. The drug was approved for treatment of amyotrophic lateral sclerosis in Japan and USA in 2015 and 2017, respectively. In this study, we examined the reaction of edaravone with another two-electron oxidant, hypochlorite anion (ClO−). Edaravone reacted with ClO− in 50% methanolic phosphate buffer (pH 7.4) solution containing typical two-electron reductants, such as glutathione, cysteine, methionine, and uric acid, as internal references. The concentration of edaravone decreased at a similar rate as each co-existing reference, indicating that it showed comparable reactivity toward ClO− as those references. Furthermore, 4-Cl-edaravone and (E)-2-chloro-3-[(E)-phenyldiazenyl]-2-butenoic acid (CPB) were identified as primary and end products, respectively, and no one-electron oxidation products were detected. These results suggest that edaravone treatment can bring greater benefit against ClO−-related injury such as inflammation, and 4-Cl-edaravone and CPB can be good biomarkers for ClO−-induced oxidative stress.

Syntheses, crystal structures and MMCT properties of cyanide-bridged binuclear Ru–Fe complexes

In this report, two new binuclear mixed-valence (MV) compounds and their one-electron oxidation products, [MeCpLRu(μ-CN)Fe(dppe)Cp][PF6]n (L = dppe, (PPh3)2) (n = 1, 2), were synthesized and thoroughly characterized by single-crystal X-ray diffraction analysis. Complexes 12+ and 22+ are one-electron oxidation products of 11+ and 2+, respectively. The electronic absorption results indicate that there exists metal to metal charge transfer (MMCT) in the one-electron oxidation products, which is strongly supported by the theoretical calculations. Complexes 12+ and 22+ can be defined as Class II MV compounds. It is found that the MMCT band is obviously red-shifted on going from 12+ to 22+, because the donating electron ability of (PPh3)2 is stronger than that of dppe.

Oxidative Addition of Dihydrogen, Boron Compounds, and Aryl Halides to a Cobalt(I) Cation Supported by a Strong-Field Pincer Ligand.

Cationic cobalt(I) dinitrogen complexes with a strong-field tridentate pincer ligand were prepared and the oxidative addition of polar and non-polar bonds was studied. Addition of H2 to [(iPrPNP)Co(N2)]+ (iPrPNP = 2,6-bis((diisopropylphosphaneyl)methyl)pyridine) in THF-d8 resulted in rapid oxidative addition and formation of the cis-Co(III) dihydride complex, cis-[(iPrPNP)Co(H)2L]+ where L = THF or N2. The addition of H2 was reversible as evidenced by the dynamics observed by variable temperature 1H NMR spectroscopy and the regeneration of [(iPrPNP)Co(N2)]+ upon exposure to dinitrogen. In contrast, addition of HBPin, (Pin = pinacolato) B2Pin2 and aryl halides resulted in the formation of net one-electron oxidation products: cationic Co(II)-boryl and Co(II)-halide/aryl complexes, respectively. All products were structurally characterized by X-ray crystallography and the electronic structures were determined by a combination of magnetic moment measurements, EPR spectroscopy and DFT calculations. Monitoring the addition of HBPin to [(iPrPNP)Co(N2)]+ provided evidence for a transient Co(III) oxidative addition product that likely undergoes comproportionation with the cobalt(I) starting material to generate the observed Co(II) products.

Different Degrees of Electron Delocalization in Mixed Valence Ru-Ru-Ru Compounds by Cyanido-/Isocyanido-Bridge Isomerism.

The two stable pairs of trimetallic compounds trans-[Cp*(dppe)Ru(μ-NC)Ru(dmap)4 (μ-CN)Ru(dppe)Cp*][PF6 ]n (1[PF6 ]n , n=2, 3; Cp*=1,2,3,4,5-pentamethylcyclopentadiene; dppe=1,2-bis-(diphenylphosphino)ethane; dmap= 4-dimethylaminopyridine) and trans-[Cp*(dppe)Ru(μ-CN)Ru(dmap)4 (μ-NC)Ru(dppe)Cp*][PF6 ]n (2[PF6 ]n , n=2, 3), which demonstrate cyanide/isocyanide isomerism, have been synthesized and fully characterized. 13+ [PF6 ]3 and 23+ [PF6 ]3 are the one-electron oxidation products of 12+ [PF6 ]2 and 22+ [PF6 ]2 , respectively. The results suggest that 1[PF6 ]3 is a class III mixed valence compound, whereas 2[PF6 ]3 might be an unusually symmetrical class II-III mixed valence compound composed of the two asymmetrical delocalized RuIII -NC-RuII mixed valence subunits.

Exploration of Nanoparticle-Mediated Photothermal Effect of TMB-H2O2 Colorimetric System and Its Application in a Visual Quantitative Photothermal Immunoassay.

The exploration of new physical and chemical properties of materials and their innovative application in different fields are of great importance to advance analytical chemistry, material science, and other important fields. Herein, we, for the first time, discovered the photothermal effect of an iron oxide nanoparticles (NPs)-mediated TMB (3,3',5,5'-tetramethylbenzidine)-H2O2 colorimetric system, and applied it toward the development of a new NP-mediated photothermal immunoassay platform for visual quantitative biomolecule detection using a thermometer as the signal reader. Using a sandwich-type proof-of-concept immunoassay, we found that the charge transfer complex of the iron oxide NPs-mediated one-electron oxidation product of TMB (oxidized TMB) exhibited not only color changes, but also a strong near-infrared (NIR) laser-driven photothermal effect. Hence, oxidized TMB was explored as a new sensitive photothermal probe to convert the immunoassay signal into heat through the near-infrared laser-driven photothermal effect, enabling simple photothermal immunoassay using a thermometer. Based on the new iron oxide NPs-mediated TMB-H2O2 photothermal immunoassay platform, prostate-specific antigen (PSA) as a model biomarker can be detected at a concentration as low as 1.0 ng·mL-1 in normal human serum. The discovered photothermal effect of the colorimetric system and the developed new photothermal immunoassay platform open up a new horizon for affordable detection of disease biomarkers and have great potential for other important material and biomedical applications of interest.