Presence Of HClO4 Research Articles

Novel fluorescence probe for ClO− in living cells: Based on FRET mechanism

Hypochlorous acid (HClO) as a kind of reactive oxygen species (ROS) plays a vital role in many biological processes. Organic fluorescence probes have attracted great interests for the detection of HClO, due to their relatively high selectivity and sensitivity, satisfactory spatiotemporal resolution and good biocompatibility. Constructing fluorescence probes to detect HClO with advantages of large Stokes shift, wide emission gap, near infrared emission and good water solubility is still challenging. In this work, a new ratiometric fluorescence probe (named HCY) for HClO was developed. FRET-based HCY was constructed by bonding a coumarin and a flavone fluorophore. In absence of HClO, HCY exists FRET process, however, FRET is inhibited in the presence of HClO because the conjugated double bond broke. Due to the good match of the emission spectrum of the donor and the absorption spectrum of the acceptor, the FRET system appears favorable energy transfer efficiency. HCY showed high sensitivity and rapid response time. The linearity between the ratios of fluorescence intensity and concentration of HClO was established with a low limit of detection. What’s more, HCY was also applied for fluorescence images of HClO in RAW264.7 cells.

An Oxidative Cleavage-Based Cruciform DNA Nanostructure for In Vivo Hypochlorous Acid Visualization to Monitor Intestinal Inflammation.

Ulcerative colitis is a persistent inflammatory bowel disease characterized by inflammation and ulceration in the colon and gastrointestinal tract. It was indicated that the generation of hypochlorous acid (HClO) through the enzymatic activity of myeloperoxidase is significantly linked to ulcerative colitis. In this study, by assembling two hairpins (Hpa and Hpb) onto a quadrivalent cruciform DNA nanostructure, a novel HClO-activatable fluorescent probe was developed based on DNA nanomaterials (denoted MHDNA), which is sensitive, economic, simple, and stable. In the presence of HClO, the Trigger (T) was liberated from the MHDNA probe through a hydrolysis reaction between HClO and phosphorothioate (PS), which is modified on the MHDNA probe and has proved to exhibit particular susceptibility to the HClO. The liberated T subsequently initiated the opening of Hpa and Hpb to facilitate the catalyzed hairpin assembly (CHA) reaction, resulting in the changes of fluorescence and releasing T for recycled signal amplification to achieve sensitive detection of HClO (with a limit of detection 9.83 nM). Additionally, the MHDNA-based spatial-confinement effect shortens the physical distance between Hpa and Hpb and yields a high local concentration of the two reactive hairpins, achieving more rapid reaction kinetics in comparison to conventional CHA methods. Inspirationally, the MHDNA probe was effectively utilized for imaging HClO in ulcerative colitis mice, yielding valuable diagnostic insights for ulcerative colitis.

The electrocatalytic hydrogen evolution reaction in the presence of a metal-free organic catalyst based on 1,10-phenanthroline: the first example of a reaction proceeding by an intramolecular mechanism

This article presents data on the electrocatalytic activity of new members of the metal-free electrocatalyst family, 1,10-phenathroline and N-methyl-1,10-phenathrolium iodide, for the hydrogen evolution reaction in the presence of HClO4 and CF3COOH.

Phenothiazine/xanthene-based fluorescent probes for trace and real-time detection of HClO in cells and complex environmental water samples

Hypochlorous acid (HClO) is a vital bioactive molecule. Abnormal levels of HClO can affect the body's immune system and pathological processes, leading to many diseases such as kidney disease and neurodegenerative diseases. Therefore, it is very important and necessary to develop a rapid and sensitive HClO detection method. In this work, we propose a novel phenothiazine-xanthene fluorophore, which has flexible adjustability and outstanding responsiveness to HClO. Using phenothiazine-xanthene fluorophore, a “turn-on” probe 7-ethyl-1,2,3,7-tetrahydrochromeno[2,3-b]phenothiazine-4-carbaldehyde (PTZ-CHO) was designed and synthesized for the trace analysis of HClO. In the presence of HClO, the sulfur atom on phenothiazine is rapidly oxidized to the sulfoxide, and a significant fluorescence enhancement (about 100-fold) was observed. Moreover, the advantages including fast response (<10 s), ultra-high sensitivity (limit of detection = 6 nM), strong specificity, and splendid light stability can all be achieved by PTZ-CHO. Benefitting from these advantages, this unique HClO-responding probe has been successfully applied to the detection of HClO in Hela cells, RAW 264.7 cells, and environmental water samples.

A NIR ratiometric fluorescence probe for rapid, sensitive detection and bioimaging of hypochlorous acid

Hypochlorous acid (HClO) is a condition where there is not enough oxygen in body tissues due to an imbalance between oxygen supply and consumption for cellular functions. In order to comprehend the biological functions of HClO within cells, the development of an effective and selective detection method is of great crucial. In this paper, a near-infrared ratiometric fluorescent probe (YQ-1) for detecting HClO was exploited based on a benzothiazole derivative. YQ-1′s fluorescence shifted from red to green with a large blue shift (165 nm) in the presence of HClO, and the solution's color changed from pink to yellow. YQ-1 quickly detected HClO (within 40 s) with a low detection limit (4.47 × 10−7 mol/L) and was not affected by other interferences. The mechanism of YQ-1′s response to HClO was confirmed by HRMS, 1H NMR and density functional theory (DFT) calculations. Moreover, due to its low toxicity, YQ-1 successfully utilized for fluorescence imaging for HClO both endogenous and exogenous in cells.

A novel strategy to construct activatable silver chalcogenide quantum dots nanoprobe for NIR-Ⅱ fluorescence imaging of hypochlorous acid in vivo

It is necessary to develop sensitive and selective probes for real-time in vivo monitoring of hypochlorous acid (HClO) which plays a significant role in physiological and pathological processes. The second near-infrared (NIR-Ⅱ) luminescent silver chalcogenide quantum dots (QDs) have shown great potential in developing activatable nanoprobe for HClO in terms of their outstanding imaging performance in the living organism. However, the limited strategy for the construction of activatable nanoprobes severely restricts their widespread applications. Herein, we proposed a novel strategy for developing an activatable silver chalcogenide QDs nanoprobe for NIR-Ⅱ fluorescence imaging of HClO in vivo. The nanoprobe was fabricated by mixing an Au-precursor solution with Ag2Te@Ag2S QDs to allow cation exchange and release Ag ions and then reducing the released Ag ions on the QDs surface to form an Ag shell for quenching of the emission of QDs. The Ag shell of QDs was oxidized and etched in the presence of HClO, resulting in the disappearance of their quenching effect on QDs and the activation of the QDs emission. The developed nanoprobe enabled highly sensitive and selective determination of HClO and imaging of HClO in arthritis and peritonitis. This study provides a novel strategy for the construction of activatable nanoprobe based on QDs and a promising tool for NIR-Ⅱ imaging of HClO in vivo.

A cyanine carbazole oxime fluorescent probe selectively detects hypochlorite in Hi5 cells and C. elegans

Quantitative detection and visualization of hypochlorous acid (HClO) in biological samples has emerged as a hot topic in biochemical research because of the important role of this biomolecule in live organisms. In this contribution, a novel hemicyanine-based fluorescence probe, CVDI (1-ethyl-2-((E)-2-(9-ethyl-6-((E)-(hydroxyimino)methyl)-9H-carbazol-3-yl)vinyl)-3,3-dimethyl-3H-indol-1-ium), was designed and synthesized for HClO detection in aqueous solutions and in biological systems. In the presence of HClO, significant changes in absorption and fluorescence spectra were observed and the fluorescence response has increased by a factor of nine, which allow for the quantitative detection of HClO in PBS buffer. CVDI has excellent fluorescence properties: fast response time (20 s) and remarkable stability at wide pH range (7.0–10.0). The detection limit for HClO was determined to be 1.304 μM. Imaging of exogenous HClO in live Hi5 cells and C. elegans was then successfully performed using CVDI. We anticipate that CVDI could be employed for the diagnosis of pathological inflammation in clinic in near future.

Kinetic and mechanistic investigations of dioxygen reduction by a molecular Cu(II) catalyst bearing a pentadentate amidate ligand.

A pentadentate Cu(II) complex, [CuII(dpaq)](ClO4) (1), featuring a redox active ligand, H-dpaq (H-dpaq = 2-[bis(pyridine-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate), catalyses four-electron reduction of dioxygen by decamethylferrocene (Fc*) in the presence of trifluoroacetic acid (CF3COOH) in acetone at 298 K. No catalytic oxygen reduction was observed in the presence of stronger Brønsted acids than CF3COOH, such as perchloric acid (HClO4) or trifluoromethanesulphonic acid (HOTf). In contrast, facile catalytic reduction of O2 occurs by Fc* with 1 and HClO4 or HOTf in dimethylformamide (DMF). The use of CF3COOH as the proton source in DMF results in the suppression of O2 reduction under otherwise identical reaction conditions. While the O2 reduction reactions in DMF are linearly dependent on the pKa of Brønsted acids, the acid dependence on catalytic O2-reduction reactivity by 1 in acetone showed complete reversal. Cyclic voltammetry studies using p-chloranil as the probe substrates in the presence of acids in the solvents reveal that the strengths of the protonic acids increase significantly in acetone compared to that in DMF. The amidate-N in [CuII(dpaq)](ClO4) (1) undergoes protonation in the presence of HClO4 or HOTf in DMF to form [CuII(H-dpaq)]2+ (1-H+), but not in the presence of CF3COOH. Enhanced acid strength of CF3COOH in acetone, however, effectively protonates 1 and triggers O2 reduction. Protonation of 1 with HClO4 or HOTf in acetone results in the change of its coordination environment, and this protonated species does not trigger O2 reduction. Detailed kinetic studies indicate that 1-H+ undergoes reduction by two-electrons and the reduced species binds O2 to form a Cu(II)-superoxo intermediate. This is followed by a rate-determining proton-coupled electron-transfer (PCET) reduction to generate the Cu(II)-hydroperoxo intermediate. While catalytic O2 reduction in acetone occurs predominantly via a 4e-/4H+ pathway, product selectivity (H2O vs. H2O2) in DMF depends upon the concentration of the reductant (Fc*). While dioxygen reduction to H2O2 is favoured at low [Fc*], mechanistic studies suggest that O2 reduction with high [Fc*] proceeds via a [2e- + 2e-] mechanism, where the released H2O2 during catalysis is further reduced to water.

Energetic [1,2,5]oxadiazolo [2,3-a]pyrimidin-8-ium Perchlorates: Synthesis and Characterization

A convenient method to access the above perchlorates has been developed, based on the cyclocondensation of 3-aminofurazans with 1,3-diketones in the presence of HClO4. All compounds were fully characterized by multinuclear NMR spectroscopy and X-ray crystal structure determinations. Initial safety testing (impact and friction sensitivity) and thermal stability measurements (DSC/DTA) were also carried out. Energetic performance was calculated by using the PILEM code based on calculated enthalpies of formation and experimental densities at r.t. These salts exhibit excellent burn rates and combustion behavior and are promising ingredients for energetic materials.

Theoretical study on a series of naphthalimide-contained two-photon fluorescent hypochlorite probe targeting endoplasmic reticulum: response mechanism and receptor effect.

The development of detecting hypochlorous acid (HClO) in living endoplasmic reticulum has attracted much attention in the fields of biology, medicine, and pharmacy. In the present work, the one-photon absorption (OPA), one-photon emission (OPE), and two-photon absorption (TPA) properties of a series newly synthesized chemosensors with naphthalimide as the fluorophore were systematically investigated using time-dependent density functional theory in combination with response theory. Special emphasis is placed on evolution of the probes' optical properties in the presence of HClO. These compounds show drastic changes in their photoabsorption and photoemission properties when they react with HClO, indicating them to be excellent candidates as fluorescent chemosensors. To further understand the mechanisms of the two probes, we have employed the hole and electron analysis to investigate the charge transfer process for the photoemission of the molecules. The receptor effect is found to play a dominant role in the sensing performance of these probes. Specifically, two-photon absorption properties of the molecules are calculated. We have found that all probes show significant two-photon responses in the near-infrared light region. And the maximum two-photon absorption cross section of probe 2 is greatly enhanced with the presence of HClO, indicating that probe 2 can act as a potential two-photon excited fluorescent HClO probe. The theoretical investigations would be helpful to build the structure-property relationships for the naphthalimide-contained probes, providing information on the design of efficient two-photon fluorescent sensors that can be used for biological imaging of HClO in endoplasmic reticulum.

THE INFLUENCE OF ACID PROTEIN PRECIPITANTS ON THE SPECIFICITY OF THE REACTION OF NINHYDRIN WITH AMINO ACIDS

Aim. The purpose of the work was to determine the effect of trichloroacetic (TCA) and perchloric (HClO4) acids on the result of ninhydrin reaction with various amino acids. Methods. A standard method of amino acid detection using a ninhydrin reagent was applied. Optical spectra and density of reaction products were determined spectrophotometrically. Results and conclusions. As a result, it was found that the studied acids change the spectral characteristics of the products of the ninhydrin reaction with amino acids. TCA significantly reduced the optical density of chromophores, and HClO4 also led to a significant shift of the spectra of the reaction products into the short-wavelength region. An exception was the reaction with proline, as a result of which a well-defined maximum appeared in the product spectrum: λ= 620 nm in the presence of TCA and λ=515 nm with HClO4. At the same time, in the presence of HClO4, the reaction became highly specific for proline. Conditions. The ninhydrin reaction with proline upon addition of HClO4 were analyzed in detail. As a result, a new method of highly specific determination of proline in the presence of other amino acids was proposed.

An acid-enhanced OFF-ON fluorescent probe for the detection of hypochlorous acid in rheumatoid arthritis

Excessive production of hypochlorite acid (HClO) and lactic acid are general hallmarks in the microenvironment of rheumatoid arthritis (RA). Here, we, for the first time, report an acid-enhanced “OFF-ON” fluorescent probe PPS for the detection of HClO in vivo. The probe PPS showed good water solubility, large Stokes shift (143 nm), and fast response toward HClO within 100 s. In the presence of HClO, the sulfur atom in the core of phenothiazine would be oxidized into sulfoxide, triggering intense fluorescence at 580 nm, whose fluorescence intensity could be further enhanced under acidic conditions. Moreover, the exogenous and endogenous HClO in living cells could be sensitively and selectively detected by PPS with a low LOD of 24 nM. Notably, PPS was able to rapidly visualize endogenous HClO generation in a RA mouse model, exhibiting a 2.3-fold higher fluorescence intensity than it in normal joint and 4.1-fold enhanced fluorescence intensity at acidic pH.

A new HClO-activated “turn-off” mitochondria-targetable NIR fluorescent probe for imaging of osteoarthritis in vivo

Hypochlorous acid (HClO) as a biomarker of inflammation has been implicated in redox signaling and combating microbial infection. Therefore, it is of great significance to develop an efficient method for detection and analysis of HClO in osteoarthritis. Herein, a new“turn-off” mitochondria-targetable NIR fluorescent probe, NIR-ClO, was reported for specific analysis and imaging of osteoarthritis response-related HOCl levels in vitro and in vivo. In the presence of HClO, due to the specific HOCl-triggered C = C bond cleavage reaction, NIR-ClO obtained a high sensitive and selective fluorescence “On-Off” response toward HClO with a good limit of detection(LOD) as low as 28.3 nM, and showed a fast response time (<60 s) , which allow it to be used for detection of HClO under a simulated physiological condition. In addition, NIR-ClO was successfully used to imaging of HClO in living RAW264.7 cells and osteoarthritis model rat. The results suggest that NIR-ClO is a robust tool for future studies on diagnosis osteoarthritis.

Visualization of biothiols and HClO in cancer therapy via a multi-responsive fluorescent probe

Cancer is among the most important diseases threatening human life and health, and drug chemotherapy is an effective method which can be used to treat cancer. Last several years, although a growing anti-tumor drugs have been discovered, there still lacks direct visual evidence for reactive sulfur/oxygen species (RS/OS) during cancer therapy. Herein, a novel fluorescence probe RSS-HClO was reported for detecting Cys/Hcy, GSH and HClO at three channels with coumarin-hemicyanine moiety and NBD chloride (NBD-Cl) moiety as fluorophore and recognition group. RSS-HClO shows almost no fluorescence due to the hydroxyl group is protected by NBD. The fluorescence was significantly increased in green and red channels after the reaction with Cys/Hcy. For GSH, the fluorescence was increased in red channel while the green channel fluorescence presented no noticeable change. Conversely, the fluorescence increased only in blue channel in the presence of HClO. Additionally, RSS-HClO exhibits low detection limit with short response time toward three thiols and HClO. The multi-responsive fluorescent probe RSS-HClO allows the distinction of three biothiols and HClO in cells and zebrafish. We hope that RSS-HClO can be invoked as a potential and effective tool for investigating the pharmacological processes during cancer therapy.

Facile Synthesis, Spectral and Electrochemical Properties and Catalytic Efficiencies of β-Octabromo Vanadyl Porphyrin

Selective oxidation of olefins to epoxy compounds has always been an interesting area of research for chemists owing to their great importance in the production of highly valued commodity chemicals such as polyurethanes, unsaturated resins, glycols, surfactants, and other products. Further, oxidative bromination of thymol and other phenolic derivatives has industrial importance. Iron and manganese porphyrins have been widely utilized as effective homogeneous catalysts for such oxygenation reactions in the last few decades. The major drawbacks of homogeneous MTPP-based catalysts are the macrocyclic ring which is liable to oxidative self-destruction, aggregation of metalloporphyrins through π–π interactions, lower turnover frequency (TOF) and poor product selectivity. Notably, vanadyl porphyrins have gained significant interest as useful molecules with applications in the fields of therapeutics, catalysis and 3D supramolecular assemblies. Herein, we synthesized vanadyl complex of β-octabromo-meso-tetraphenylporphyrin (VOTPPBr8) by self-catalytic reaction of VOTPP in excellent yield ar room temperature under mild bromination conditions using KBr/H2O2 in presence of HClO4. Further, VOTPPBr8 was utilized as an efficient catalyst for the epoxidation and oxidative bromination reactions. In this presentation, we will present facile synthesis, spectral and electrochemical properties and catalytic efficiencies of VOTPP and VOTPPBr8 in detail.

A Sensitive and Selective Fluorescent Probe for Real-Time Detection and Imaging of Hypochlorous Acid in Living Cells.

Hypochlorous acid (HClO), a reactive oxygen species, plays an essential role in the processes of physiology and pathology via reacting with most biological molecules. The abnormal level of HClO may cause inflammation, especially arthritis. To further understand its key role in inflammation, in situ detection of HClO is necessary. Herein, a water-soluble small molecule fluorescent probe (HDI-HClO) is employed to monitor and identify trace amounts of HClO in the biological system. In the presence of HClO, the probe releases a hydroxyl group emitting strong fluorescence because of the restoration of the intramolecular charge transfer process. Furthermore, this probe displays a 150-fold fluorescence enhancement accompanied by a large Stokes shift and a lower detection limit (8.3 nM). Moreover, the probe can make a rapid response to HClO within 8 s, which provides the possibility of real-time monitoring of intracellular HClO. Based on the advantages of rapid dynamics, good water solubility, and excellent biocompatibility, this probe could effectively monitor the fluctuations of exogenous and endogenous HClO in living cells. The fluorescence imaging of HDI-HClO indicated that it is an excellent potential approach for comprehending the relationship between inflammation and HClO.

Chromene, Quinoline Hybrids as Potential Anti-Cancer Agents: A Novel and Distinct Approach for the Synthesis of Quinoline Derivatives

A series of novel quinoline derivatives (6-phenyl-6H-chromeno[4,3-b]quinoline) have been prepared by using 4-chloro-2-phenyl-2H-chromene-3-carbaldehyde and various substituted isocyanides as starting materials in the presence of HClO&lt;sub&gt;4&lt;/sub&gt;-SiO&lt;sub&gt;2&lt;/sub&gt; and Methanol. We screened eighteen compounds of this novel series (6a-r) in six different cancer cell lines (A549 (lung cancer cells), DU145 (prostate cancer cells), PC3 (prostate cancer cells), MCF7 (lung cancer cells), HT 29, HCT 116 (colon cancer cells). Most of the compounds showed anti-cancer activity and compound 6b showed good cytotoxicity IC50 = 2.61±0.34 μM against colon cancer on HT29 cell line among all. The key property of cell migration was observed while treatment cells with 6b. Apoptosis in HT29 cells confirmed by annexin V staining, acridine orange/ethidium bromide (AO/EB), DAPI, induced by 6b. This method is operationally simple and works with a diverse range of substrates. These results indicate the anticancer potential of these series and warrants future investigations for further anticancer drug development.

Influence of Reduced Graphene Oxide on the Electropolymerization of 5-amino-1-naphthol and the Interaction of 1,4-phenylene Diisothiocyanate with the Poly(5-amino-1-naphtol)/Reduced Graphene Oxide Composite.

A new composite base on reduced graphene oxide (RGO) and poly(5-amino-1-naphthol) (P5A1N) was synthesized by the electrochemical polymerization of 5-amino-1-naphthol (5A1N) in the presence of HClO4 and H4SiW12O40 onto the surface of Au electrode covered with the RGO sheets. The linear dependence of the current densities of the anodic and cathodic peaks with the scan rate of the potential range (0; 0.8) V vs. SCE, reported during electropolymerization of 5A1N, indicates an electron transfer that is controlled by diffusion. A covalent functionalization of the RGO sheets with P5A1N is argued by: (i) the simultaneous disappearance of the IR band at 1584 cm−1 and the appearance of the new IR bands at 812, 976 and 3744 cm−1, and (ii) the appearance of two Raman lines at 738 and 1428 cm−1. An application of the RGO sheets covalently functionalized with P5A1N is demonstrated to support 1,4-phenylene diisothiocyanate (PDITC), a compound used as a cross-linking agent for various biological applications. The chemical adsorption of PDITC onto the RGO sheets covalently functionalized with P5A1N, which involves the appearance of new functional groups of the type thiourea, was proven by Raman scattering and IR spectroscopy.

Facile and Highly Selective Ratiometric Fluorescence Probe Based on Benzo[5]helicene for the Detection of Hypochlorous Acid

In physiological processes, hypochlorous acid can regulate in vitro signaling molecules as one kind of reactive oxygen species (ROS). Serious diseases, such as cardiovascular disorders, neurodegenerative diseases, Alzheimer’s disease, and cancers are usually concerned with the abnormal levels of hypochlorous acid in human bodies. Herein, we report a new probe DPH-BP for HClO, which consists of a benzo[5]helicene-pyridine fluorophore and benzyl-benzeneboronic acid pinacol ester as HClO reaction sites. The structural motifs combined with chromogenic media and fluorescence become a single-molecule sensor response in aqueous solutions. In the presence of HClO, this probe shows a remarkable blue shift of fluorescence from 536 to 452 nm in an aqueous solution and obvious fluorescence color change from yellow to blue. In the same conditions, almost no response can be recorded with the other common ROS/RNS, such as H2O2, TBHP, •OH, t-BuO•, ONOO–, and O2•–. As we have designed, the oxidation of phenylboronic ester by HClO induces the cleavage of the benzyl in DPH-BP, which has been proven by 1H NMR spectra and density functional theory calculations. To the best of our knowledge, this is the first report of the analysis of HClO using the oxidation of benzyl-benzeneboronic acid pinacol ester.

Vanadium(V) and Molybdenum(VI) Complexes Containing ONO Tridentate Schiff Bases and Their Application as Catalysts for Oxidative Bromination of Phenols

AbstractCondensation of 2,4‐dihydroxyacetophenone with isonicotinoyl hydrazide and nicotinoyl hydrazide in an equimolar ratio in methanol results in the formation of two stable ONO donor ligands, H2dhap‐inh (I) and H2dhap‐nah (II), respectively. These ligands react with [VIVO(acac)2] (Hacac=acetylacetone) in 1:1 molar ratio to give the corresponding neutral dioxidovanadium(V) complexes, [VVO2(Hdhap‐inh)] (1) and [VVO2(Hdhap‐nah)] (2), after overnight aerial oxidation in the presence of K2CO3. In the absence of K2CO3, they result in (μ‐O){bisoxidovanadium(V)} complexes, [{VVO(dhap‐inh)}2(μ‐O)] (3) and [{VVO(dhap‐nah)}2(μ‐O)] (4). Treatment of neutral dioxidovanadium(V) complexes,1and2, with H2O2yields oxidoperoxidovanadium(V) complexes K[VVO(O2)(dhap‐inh)(H2O)] (5) and K[VVO(O2)(dhap‐nah)(H2O)] (6). The ligands also react with [MoVIO2(acac)2] in 1:1 molar ratio to form [MoVIO2(dhap‐inh)]n(7) and [MoVIO2(dhap‐nah)]n(8). The reaction of oxidoperoxidomolybdenum(VI) species, generated in situ by the reaction of MoO3with H2O2with ligandsIandII, gives the oxidoperoxidomolybdenum(VI) complexes, [MoVIO(O2)(dhap‐inh)(MeOH)] (9) and [MoVIO(O2)(dhap‐nah)(MeOH)] (10), respectively. All synthesized complexes are characterized by elemental analysis, thermogravimetric, electrochemical, spectroscopic (IR, UV–Vis,1H,13C and51V NMR) and single crystal X‐ray diffraction (for1,2and8). Complexes are explored as catalysts for the oxidative bromination of phenol, a model oxidative halogenation reaction, in the presence of HClO4and KBr, using 30% H2O2as oxidant. Under optimized reaction conditions, the product selectivity follows the order: 4‐bromophenol&gt;2‐bromophenol, both for molybdenum and vanadium complexes. Products characterized by GC analysis showed very good conversion of phenol.