Manganese Porphyrin Research Articles

Catalytic performance of modified multi-walled carbon nanotubes with manganese(III) porphyrin in aerobic olefin oxidation

In the present research, the catalytic activity of an immobilized manganese porphyrin onto the surface of multi-walled carbon nanotubes was investigated in the oxidation of alkenes with molecular oxygen as a “green” oxidant under mild conditions. The prepared nanohybrid was fully characterized by X-ray diffraction (XRD), UV-Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetry and differential scanning calorimetry (TGA/DSC), Fourier transform infrared (FTIR) and atomic absorption spectroscopy (AAS). Excellent conversion and high selectivity was observed for the oxidation of a variety of olefins in the presence of [Mn(THPP)OAc@MWCNT] at room temperature in 2 hours reaction time. The solid catalyst was reused at least 5 times without any loss of activity or selectivity providing scalability of this catalytic system. Moreover, high turnover number (45500) was achieved for the aerobic oxidation of styrene, which proved the longevity and stability of the supported catalyst.

Antioxidant cytochrome c-like activity of para-Mn(III)TMPyP

Manganese porphyrins are well-known protectors against the deleterious effects of pro-oxidant species such as superoxide ions and hydrogen peroxide. The present study investigated the antioxidant cytochrome c-like activities of Mn(III)TMPyP [meso-tetrakis (4-N-methyl pyridinium) porphyrin] against superoxide ion and hydrogen peroxide that remained unexplored for this porphyrin. The association of TMPyP with a model of the inner mitochondrial membrane, cardiolipin (CL)-containing liposomes, shifted +30 mV vs. NHE (normal hydrogen electrode) redox potential of the Mn(II)/Mn(III) redox couple. In CL-containing liposomes, Mn(III)TMPyP was reduced by superoxide ions and recycled by Fe(III)cytochrome c to the oxidized form. Similarly, isolated rat liver mitoplasts added to a sample of Mn(II)TMPyP promoted immediate porphyrin reoxidation by electron transfer to the respiratory chain. These results show that Mn(III)TMPyP can act as an additional pool of Fe(III)cytochrome c capable of transferring electrons that escape from the IV complex back into the respiratory chain. Unlike Fe(II)cytochrome c, Mn(II)TMPyP was not efficient for hydrogen peroxide clearance. Therefore, by reducing cytochrome c, Mn(II)TMPyP can indirectly contribute to hydrogen peroxide elimination.

Manganese(III) porphyrin oligomers as high-relaxivity MRI contrast agents

Manganese(III) porphyrins (MnIIIPs) as MRI contrast agents (CAs) have drawn particular attention due to their high longitudinal relaxivity (r1) and unique biodistribution. In this work, two MnIIIP-based oligomers, MnPD and MnPT, were designed to further improve the relaxivity with ease of synthesis. The two compounds were fully characterized and their nuclear magnetic relaxation dispersion (NMRD) profiles were acquired with a fast field cycling NMR relaxometer. Both of the compounds exhibited extended high molar r1 at high fields, higher than that of Gd-DTPA, the first clinical gadolinium(III)-based MRI CA. The r1 value of per manganese atom increased with the increasing number of MnIIIP building blocks, suggesting rotational correlation time (τR) played dominant role in the r1 dispersion. The toxicity of the two MnIIIPs and the imaging effectiveness were estimated in vitro and in vivo. With good biocompatibility, significant contrast enhancement, and complete excretion in 24 h, MnPD and MnPT are both promising for high field clinical applications. The applied strategy also potentially provided a facile approach for creation of more MnIIIP oligomer as efficient T1 MRI CAs.

Enantioselective Synthesis of Diaryl Sulfoxides Enabled by Molecular Recognition.

The enantioselective sulfoxidation of diaryl-type sulfides was accomplished using a chiral manganese porphyrin complex equipped with a remote molecular recognition site. Despite the marginal size difference between the two substituents at the prostereogenic sulfur center, hydrogen bonding enabled the formation of chiral sulfoxides with exquisite enantioselectivities (16 examples, up to 99% ee). Aside from the precise orientation of a distinct substrate, the quinolone lactam offers an excellent entry point for further derivatization.

The oxidative reactivity of three manganese(III) porphyrin complexes with hydrogen peroxide and nitrite toward catalytic nitration of protein tyrosine.

Understanding the toxicological properties of MnIII-porphyrins (MnTPPS, MnTMPyP, or MnTBAP) can provide important biochemical rationales in developing them as the therapeutic drugs against protein tyrosine nitration-induced inflammation diseases. Here, we present a comprehensive understanding of the pH-dependent redox behaviors of these MnIII-porphyrins and their structural effects on catalyzing bovine serum albumin (BSA) nitration in the presence of H2O2 and NO2-. It was found that both MnTPPS and MnTBAP stand out in catalyzing BSA nitration at physiologically close condition (pH 8), yet they are less effective at pH 6 and 10. MnTMPyP was shown to have no ability to catalyze BSA nitration under all tested pHs (pH 6, 8, and 10). The kinetics and active intermediate determination through electrochemistry method revealed that both the pH-dependent redox behavior of the central metal cation and the antioxidant capability of porphin derivative contribute to the catalytic activities of three MnIII-porphyrins in BSA nitration in the presence of H2O2/NO2-. These comprehensive studies on the oxidative reactivity of MnIII-porphyrins toward BSA nitration may provide new clues for searching the manganese-based therapeutic drugs against the inflammation-related diseases.

Modification of magnetocaloric properties upon a change in the spin state of iron(III) in tetrapyrrole paramagnets

Porphyrin complexes of 3d-metals with an open electronic shell are ranked as molecular materials with both electronic functionality and paramagnetic behavior due to exhibiting a positive magnetocaloric effect (MCE) at the temperature close to the room. We have determined MCE, heat, and an enthalpy/entropy change during magnetization of chloride ligated pentacoordinated iron(III) 5,10,15,20-tetraphenylporphin, (Cl)FeTPP and dimethylformamide ligated sixcoordinated iron(III) mesoporphyrin IX, [(DMF)2FeMP]+Cl- at 278–338 K in magnetic fields from 0 to 1.0 T by the direct microcalorimetric method. The specific heat capacity in solid (Cl)FeTPP/[(DMF)2FeMP]+Cl- was directly determined depending on the temperature in zero magnetic fields using DSC. To improve understanding of the correlation between magnetic properties of the iron(III) complexes and its spin state, we have compared the magnetic behavior of paramagnets studied with those for manganese(III) porphyrins. Both the iron(III) spin state and the exchange (ferromagnetic or antiferromagnetic depending on functional substitution in a complex) between a paramagnetic ligand and the central ion are reflected in the magnetocaloric behavior of iron(III) porphyrins studied.

Post-Modification of Mesoporous Silica with Different Nitrogenous Bases for Immobilization of Manganese Porphyrin: Synthesis, Characterization and Catalytic Activity

Post-Modification of Mesoporous Silica with Different Nitrogenous Bases for Immobilization of Manganese Porphyrin: Synthesis, Characterization and Catalytic Activity

An ultra-sensitive gas sensor based on a two-dimensional manganese porphyrin monolayer.

The development of highly sensitive, low-power consuming, stable and recyclable gas sensing devices at room temperature has become an important solution for environmental safety detection. Utilizing a two-dimensional metalloporphyrin monolayer for gas sensing is appealing due to its large specific surface area and high surface activity. A two-dimensional manganese porphyrin monolayer (2DMnPr) is selected from 2D metalloporphyrins with 3d metal centers due to its semi-metallicity to explore its gas sensing properties. Using first-principles calculations, we systematically investigate the electronic structures and adsorption characteristics of gas molecules with toxicity and greenhouse effect on the surface of 2DMnPr, including H2S, CO, CO2, SO2, NO and NO2. The strength of the interaction and charge transfer between the 2DMnPr surface and the adsorbed molecules have a direct effect on the electronic properties and the sensing properties of the adsorbent surface. The sensing performance of the 2DMnPr adsorbent is evaluated via two observable parameters: work function and electrical conductivity. The work functions of 2DMnPr after the adsorption of CO, SO2, NO and NO2 gas molecules increase by different degrees depending on the charge transfer, and those of the H2S and CO2 cases decrease. In our simulation, adsorption of CO, SO2, NO and NO2 gas molecules affects the electronic properties of 2DMnPr markedly, and current-voltage characteristics within a low bias range uncover the superior sensitivity of the conductivity of the 2DMnPr monolayer to these molecules. Besides, the sensing performance is demonstrated to be stable under strain and at room temperature. The desorption time of a gas is positively related to its adsorption energy. The recovery time of CO is predicted to be short enough to realize sustainable detection at room temperature, and the SO2, NO and NO2 gases can also be desorbed at higher temperatures. These results demonstrate that 2DMnPr enables the sensitive detection of these gases and predict the potential application of 2DMnPr as an ultra-sensitive, low-power, stable and recyclable gas sensor at room temperature.

Water-soluble manganese porphyrins as good catalysts for cipro- and levofloxacin degradation: Solvent effect, degradation products and DFT insights

Synthetic manganese porphyrins (MnPs), in the presence of oxidants, were employed for the degradation of fluoroquinolone antibiotics. Ciprofloxacin (CIP) and levofloxacin (LEV) degradation by iodosylbenzene, iodobenzene diacetate, H2O2 and meta-chloroperbenzoic acid using water-soluble MnP catalysts yielded thirteen and nine products, respectively, seven of which have been proposed for the first time. The MnP catalysts have demonstrated the ability to degrade these antibiotics to a high degree (up to 100% degradation). The structures of the degradation products were proposed based on mass spectrometry analysis, and density functional theory calculations could confirm how the substituent moieties attached to the basic chemical structure of the fluoroquinolones influence the degradation reactions. CIP has been shown to be a more reactive substrate towards the porphyrinic catalysts tested because of its three-membered ring. However, the catalysts could almost completely degrade LEV, highlighting the ability of these porphyrins to act as catalysts to degrade environmental pollutants.

Manganese Porphyrin and Radiotherapy Improves Local Tumor Response and Overall Survival in Orthotopic Murine Mammary Carcinoma Models.

Novel synthetic compounds, known as manganese porphyrins (MnPs), have been designed to shift the redox status of both normal cells and cancer cells. When MnPs are coupled with cancer therapies, such as radiation, they have been shown to sensitize tumor cells to treatment and protect normal tissues from damage through the modulation of the redox status of various tissue types. Until now, our preclinical studies have focused on local effects of MnPs and radiation; however, we recognize that successful outcomes for cancer patients involve control of tumor cells throughout the body. In this study, using murine orthotopic mammary tumor models, we investigated how MnPs and radiation influence the development of distant metastasis. We hypothesized that the combination of MnP (MnP/RT), such as MnTnBuOE-2-PyP5+ and radiation treatment (RT) would increase local tumor control via a shift in the intratumoral redox environment, leading to subsequent downregulation of HIF-1 in the primary tumor. Secondarily, we hypothesized that these primary tumor treatment effects would result in a reduction in pulmonary metastatic burden. Balb/c mice with orthotopic 4T1 mammary carcinomas were treated with saline, MnP, RT or MnP/RT. We found MnP/RT did extend local tumor growth delay and overall survival compared to controls and was associated with increased intratumoral oxidative stress. However, the primary tumor growth delay observed with MnP/RT was not associated with a reduced pulmonary metastatic burden. Future directions to investigate the effects of MnP/RT on the development of distant metastasis may include modifications to the radiation dose, the experimental timeline or using a murine mammary carcinoma cell line with a less aggressive metastatic behavior. Clinical trials are underway to investigate the clinical utility of MnTnBuOE-2-PyP5+ for patients undergoing radiotherapy for various tumor types. The promising preclinical data from this study, as well as others, provides support that MnP/RT has the potential to improve local tumor control for these patients.

Nitric Oxide Dioxygenation by O2 Adducts of Manganese Porphyrins.

We describe here nitric oxide dioxygenation (NOD) by the dioxygen manganese porphyrin adducts Mn(Por)(η2-O2) (Por2- = the meso-tetra-phenyl or meso-tetra-p-tolylporphyrinato dianions, TPP2- and TTP2-). The Mn(Por)(η2-O2) was assembled by adding O2 to sublimed layers of MnII(Por). When NO was introduced and the temperature was slowly raised from 80 to 120 K, new IR bands with correlated intensities grew concomitant with depletion of the υ(O2) band. Isotope labeling experiments with 18O2, 15NO, and N18O combined with DFT calculations provide the basis for identifying the initial intermediates as the six-coordinate peroxynitrito complexes (ON)Mn(Por)(η1-OONO). Further warming to room temperature led to formation of the nitrato complexes Mn(Por)(η1-ONO2), thereby demonstrating the ability of these metal centers to promote NOD. However, comparable quantities of the nitrito complexes Mn(Por)(η1-ONO) are also formed. In contrast, when the analogous reactions were initiated with the weak σ-donor ligand tetrahydrofuran or dimethyl sulfide present in the layers, formation of Mn(Por)(η1-ONO2) is strongly favored (∼90%). The latter are formed via a 6-coordinate intermediate (L)Mn(Por)(η1-ONO2) (L = THF or DMS) that loses L upon warming. These reaction patterns are compared to those observed previously with analogous iron and cobalt porphyrin complexes.

Signal-off photoelectrochemical biosensing platform based on hybridization chain-doped manganese porphyrin quenching on CdSe signal coupling with cyclic amplification for thrombin detection

A novel signal-off photoelectrochemical (PEC) biosensing platform based on hybridization chain-doped manganese porphyrin quenching on PEC signal of CdSe quantum dots (QDs) coupling with cyclic amplification was developed for thrombin detection. Target thrombin firstly induced DNA enzyme-aided cyclic amplification reaction and produced abundant DNA I. Then DNA I hybridized with capture DNA on the TiO 2 /CdSe QDs modified electrode to form DNA bridge, which triggered a linear chain hybridization reaction with S4 and S5. Numerous manganese porphyrin (MnPP) were doped in the long double-stranded DNA chain, which hindered electron transfer and resulted in obvious decrease of QDs PEC signal, achieving a sensitive detection of thrombin. This PEC biosensor exhibits excellent performance with a wide linear range from 1.0 f. to 100.0 nM and detection limit of 0.331 fM, and the recovery value ranged from 95.5% to 103.5%. The results suggest that this PEC biosensor has high sensitivity and precision, showing great application prospect in microbiological analysis of biomolecules and clinical medicine. • A novel signal-off PEC biosensor based on DNA linear chain-doped MnPP quenching to QDs was reported. • CdSe QDs and TiO 2 complex displayed strong PEC signal. • A large amount of manganese porphyrin doped in linear DNA chain greatly amplified PEC signal change. • DNA S1 and S2 specifically bind to thrombin to form the pliers structure with high selectivity.

Protective Role of Manganese Porphyrin Against Radiation-induced Damage in a Diabetic Environment

Protective Role of Manganese Porphyrin Against Radiation-induced Damage in a Diabetic Environment

Temperature-sensitive effect of topological polymers: Application of polymer-supported manganese porphyrins in catalytic oxidation of low concentration ferrous iron

The temperature-sensitive branched heterogeneous catalyst was designed and fully characterized. The synthesis involves the preparation of the intermediate that protoporphyrins (PP) were immobilized onto polyvinyl alcohol (PVA), which was used to produce polymer support with branched chains poly(N-isopropylacrylamide) (PP-PVA-PNIPAm) via photo-induced electron/energy transfer reversible addition-fragmentation chain transfer polymerization. And then PP-PVA-PNIPAm was metalated with manganese to form the temperature-sensitive branched heterogeneous Mn(III)(PP)Cl-PVA-PNIPAm. To test temperature-sensitive effect of Mn(III)(PP)Cl-PVA-PNIPAm in catalytic process, it was used for the catalytic oxidation of low concentration Fe2+, which plays an important role in sustaining equilibrium between Fe2+ and Fe3+ in life. The results showed that the catalytic efficiency of Mn(III)(PP)Cl-PVA-PNIPAm was higher than the unsupported manganese porphyrins and exhibited a downward trend after the first rise with the increase of reaction temperature. High temperature resulted in the shrink of temperature-sensitive branched chains of Mn(III)(PP)Cl-PVA-PNIPAm and increased mass transfer resistance in the reaction process. According to the density functional theory calculation, the interaction energy between oxidant H2O2 and shrunken Mn(III)(PP)Cl-PVA-PNIPAm is weaker than that of H2O2 with unshrinking Mn(III)(PP)Cl-PVA-PNIPAm. Moreover, the temperature-sensitive effect of Mn(III)(PP)Cl-PVA-PNIPAm is dependent on the graft ratio and the length of branched chains. The topological polymers with temperature-sensitive branched chains are potential support for catalysts to suppress the runaway phenomenon in catalyticexothermalreactions.

Solvent and Anion Effects on the Electrochemistry of Manganese Dipyrrin-Bisphenols.

A series of "N2O2-type" manganese dipyrrin-bisphenols (DPP), formulated as (Ar)DPPMn, where Ar = pentafluorophenyl (F5Ph), phenyl (Ph), or mesityl (Mes), were electrochemically and spectroscopically characterized in nonaqueous media with and without added anions in the form of tetrabutylammonium salts (TBAX where X = ClO4-, PF6-, BF4-, F-, Cl-, OH-, or CN-). Two major one-electron reductions are observed under most solution conditions, the first of which is assigned as a MnIII/II process and the second as electron addition to the π-ring system as confirmed by spectroelectrochemistry. Each MnIII complex also exhibits one or two one-electron oxidations, the exact number depending upon the positive potential limit of the electrochemical solvent. The two oxidations are separated by 580-590 mV in CH3CN containing 0.1 M TBAPF6 and are assigned as π-ring-centered electron transfers to stepwise form a (Ar)DPPMnIII π-cation radical and dication under these solution conditions. Comparisons are made between redox properties of (Ar)DPPMn and manganese(III) porphyrins, corroles, and corrolazines each of which contains an innocent trianionic complexing ligand. The redox behavior and spectroscopic properties of [(Ar)DPPMn]n where n = 0, -1, or +1 are also compared to that of other structurally related [(Ar)DPPM]n complexes under similar solution conditions where M = CoII, CuII, BIII, or AuIII.

Manganese complex catalyst for valencene oxidation: The first use of metalloporphyrins for the selective production of nootkatone

This work describes the oxidation of valencene, a sesquiterpene easily obtained from citrus fruits, and responsible for the fresh odor of oranges. The reactions were catalyzed by manganese porphyrins derived from 5,10,15,20-tetrakis(3,5-dimethoxyphenyl)porphyrin (H2T3,5DMPP): [MnIII(T3,5DMPP)Cl] (MnP1) and [MnIII(Br12T3,5DMPP)Cl] (MnP2), using iodosylbenzene (PhIO), iodobenzene diacetate [PhI(OAc)2], and molecular oxygen as oxidants. The systems MnP1/O2/acetonitrile and MnP1/O2/diethyl carbonate led to higher yields of valencene oxidation products (44% and 48%, respectively) as compared with MnP2 (9% and 7%, respectively), with nootkatone being the major product. The addition of a small amount of imidazole (molar MnP1: imidazole ratio of 1:5) to the MnP1/O2/diethyl carbonate led to superior yields (64%) as compared with systems without the additive. A mechanism for the formation of the two products obtained was also proposed.

Full use of factors promoting catalytic performance of chitosan supported manganese porphyrin

In order to make full use of the impact of internal and external factors on the performance of title catalyst for ethyl benzene oxidation, the key internal influencing factors on the catalytic performance were modulated by coordinating and grafting manganese porphyrin to mesoporous and macroporous chitosan, and the important external factors (i.e. oxidation reaction conditions) were optimized using Response Surface Methodology. Under the Response Surface Methodology optimized oxidation reaction conditions (176.56 °C, 0.59 MPa, and 0.25 mg amount of manganese porphyrin), the catalyst could be used at least five times. The ethyl benzene conversion, catalyst turnover numbers, and yields reached up to 51.2%, 4.37 × 106 and 36.4% in average, respectively. Compared with the other optimized oxidation reaction conditions, the corresponding values increased 17%, 26% and 53%. Relative to the manganese porphyrin, the catalytic performance and efficiency of the immobilized catalyst had notably increased.

Role of redox-active axial ligands of metal porphyrins adsorbed at solid-liquid interfaces in a liquid-STM setup.

In a liquid-STM setup environment, the redox behavior of manganese porphyrins was studied at various solid–liquid interfaces. In the presence of a solution of Mn(III)Cl porphyrins in 1-phenyloctane, which was placed at a conductive surface, large and constant additional currents relative to a set tunneling current were observed, which varied with the magnitude of the applied bias voltage. These currents occurred regardless of the type of surface (HOPG or Au(111)) or tip material (PtIr, Au or W). The additional currents were ascribed to the occurrence of redox reactions in which chloride is oxidized to chlorine and the Mn(III) center of the porphyrin moiety is reduced to Mn(II). The resulting Mn(II) porphyrin products were identified by UV–vis analysis of the liquid phase. For solutions of Mn(III) porphyrins with non-redox active acetate instead of chloride axial ligands, the currents remained absent.

The influence of different metal atoms on the performance of metalloporphyrin-based sensor reaction with propanol

ABSTRACT Density functional theory (DFT) method was carried out to investigate the molecular interaction between metalloporphyrin-based sensor and propanol. The relative energies were used to determine the most stable state of metalloporphyrin and its complexes at three different spin states for further theoretical studies. The low-spin states were found to be the most stable states for cobalt porphyrin (CoP), tin porphyrin (Sn), and zinc porphyrin (ZnP) before exposure to propanol and CoP, SnP, ZnP, iron porphyrin (FeP), ruthenium porphyrin (RuP) after exposure to propanol. The intermediate-spin state was found to be the most stable states for the other metalloporphyrins and their complexes, except for manganese porphyrin (MnP) after exposure to propanol. The calculated binding energies were shown the following order for metalloporphyrin-based sensor-binding propanol: MnP>ZnP>CoP>RuP>SnP>FeP>AgP>CuP. This calculated result may be useful for the theoretical design of metalloporphyrin-based sensor for propanol determination and perhaps other analyte.

Manganese Porphyrin Interface Engineering in Perovskite Solar Cells

An interfacial engineering approach was adopted in order to optimize the photovoltaic parameters and the stability of n-i-p planar perovskite solar cells (PSCs). A thin manganese (Mn) porphyrin [(T...