Simple Manganese Salts Research Articles

Synthetic routes to manganese oxoborate and correlations between experimental parameters and properties

This study examines manganese oxoborate synthesis in three different routes and the role of process parameters on structure and morphology of the products. Borax or boric acid and simple manganese salts were used as raw materials. In this regard, the samples prepared by hydrothermal, solid-state, and solution combustion methods were characterized by powder X-ray diffraction (XRD), vibrational spectroscopy (FT-IR and Raman), thermal analysis (DSC and TGA), scanning and transmission electron microscopy (SEM and TEM), chemical analysis and BET surface area measurements. It was found that all three strategies yielded warwickite-type Mn2OBO3 nanoparticles, but with significant changes in morphology, size, and surface characteristics. The hydrothermal approach has proven to be a general approach for synthesizing manganese oxoborate nanorods at pH 7.5. Solution combustion technique appeared the most practical and promising not only as a time-saving route but also in the production of ca. 100 nm, quasi-spherical, mesoporous manganese oxoborate nanoparticles.

Electrochemical water oxidation by simple manganese salts

Recently, it has been great efforts to synthesize an efficient water-oxidizing catalyst. However, to find the true catalyst in the harsh conditions of the water-oxidation reaction is an open area in science. Herein, we showed that corrosion of some simple manganese salts, MnCO3, MnWO4, Mn3(PO4)2 · 3H2O, and Mn(VO3)2 · xH2O, under the water-electrolysis conditions at pH = 6.3, gives an amorphous manganese oxide. This conversion was studied with X-ray absorption spectroscopy (XAS), as well as, scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDXS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), spectroelectrochemistry and electrochemistry methods. When using as a water-oxidizing catalyst, such results are important to display that long-term water oxidation can change the nature of the manganese salts.

Water oxidation by simple manganese salts in the presence of cerium(iv) ammonium nitrate: towards a complete picture.

For the first time, using scanning electron microscopy, transmission electron microscopy, X-ray absorption near edge structure and extended X-ray absorption fine structure X-ray diffraction, it is showed that MnCO3, MnWO4, Mn3(PO4)2·3H2O, MnS and Mn(VO3)2·xH2O under the water-oxidation conditions and in the presence of cerium(iv) ammonium nitrate, are converted to Mn oxide without a high-range order. A mechanism is proposed for such conversion and as Mn oxide is an efficient water-oxidizing catalyst, it is thus a candidate as a contributor to the observed catalytic activity.

Manganese-Catalyzed Directed Methylation of C(sp2)-H Bonds at 25 °C with High Catalytic Turnover.

We report here a manganese-catalyzed C-H methylation reaction of considerable substrate scope, using MeMgBr, a catalytic amount of MnCl2·2LiCl, and an organic dihalide oxidant. The reaction features ambient temperature, low catalyst loading, typically 1%, high catalytic turnover reaching 5.9 × 103, and no need for an extraneous ligand and illustrates a unique catalytic use of simple manganese salts for C-H activation, which so far has relied on catalysis by manganese carbonyls.

Supertetrahedral icosanuclear and ring-like decanuclear mixed valent manganese(ii/iii) triethanolamine clusters

The synthesis and characterisation of three new mixed-valent manganese clusters [Mn(II)₄Mn(III)₁₆O₁₂(OH)₄(tea)₈(chp)₄]·6MeOH·4H₂O (1), [Mn(II)₆Mn(III)₄(teaH)₄(teaH₂)₂(tpaa)₆(F)₈]·2Et₂O·4MeCN (2) and [Mn(II)₆Mn(III)₄(teaH)₄(teaH₂)₂(2-bpca)₆(F)₈]·4MeCN (3) are reported. They were obtained by the reaction of simple manganese salts with triethanolamine (teaH₃), triethylamine (NEt₃) and the appropriate co-ligand. In the case of 1, 6-chloro-2-hydroxypyridine (Hchp) was used, for 2, triphenylacetic acid (tpaa) and 3, 2-biphenylcarboxylic acid (2-bpca). The core of 1 is a Mn₂₀ supertetrahedron, while the cores of 2 and 3 are identical and have distorted ring-like topologies. Variable-temperature, solid-state DC and AC magnetic studies were performed on 1-3 in the 2-300 K (DC) and 2-18 K (AC) ranges. Cluster 1 has a S = 9 ground state with excited S states, larger in value than 9, close in energy. No SMM features were apparent in 1. In contrast, clusters 2 and 3, with S = 12 or 13 ground states, and with excited S levels of lower value than 12 lying close in energy, do show SMM features, albeit below 2 K in their AC out-of-phase, frequency dependent data.

Metal ion-catalyzed oxidative degradation of Orange II by H2O2. High catalytic activity of simple manganese salts

In an effort to develop new routes for the clean oxidation of non-biodegradable organic dyes, a detailed study of some environmentally friendly Mn(II) salts that form very efficient in situcatalysts for the activation of H2O2 in the oxidation of substrates such as Orange II under mild reaction conditions, was performed. The studied systems have advantages from the viewpoint of green chemistry in that simple metal salts can be used as very efficient catalyst precursors and H2O2 is used as a green oxygen donor reagent. Oxidations were carried out in a glass reactor over a wide pH range in aqueous solution at room temperature. Under optimized conditions it was possible to degrade Orange II in a carbonate buffer solution in less then 100 s using 0.01 M H2O2 in the presence of only 2 × 10−5 M Mn(II) salt. To gain insight into the manganese catalyzed oxidation mechanism, the formation of the active catalyst was followed spectrophotometrically and appears to be the initiating step in the oxidative degradation of the dye. High valent manganese oxo species are instable in the absence of a stabilizing coordinating ligand and lead to a rapid formation of catalytically inactive MnO2. In this context, the role of the organic dye and HCO3− as potential stabilizing ligands was studied in detail. In situUV-Vis spectrophotometric measurements were performed to study the effect of pH and carbonate concentration of the buffer solution on the formation of the catalytically active species. Electrochemical measurements and DFT (B3LYP/LANL2DZp) calculations were used to study the in situ formation of the catalytic species. The catalytic cycle could be repeated several times and demonstrated an excellent stability of the catalytic species during the oxidation process. A mechanism that accounts for the experimental observations is proposed for the overall catalytic cycle.

Using Elevated Temperature as an Assay to Determine the Importance of Various SODs and the Life Extending Properties of Various Manganese Salts in C. elegans

C. elegans have a similar aging mechanism as humans, including the presence of superoxide scavenging enzymes, SODs (Superoxide Dismutase). This study focused only on two out of five different forms of SODs, a manganese SOD (SOD-3) and a copper-zinc SOD (SOD-4), to uncover the most important one for combating oxidative stress. In addition, this current study extended on the previous findings that ionic manganese supplementation provides life-span extending benefit, to uncover a preferred chemical form of manganese that has superior efficacy compared to previously utilized MnSO4. The various worm strains were grown as a synchronous population from eggs at 22°C for 48 hours. They were then subjected to thermal stress at 35°C, which elevates free radical levels in vivo to a lethal limit. The results showed that a form of manganese SOD (SOD-3) is vital in combating oxidative stress, that MnSO4 supplementation rescued the reduced thermotolerance seen in SOD-3 knockout worms and that MnSO4 is the preferential form for worm supplementation studies compared to other simple salts based on thermotolerance assay. Future studies will include manganese containing complexes, some of which are known to have antioxidant properties, to examine if simple manganese salts can be as efficacious as the complexes using both thermotolerance and life-span as assays.

Synthesis and in vitro anti-microbial activity of manganese (II) complexes of 2,2-dimethylpentanedioic and 3,3-dimethylpentanedioic acid: X-ray crystal structure of [Mn(3dmepda)(phen) 2] · 7.5H 2O (3dmepdaH 2=3,3-dimethylpentanedioic acid and phen=1,10-phenanthroline)

Reactions of 2,2-dimethylpentanedioic acid(2dmepdaH 2) and 3,3-dimethylpentanedioic acid (3dmepdaH 2) with Mn(CH 3COO) 2 · 4H 2O yield the soluble complexes [Mn(2dmepda)] · 1.5H 2O ( 1) and [Mn(3dmepda)] · H 2O ( 2). Complex 1 reacts with ethanolic solutions of 2,2 ′-bipyridine or 1,10-phenanthroline to give [Mn 2(2dmepda) 2(bipy)] · H 2O ( 3) and [Mn(2dmepda)(phen)] ( 4), respectively. Similar reactions of 2 with these ligands generated [Mn 2(3dmepda) 2(bipy) 3] · 5H 2O ( 5) [Mn(3dmepda)(phen) 2] · 7.25H 2O ( 6). The molecular structure of 6 was determined by X-ray crystallography. The asymmetric unit contains two [Mn(3dmepda)(phen) 2] units with 14.5 waters of crystallisation. The two manganese complexes are of very similar structure. In each case the manganese atom is ligated by four nitrogen atoms from two chelating phen molecules and two oxygen atoms, one from each of the carboxylates moieties of the 3dmepda 2− ligand. Thus, the two carboxylate functions of the two 3dmepda 2− dianionic ligands are essentially monodentate. The 2,2- and the 3,3-dimethylpentanedioate complexes, the metal free ligands and a number of simple manganese salts were each tested for their ability to inhibit the growth of Candida albicans. Only the “metal free” 1,10-phenanthroline and its 2,2- and the 3,3-dimethylpentanedioate complexes exhibit fungitoxic activity.

Oxidative DNA damage from sulfite autoxidation catalyzed by manganese(III)

A series of manganese(II) and manganese(III) salts and oxides were investigated for their ability to catalyze the autoxidation of sulfite resulting in oxidative damage to DNA. Experiments directed at identifying the reactive intermediates responsible for DNA oxidation included the trapping of a sulfite radical adduct during EPR studies, alcohol quenching studies of free radical intermediates, comparisons of relative reactivities toward conversion of Type I to Type II plasmid DNA and cleavage of a duplex DNA restriction fragment. The studies support previous work on the mechanism of manganese(III)-catalyzed sulfite autoxidation and provide evidence that simple manganese salts are capable of mediating substantial DNA damage in conjunction with sulfite.

Synthesis and fungitoxic activity of manganese(II) complexes of fumaric acid: X-ray crystal structures of [Mn(fum)(bipy)(H 2O)] and [Mn(Phen) 2(H 2O) 2](fum)·4H 2O (fumH 2=fumaric acid; bipy=2,2′-bipyridine; phen=1,10-phenanthroline)

The reaction of fumaric acid with Mn(CH 3COO) 2·4H 2O gives the polymeric complex {Mn(fum)} n ( 1). Complex 1 reacts with 2,2′-bipyridine in ethanol to yield [Mn(fum)(bipy)(H 2O)] n ( 2). Reaction of 1 with 2 equiv. of 1,10-phenanthroline produces [Mn 2(fum) 2(phen) 2.5]·3H 2O ( 3) and [Mn(phen) 2(H 2O) 2](fum)·4H 2O ( 4). The molecular structures of 2 and 4 were determined by X-ray crystallography. In 2 the fumarate anions link the manganese ions so that each is seven coordinate, being bonded to a bidentate bipyridine, two bidentate carboxylates and one H 2O molecule. In 4 the asymmetric unit contains a [Mn(phen) 2(H 2O) 2] 2+ cation, half of each of two independent fumarate anions and four lattice H 2O molecules. The cations and anions are interconnected by water molecules hydrogen bonded to both coordinated water molecules and fumarate oxygens. The fumarate complexes, the metal free ligands and a number of simple manganese salts were each tested for their ability to inhibit the growth of Candida albicans. Only the ‘metal free’ 1,10-phenanthroline and its fumarate complexes exhibit fungitoxic activity

Potential use of simple manganese salts as antioxidant drugs in horses

SUMMARY The scavenging of superoxide radicals by endogenous and therapeutically administered superoxide dismutases may prevent superoxide-mediated oxidative stress leading to lipid peroxidation, membrane lysis, and cell death in a wide variety of normal and pathologic states. Simple inorganic manganous salts such as MnCl2 also have superoxide dismutase-like activity and are extremely inexpensive, compared with enzymatic superoxide dismutase preparations. In this study, we explored the use of Mn salts as antioxidant drugs. We used the percentage of inhibition of nitroblue tetrazolium reduction by superoxide as a measure of the amount of superoxide dismutase-like activity. We found concentration-related increases in superoxide scavenging activity in simple buffer solutions upon addition of 1.25, 2.5, and 5.0 μM MnSO4. To determine whether Mn salts can inhibit oxidative damage in tissues, we used an in vitro model of lipid peroxidation in ischemic and reoxygenated rat liver slices. Concentrations of 10, 100, and 1000 μmoles MnCl2/L of buffer significantly decreased indicators of lipid peroxidation believed to be initiated by intracellular superoxide. We then determined the effectiveness of MnCl2 as a superoxide scavenger in conscious horses by measuring the superoxide scavenging ability of equine plasma before and during intravenous infusions of 1.0 L volumes of 0.9% slaine solution containing 0, 12.5, or 25 mM MnCl2. Plasma Mn concentrations, which were determined by atomic absorption spectrophotometry, increased as a function of time and dose. Intravenously administered MnCl2 concomitantly produced dose-related increases in superoxide scavenging ability of equine plasma at 15, 30, 45, and 60 minutes after the onset of infusion, compared with preinfusion control values. Heart rate and blood pressure of the treated horses, which were monitored to measure toxicity of MnCl2, gradually increased in both treatment groups. Clinical adverse effects of MnCl2 administration included defecation, pawing, hyperexcitability, flank watching, and sweating. The results of this study indicate that simple Mn salts may scavenge superoxide radicals in vivo with minimal adverse reactions and at a trivial cost.