Manganese complexes phosphates

The electrochemistry of oxo-bridged manganese complexes in aqueous solution is characterized by coupled electron and proton-transfer reactions. The cyclic voltammetric behavior of [Mn2 02(phen)4] + in aqueous pH 4.5 phosphate buffer is illustrated in Fig. 12 [97]. It is of interest to compare this result with that obtained for the same complex dissolved in CH3CN (Fig. 9). Two one-electron reactions are observed in each case. However, these correspond to Mn(IV,IV) Mn(IV,III) and Mn(IV,III) Mn(III,III) reductions in the nonaqueous solvent and to Mn(IV,III) Mn(III,III) and Mn(III,III) Mn(III,II) reductions in... 

Fig. 5 Vertical distribution of temperature (T), salinity (S), dissolved oxygen (O2), dissolved manganese (Mn diss), particulate manganese (Mn part), bivalent iron (Fe(II)), trivalent iron (Fe(III)), phosphate (P04), manganese complex (Mn com), organic phosphorus (Porg), and polyphosphate (Ppoly) at a station near Gelendzhik (St. 2618, September, 2006). Concentrations of chemical parameters are in xM. Distributions are plotted versus depth (m) at the top and versus density (og, kgm-3) at the bottom...

Other lithium-bearing minerals are spodumene, a double silicate of lithium and aluminium, containing about 3 8 per cent, of lithium triphyllite, a complex phosphate of lithium, iron, and manganese, with about 2 2 per cent, of lithium and amblygonite and montebrasite, fluo-phosphates of lithium and aluminium, with about 2 35 per cent, of lithium, both rare minerals. 

The chemical shift of the phosphorus resonance of various nucleotides has been studied as a function of pH in the presence and absence of RNase A. The signal shifts upheld on protonation of the phosphate and the apparent pATa of the phosphate group in 2 -CMP complex with RNase is the same as the pATa of histidine-119 in this enzyme as determined by n.m.r. From n.m.r. relaxation rates for the ternary complex manganese(n)-phosphate-E. coli alkaline phosphatase, it has been concluded that an outer-sphere complex is formed which has a shorter lifetime than the enzyme turnover rate. The latter conclusion is consistent with the participation of the complex in the enzymic reaction. 

Precipitation is often applied to the removal of most metals from wastewater including zinc, cadmium, chromium, copper, fluoride, lead, manganese, and mercury. Also, certain anionic species can be removed by precipitation, such as phosphate, sulfate, and fluoride. Note that in some cases, organic compounds may form organometallic complexes with metals, which could inhibit precipitation. Cyanide and other ions in the wastewater may also complex with metals, making treatment by precipitation less efficient. A cutaway view of a rapid sand filter that is most often used in a municipal treatment plant is illustrated in Figure 4. The design features of this filter have been relied upon for more than 60 years in municipal applications. 

Determination of uranium with cupferron Discussion. Cupferron does not react with uranium(VI), but uranium(IV) is quantitatively precipitated. These facts are utilised in the separation of iron, vanadium, titanium, and zirconium from uranium(VI). After precipitation of these elements in acid solution with cupferron, the uranium in the filtrate is reduced to uranium(IV) by means of a Jones reductor and then precipitated with cupferron (thus separating it from aluminium, chromium, manganese, zinc, and phosphate). Ignition of the uranium(IV) cupferron complex affords U308. 

Brewer and Spencer [428] have described a method for the determination of manganese in anoxic seawaters based on the formulation of a chromophor with formaldoxine to produce a complex with an adsorption maximum at 450 nm. Sulfide (50 xg/l), iron, phosphate (8 ig/l), and silicate (100pg/l) do not interfere in this procedure. The detection limit is 10 pg/1 manganese. 

Manganese(II)-A/, A/r -dipyridoxylethylenediamine-A/r, AT-diacetate 5,5 -bis(phosphate) 75 (DPDP) is clinically used for enhancing contrast in the liver (detection of hepatocellular carcinomas) (312). Some dissociation of Mn(II) appears to occur in the liver, and enhancement can also be obtained in functional adrenal tissues (313). Manganese(II)-tetrasulfonated phthalocyanine also shows tumor localization properties and is a more efficient relaxation agent than the analogous Gd(III) complexes (314). 

The most direct evidence for surface precursor complex formation prior to electron transfer comes from a study of photoreduc-tive dissolution of iron oxide particles by citrate (37). Citrate adsorbs to iron oxide surface sites under dark conditions, but reduces surface sites at an appreciable rate only under illumination. Thus, citrate surface coverage can be measured in the dark, then correlated with rates of reductive dissolution under illumination. Results show that initial dissolution rates are directly related to the amount of surface bound citrate (37). Adsorption of calcium and phosphate has been found to inhibit reductive dissolution of manganese oxide by hydroquinone (33). The most likely explanation is that adsorbed calcium or phosphate molecules block inner-sphere complex formation between metal oxide surface sites and hydroquinone. 

A convenient enantioselective catalytic oxidation of a variety of differently substituted, cyclic (E) and acyclic (Z)-enol phosphates with (salen)manganese(III) complex has been reported. The influence of electronic and steric effects of the enol phosphate substituents on the stereoselectivity of oxidation has been studied.50... 

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